Health Initiative Dietary Modification Research Articles

Causal effect estimation for competing risk data in randomized trial: adjusting covariates to gain efficiency

The double-blinded randomized trial is considered the gold standard to estimate the average causal effect (ACE). The naive estimator without adjusting any covariate is consistent. However, incorporating the covariates that are strong predictors of the outcome could reduce the issue of unbalanced covariate distribution between the treated and controlled groups and can improve efficiency. Recent work has shown that thanks to randomization, for linear regression, an estimator under risk consistency (e.g. Random Forest) for the regression coefficients could maintain the convergence rate even when a nonparametric model is assumed for the effect of covariates. Also, such an adjusted estimator will always lead to efficiency gain compared to the naive unadjusted estimator. In this paper, we extend this result to the competing risk data setting and show that under similar assumptions, the augmented inverse probability censoring weighting (AIPCW) based adjusted estimator has the same convergence rate and efficiency gain. Extensive simulations were performed to show the efficiency gain in the finite sample setting. To illustrate our proposed method, we apply it to the Women's Health Initiative (WHI) dietary modification trial studying the effect of a low-fat diet on cardiovascular disease (CVD) related mortality among those who have prior CVD.

Abstract P492: Polygenic Risk for Obesity and Race Modify the Effect of a Low Fat Dietary Clinical Trial on Weight Loss

Introduction: Research populations harbor innate and acquired characteristics that can introduce substantial treatment response heterogeneity. Weight loss interventions show this variability, likely due to behavioral and physiological characteristics. Genetic risk for obesity is a potential but largely unexplored factor in weight loss trials. We examined whether genetic risk for obesity modified the effect of a low-fat diet on weight change in a randomized controlled trial. Methods: A data from the Women’s Health Initiative Dietary Modification Trial, including 10,353 postmenopausal women aged 50-79 with genotype data [63% European American (EAs), 37% African American (AAs)] were randomized into control and low-fat diet groups. The outcome was visit-specific weight difference (kg) from baseline. The Polygenic Risk Score of body mass index (PRS BMI ) was computed using the PRS-CS method and an independent trans-ancestry genome-wide association study of BMI (N = ~ 2M; 79 % EAs and 4 % AAs). We operationalized PRS BMI as a binary variable, distinguishing individuals in the 95 th percentile from the remaining individuals. Association was tested using generalized estimated equations with a 3-way interaction term (PRS х randomization х time), adjusting for 10 principal components, age, baseline BMI, and follow-up status. Analyses were performed separately by race/ethnicity, because body weight is influenced by ancestral diversity, which affects both linkage disequilibrium, PRS effect sizes, and cultural factors (e.g., racism). Results: Baseline, we had 6,473 EAs (mean age: 65.4 ± 6.6 years, mean BMI: 29.5 ± 6.5 kg/m 2 ) and 3,880 AAs (mean age: 60.9 ± 6.7years, mean BMI: 32.1 ± 6.8 kg/m 2 ) and mean follow-up was 6.0 ± 1.8 years. PRS BMI explained 12% of the variance in the baseline BMI measure in EAs and 8% in AAs. During the first year of intensive dietary intervention (18 sessions/yr), the low-fat diet group experienced 2.1 kg and 1.1 kg weight loss in European and AAs respectively, with no differences in PRS BMI . During years 1-7 with reduced intervention intensity (4 sessions/yr), the rate of weight change in both race/ethnic groups were modified by PRS BMI , although in different directions. EAs with high PRS (95 th percentile) in the intervention group rebounded towards initial weight (0.35 kg/year, p<0.001) nearly twice as fast as those women with PRS < 95 th percentile (0.19 kg/year, p<0.001). Conversely, high PRS African American women in the intervention group maintained their weight loss without rebound (-0.10 kg/year, p=0.48), distinctly different from those with PRS < 95 th percentile, who gained 0.25 kg annually (p<0.001). Conclusions: Impact of long-term low-fat dietary intervention on weight change was modified by genetic risk and race/ethnicity. Genetic predisposition and other contextual factors may be considered in the design and analysis of relevant clinical trials.

Dietary Intervention Favorably Influences Physical Functioning: The Women’s Health Initiative Randomized Dietary Modification Trial

BackgroundIn the Women’s Health Initiative Dietary Modification randomized trial, the dietary intervention reduced breast cancer mortality by 21% (P = .02) and increased physical activity as well. ObjectiveTherefore, the aim was to examine whether or not these lifestyle changes attenuated age-related physical functioning decline. DesignIn a randomized trial, the influence of 8 years of a low-fat dietary pattern intervention was examined through 20 years of cumulative follow-up. Participants and settingFrom 1993 to 1998, 48,835 postmenopausal women, ages 50 to 79 years with no prior breast cancer and negative baseline mammogram were randomized at 40 US clinical centers to dietary intervention or usual diet comparison groups (40 out of 60). The intervention significantly reduced fat intake and increased vegetable, fruit, and grain intake. Main outcome measuresIn post hoc analyses, physical functioning, assessed using the RAND 36-Item Short Form Health Survey, evaluated quality or limitations of 10 hierarchical physical activities. Longitudinal physical functioning, reported against a disability threshold (when assistance in daily activities is required) was the primary study outcome. Statistical analyses performedSemiparametric linear mixed effect models were used to contrast physical functioning trajectories by randomization groups. ResultsPhysical functioning score, assessed 495,317 times with 11.0 (median) assessments per participant, was significantly higher in the intervention vs comparison groups through 12 years of cumulative follow-up (P = .001), representing a reduction in age-related functional decline. The intervention effect subsequently attenuated and did not delay time to the disability threshold. Among women in the dietary intervention vs comparison groups, aged 50 to 59 years, who were physically inactive at entry, a persistent, statistically significant, favorable influence on physical functioning with associated delay in crossing the disability threshold by approximately a year was seen (P value for interaction = .007). ConclusionsIn the Women’s Health Initiative Dietary Modification randomized trial, a dietary intervention that significantly reduced breast cancer mortality also significantly reduced age-related functional decline through 12 years, which was attenuated with longer follow-up.

Effect of Low-Fat Dietary Modification on Incident Open-Angle Glaucoma

We tested whether dietary modification (DM) altered the risk for incident primary open-angle glaucoma (POAG). Secondary analysis of a randomized intervention trial. We linked Medicare claims data to 45 203 women in the Women's Health Initiative Dietary Modification Trial, of which 23 776 participants were enrolled in fee-for-service Medicare Part B and had physician claims. Women were randomized to follow either DM (a low-fat diet, with increased vegetable, fruit, and grain intake) or their usual diet without modification. Nine thousand three hundred forty women were randomized to the DM intervention, whereas 13 877 women were randomized to the control group. Our analyses were based on an intention-to-treat design, with a follow-up to the end of continuous Medicare coverage, death, or the last claims date (12/31/2018), whichever occurred first. Primary open-angle glaucoma was defined as the first claim with the International Classification of Diseases, Ninth or Tenth Revision, codes. Dietary data were assessed using a food frequency questionnaire. We used Cox proportional hazards models to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for risk of POAG. Subgroup analyses were performed with P values for interaction. After exclusion of women with Medicare-derived glaucoma before randomization, the final analysis included 23 217 women (mean age, 64.4 ± 5.8 years). Baseline characteristics were balanced between the intervention and control groups. Primary open-angle glaucoma incidence was 11.1 per 1000 woman-years (mean follow-up, 11.6 ± 7.4 years; mean DM duration, 5.2 ± 3.2 years). We found no overall benefit of DM in reducing incident POAG (HR, 1.04; 95% CI, 0.96-1.12). Race and participant age did not modify this relation (P = 0.08 and P = 0.24 for interaction, respectively). In further analysis of baseline nutrient and food intake stratified by quartile groups, risk of open-angle glaucoma (OAG) in DM participants in the lowest quartile group for percentage calories (kilocalories) from total fat (33.8 or lower) was increased (HR, 1.22; 95% CI, 1.05-1.41; P = 0.007 for interaction). Analysis suggests that DM in participants in the lowest quartile group for percentage calories from total fat at baseline increased the risk of incident OAG among women regardless of age or race. Proprietary or commercial disclosure may be found after the references.

Long-term dietary intervention influence on physical activity in the Women's Health Initiative Dietary Modification randomized trial.

In the Women's Health Initiative (WHI) Dietary Modification (DM) randomized trial, dietary intervention significantly reduced breast cancer mortality (P = 0.02). In observational studies, physical activity is associated with lower breast cancer incidence. Currently, dietary intervention influence on other health-related behaviors is unknown. Therefore, we evaluated whether the WHI dietary intervention influenced self-directed physical activity. Of 48,835 postmenopausal women, 19,541 were randomized to dietary intervention (18 nutritionist-led group sessions first year, then quarterly sessions throughout 8.5years [median] intervention) and 29,294 to a usual diet comparison (written health-related materials only). Neither randomization group received specific or ongoing instructions to increase physical activity. Episodes per week of moderate or vigorous recreational physical activity (MVPA) were serially reported. Marginal longitudinal logistic regression models were used to assess physically inactive (MVPA = 0) or physically active (MVPA > 0) participants by randomization group. Marginal Poisson regression models estimated mean weekly MVPA. At entry, 45.6% of all participants reported physical inactivity (MVPA = 0). In 43,760 women with MVPA information, throughout 15.9years (median) cumulative follow-up, dietary intervention group participation was associated with 7% lower physical inactivity rate (odds ratio [OR] 0.93, 95% confidence interval [CI] 0.91, 0.95, P < 0.001) and a 4% higher mean MVPA (ratio of means [RM] 1.04 95% CI 1.02, 1.06, P < 0.001), relative to the comparison group. In a randomized trial setting, a low-fat dietary pattern intervention was associated with a long-term, favorable influence on self-directed recreational physical activity. NCT00000611.

Low-fat dietary pattern reduces urinary incontinence in postmenopausal women: post hoc analysis of the Women's Health Initiative Diet Modification Trial

BACKGROUNDUrinary incontinence affects >40% of women in the United States, with an annual societal cost of >$12 billion and demonstrated associations with depressive symptoms, social isolation, and loss of work productivity. Weight has been established as an exposure that increases urinary incontinence risk and certain dietary components have been associated with urinary incontinence symptoms. We hypothesized that diet plays a key role in the association between weight and urinary incontinence in US women.OBJECTIVEThis study aimed to examine the effect of a low-fat diet on urinary incontinence in postmenopausal women as a post hoc analysis of a randomized controlled trial of diet modification.STUDY DESIGNThis was a post hoc analysis of the Women's Health Initiative Dietary Modification randomized controlled trial of 48,835 postmenopausal women from 40 US centers assigned to a dietary intervention (20% energy from fat, 5 fruits or vegetable servings, and 6 whole grain servings daily and an intensive behavioral modification program) or to the usual diet comparison group. The outcome was urinary incontinence at 1 year.RESULTSOf the participants, 60% were randomized to the usual diet comparison group and 40% to the dietary modification intervention. After adjusting for weight change, women assigned to the dietary modification intervention were less likely to report urinary incontinence (odds ratio, 0.94; 95% confidence interval, 0.90–0.98; P=.003), more likely to report urinary incontinence resolution (odds ratio, 1.11; 95% confidence interval, 1.03–1.19; P=.01), and less likely to develop urinary incontinence (odds ratio, 0.92; 95% confidence interval, 0.87–0.98; P=.01) in adjusted models.CONCLUSIONDietary modification may be a reasonable treatment for postmenopausal women with incontinence and also a urinary incontinence prevention strategy for continent women. Our results provide evidence to support a randomized clinical trial to determine whether a reduced fat-intake dietary modification is an effective intervention for the prevention and treatment of urinary incontinence. In addition to providing further insights into mechanisms of lower urinary tract symptoms, these findings may have a substantial impact on public health based on the evidence that diet seems to be a modifiable risk factor for urinary incontinence.

Breast Cancer Prevention: Time for Change.

Agency breast cancer prevention guidelines for other than hereditary cancers have not materially changed in 20 years; endocrine-targeted agents (then, tamoxifen; now, adding raloxifene and aromatase inhibitors) reduce good prognosis estrogen receptor (ER)-positive, progesterone receptor (PR)-positive cancers without reducing deaths from breast cancer. Across three tamoxifen placebo-controlled prevention trials (N = 23,360) begun almost 30 years ago, although there were 226 fewer breast cancer cases, there were nine more deaths from breast cancer in the tamoxifen groups. Following clinical advances, currently more than half of breast cancer cases are solved problems with extremely low risk of death. As endocrine-targeted agents commonly prevent these cancers, widespread implementation of current prevention strategies may not reduce deaths from breast cancer. Compared with other breast cancers, ER-positive, PR-negative cancers and triple-negative cancers have inferior survival (90.6% v 83.8% v 78.1%, respectively; P < .001). Against this background, in the Women's Health Initiative Dietary Modification randomized trial (N = 48,835), ER-positive, PR-negative cancers were statistically significantly reduced in the intervention group (hazard ratio, 0.77; 95% CI, 0.64 to 0.94) and deaths from breast cancer were reduced 21% (P = .02). In the Women's Health Initiative randomized, placebo-controlled trial evaluating conjugated equine estrogen (N = 10,739), ER-positive, PR-negative cancers were statistically significantly reduced in the intervention group (hazard ratio, 0.44; 95% CI, 0.27 to 0.74) and deaths from breast cancer were reduced 40% (P = .04). These findings suggest that reexamination of breast cancer risk reduction strategies and clinical practice is needed.

Low-Fat Dietary Modification and Risk of Ductal Carcinoma In Situ of the Breast in the Women's Health Initiative Dietary Modification Trial.

Results of observational studies of the association between dietary fat and risk of invasive breast cancer have been inconsistent. In the Women's Health Initiative dietary modification (DM) randomized trial designed to lower fat intake, the intervention was not associated with a statistically significant reduction of overall breast cancer risk. However, the DM association with risk of ductal carcinoma in situ (DCIS) of the breast, a putative breast cancer precursor, has not been reported. A total of 48,835 postmenopausal women, ages 50-79 years at enrollment, with no breast cancer history and ≥32% of total energy intake from fat, were randomly assigned either to a dietary intervention (n = 19,541) designed to reduce total fat intake to 20% of energy and to increase vegetable, fruit, and grain consumption, or to a comparison group (n = 29,294). Cox proportional hazards models were used to estimate HRs and 95% confidence intervals for the association between the intervention and DCIS risk. During 18.7 years (median) cumulative follow-up, including intervention (∼8.7 years) and post-intervention phases (∼13.0 years), 817 DCIS cases were ascertained. No evidence of an association between the DM intervention and DCIS risk was observed overall, or by trial phase (intervention and post-intervention). Similarly, no associations were found in subgroups defined by potential risk factors for DCIS. DM aiming to reduce fat intake was not associated with altered risk of DCIS. These results do not provide evidence of an association between dietary fat reduction and the risk of DCIS among postmenopausal women.

Dietary intervention influence on physical activity in the Women’s Health Initiative randomized Dietary Modification trial.

10511 Background: In the Women’s Health Initiative (WHI) Dietary Modification (DM) randomized trial, after 8.5 years dietary intervention and 19.5 years cumulative (median) follow-up, dietary intervention participation was associated with a statistically significantly 22% lower breast cancer mortality (P = 0.02). In observational studies, physical activity has been associated with lower breast cancer risk with emerging results now indicating, compared to inactivity, any increase in physical activity has health benefits. Currently, longitudinal data on whether an intervention targeting dietary change influences other health-related behaviors as a gateway effect is limited. To evaluate whether randomization to a dietary intervention was associated with self-directed change in physical activity. Methods: In the WHI DM trial, 48,835 postmenopausal women, ages 50-79 years, with no prior breast cancer and baseline normal mammogram were randomized at 40 US clinical centers to a dietary intervention (19,541) or a comparison group. Dietary goals were to reduce fat intake to 20% of energy and increase intake of vegetable, fruit, and grains addressed in 18 group sessions in year 1 then quarterly. Neither randomization group received specific or ongoing instructions to increase physical activity, but physical activity was referenced in written materials given to the intervention groups in 7 of the 56 sessions. Episodes per week of moderate or vigorous recreational physical activity (MVPA) were collected at baseline and serially through 15.9 years follow-up by self-report questionnaire. Marginal longitudinal logistic regression models were used to assess physically inactive (MVPA = 0) or physically active (MVPA &gt; 0) participants by randomization group. Marginal Poisson regression models estimated mean weekly MVPA by randomization group. Results: 45.6% of participants reported 0 MVPA at baseline which largely persisted throughout follow-up. During cumulative follow-up, relative to the comparison group, dietary intervention group participation was associated with 7% lower physical inactivity rate (odds ratio [OR] 0.93 95% confidence interval [CI] 0.91, 0.95, P &lt; 0.001) and a 4% higher mean MVPA (ratio of means [RM] 1.04 95% CI 1.02, 1.06, P &lt; 0.001). The association between dietary intervention participation with higher physical activity level was stronger with increasing BMI (P-interaction 0.01) and for women with waist circumference ≥ 88 cm (P-interaction 0.02). Conclusions: In conclusion, in a randomized trial setting, a low-fat dietary pattern intervention was associated with a significantly lower physical inactivity rate and significantly higher moderate and vigorous physical activity level which could be associated with health benefits. Clinical trial information: NCT00000611 .

Low-fat dietary pattern and breast cancer mortality by metabolic syndrome components: a secondary analysis of the Women's Health Initiative (WHI) randomised trial.

In the Women's Health Initiative (WHI) dietary modification (DM) randomised trial, the low-fat dietary intervention reduced deaths from breast cancer (P = 0.02). Extending these findings, secondary analysis examined dietary intervention influence on breast cancer mortality by metabolic syndrome (MS) components. In total, 48,835 postmenopausal women with no prior breast cancer were randomised to a low-fat dietary intervention or comparison groups. Four MS components were determined at entry in 45,833 participants: (1) high waist circumference, (2) high blood pressure, (3) high cholesterol and (4) diabetes history. Forest plots of hazard ratios (HRs) were generated with P-values for interaction between randomisation groups and MS component score. Primary outcome was death from breast cancer by metabolic syndrome score. HRs and 95% confidence intervals (CI) for dietary intervention influence on death from breast cancer were with no MS components (n = 10,639), HR 1.09, 95% CI 0.63-1.87; with 1-2 MS components (n = 30,948), HR 0.80, 95% CI 0.62-1.02; with 3-4 MS components (n = 4,246), HR 0.31, 95% CI 0.14-0.69 (interaction P = 0.01). While postmenopausal women with 3-4 MS components were at higher risk of death from breast cancer, those randomised to a low-fat dietary intervention more likely had reduction in this risk. ClinicalTrials.gov (NCT00000611).

Regression calibration to correct correlated errors in outcome and exposure.

Measurement error arises through a variety of mechanisms. A rich literature exists on the bias introduced by covariate measurement error and on methods of analysis to address this bias. By comparison, less attention has been given to errors in outcome assessment and nonclassical covariate measurement error. We consider an extension of the regression calibration method to settings with errors in a continuous outcome, where the errors may be correlated with prognostic covariates or with covariate measurement error. This method adjusts for the measurement error in the data and can be applied with either a validation subset, on which the true data are also observed (eg, a study audit), or a reliability subset, where a second observation of error prone measurements are available. For each case, we provide conditions under which the proposed method is identifiable and leads to consistent estimates of the regression parameter. When the second measurement on the reliability subset has no error or classical unbiased measurement error, the proposed method is consistent even when the primary outcome and exposures of interest are subject to both systematic and random error. We examine the performance of the method with simulations for a variety of measurement error scenarios and sizes of the reliability subset. We illustrate the method's application using data from the Women's Health Initiative Dietary Modification Trial.

Associations of Number of Daily Eating Occasions with Type 2 Diabetes Risk in the Women's Health Initiative Dietary Modification Trial.

ABSTRACTBackgroundOver 23 million Americans have type 2 diabetes (T2D). Eating habits such as breakfast consumption, time-restricted eating, and limiting daily eating occasions have been explored as behaviors for reducing T2D risk, but prior evidence is inconclusive.ObjectivesOur objectives were to examine associations between number of daily eating occasions and T2D risk in the Women's Health Initiative Dietary Modification Trial (WHI-DM) and whether associations vary by BMI, age, or race/ethnicity.MethodsParticipants were postmenopausal women in the WHI-DM who comprised a 4.6% subsample completing 24-h dietary recalls (24HRs) at years 3 and 6 as part of trial adherence activities (n = 2159). Numbers of eating occasions per day were obtained from the year 3 24HRs, and participants were grouped into approximate tertiles as 1–3 (n = 795), 4 (n = 713), and ≥5 (n = 651) daily eating occasions as the exposure. Incident diabetes was self-reported on semiannual questionnaires as the outcome.ResultsApproximately 15% (15.4%, n = 332) of the WHI-DM 24HR cohort reported incident diabetes at follow-up. Cox proportional hazards regression tested associations of eating occasions with T2D adjusted for neighborhood socioeconomic status, BMI, waist circumference, race/ethnicity, family history of T2D, recreational physical activity, Healthy Eating Index-2005, 24HR energy intake, and WHI-DM arm. Compared with women reporting 1–3 meals/d, those consuming 4 meals/d had a T2D HR = 1.38 (95% CI: 1.03, 1.84) without further increases in risk for ≥5 meals/d. In stratified analyses, associations for 4 meals/d compared with 1–3 meals/d were stronger in women with BMI <30.0 kg/m2 (HR = 1.55; 95% CI: 1.00, 2.39) and women aged ≥60 (HR = 1.61; 95% CI: 1.11, 2.33).ConclusionsFour meals per day compared with 1–3 meals/d was associated with increased risk of T2D in postmenopausal women, but no dose–response effect was observed for additional eating occasions. Further studies are needed to understand eating occasions in relation to T2D risk.

Regression Models and Multivariate Life Tables

Semiparametric, multiplicative-form regression models are specified for marginal single and double failure hazard rates for the regression analysis of multivariate failure time data. Cox-type estimating functions are specified for single and double failure hazard ratio parameter estimation, and corresponding Aalen–Breslow estimators are specified for baseline hazard rates. Generalization to allow classification of failure times into a smaller set of failure types, with failures of the same type having common baseline hazard functions, is also included. Asymptotic distribution theory arises by generalization of the marginal single failure hazard rate estimation results of Lin et al. The Péano series representation for the bivariate survival function in terms of corresponding marginal single and double failure hazard rates leads to novel estimators for pairwise bivariate survival functions and pairwise dependency functions, at specified covariate history. Related asymptotic distribution theory follows from that for the marginal single and double failure hazard rates and the continuity, compact differentiability of the Péano series transformation and bootstrap applicability. Simulation evaluation of the proposed estimation procedures is presented, and an application to multiple clinical outcomes in the Women’s Health Initiative Dietary Modification Trial is provided. Higher dimensional marginal hazard rate regression modeling is briefly mentioned. Supplementary materials for this article are available online.

Eating Pattern Response to a Low-Fat Diet Intervention and Cardiovascular Outcomes in Normotensive Women: The Women's Health Initiative.

ABSTRACTBackgroundWomen without cardiovascular disease (CVD) or hypertension at baseline assigned to intervention in the Women's Health Initiative Dietary Modification (DM) trial experienced 30% lower risk of coronary heart disease (CHD), whereas results in women with hypertension or prior CVD could have been confounded by postrandomization use of statins.ObjectivesIntervention participants reported various self-selected changes to achieve the 20% total fat goals. Reviewed are intervention compared with comparison group HRs for CHD, stroke, and total CVD in relation to specific dietary changes in normotensive participants.MethodsDietary change was assessed by comparing baseline with year 1 FFQ data in women (n = 10,371) without hypertension or CVD at baseline with intake of total fat above the median to minimize biases due to use of the FFQ in trial eligibility screening.ResultsIntervention participants self-reported compensating reduced energy intake from total fat by increasing carbohydrate and protein. Specifically they increased plant protein, with those in the upper quartile (increased total protein by ≥3.3% of energy) having a CHD HR of 0.39 (95% CI: 0.22, 0.71), compared with 0.92 (95% CI: 0.57, 1.48) for those in the lower quartile of change (decreased total protein ≥0.6% of energy), with P-trend of 0.04. CHD HR did not vary significantly with change in percentage energy from carbohydrate, and stroke HR did not vary significantly with any macronutrient changes. Scores reflecting adherence to recommended dietary patterns including the Dietary Approaches to Stop Hypertension Trial and the Healthy Eating Index showed favorable changes in the intervention group.ConclusionsIntervention group total fat reduction replaced with increased carbohydrate and some protein, especially plant-based protein, was related to lower CHD risk in normotensive women without CVD who reported high baseline total fat intake. This trial was registered at clinicaltrials.gov as NCT00000611. Link to the WHI trial protocol: https://www.whi.org/about/SitePages/Dietary%20Trial.aspx.

Dietary Modification and Breast Cancer Mortality: Long-Term Follow-Up of the Women's Health Initiative Randomized Trial.

Observational studies of dietary fat intake and breast cancer have reported inconsistent findings. This topic was addressed in additional analyses of the Women's Health Initiative (WHI) Dietary Modification (DM) clinical trial that evaluated a low-fat dietary pattern influence on breast cancer incidence. In the WHI DM trial, 48,835 postmenopausal women, ages 50-79 years, with no prior breast cancer, and a dietary fat intake of ≥ 32% of energy were randomly assigned at 40 US centers to a usual diet comparison group (60%) or dietary intervention group (40%). The goals were to reduce fat intake to 20% of energy and increase vegetable, fruit, and grain intake. Breast cancers were confirmed after central medical record review and serial National Death Index linkages to enhance mortality findings. During 8.5 years of dietary intervention, breast cancer incidence and deaths as a result of breast cancer were nonsignificantly lower in the intervention group, while deaths after breast cancer were statistically significantly lower both during intervention and through a 16.1-year (median) follow-up. Now, after a long-term, cumulative 19.6-year (median) follow-up, the significant reduction in deaths after breast cancer persists (359 [0.12%] v 652 [0.14%] deaths; hazard ratio [HR], 0.85; 95% CI, 0.74 to 0.96; P = .01), and a statistically significant reduction in deaths as a result of breast cancer (breast cancer followed by death attributed to the breast cancer) emerged (132 [0.037%, annualized risk] v 251 [0.047%] deaths, respectively; HR, 0.79; 95% CI, 0.64 to 0.97; P = .02). Adoption of a low-fat dietary pattern associated with increased vegetable, fruit, and grain intake, demonstrably achievable by many, may reduce the risk of death as a result of breast cancer in postmenopausal women.

Low-fat dietary pattern and global cognitive function: Exploratory analyses of the Women's Health Initiative (WHI) randomized Dietary Modification trial

BackgroundMeta-analyses of observational studies associate adherence to several dietary patterns with cognitive health. However, limited evidence from full scale, randomized controlled trials precludes causal inference regarding dietary effects on cognitive function. MethodsThe Women's Health Initiative (WHI) Dietary Modification (DM) randomized trial, in 48,835 postmenopausal women, included a subset of 1,606 WHI Memory Study (WHIMS) participants >= 65 years old, to assess low-fat dietary pattern influence on global cognitive function, evaluated with annual screening (Modified Mini–Mental State Examinations [3MSE]). Participants were randomized by a computerized, permuted block algorithm, stratified by age group and center, to a dietary intervention (40%) to reduce fat intake to 20% of energy and increase fruit, vegetable and grain intake or usual diet comparison groups (60%). The study outcome was possible cognition impairment (failed cognitive function screening) through the 8.5 year (median) dietary intervention. Those failing screening received a comprehensive, multi-phase cognitive function assessment to classify as: no cognitive impairment, mild cognitive impairment, or probable dementia. Exploratory analyses examined the composite endpoint of death after possible cognitive impairment through 18.7 years (median) follow-up. The WHI trials are registered at ClinicalTrials.gov:NCT00000611. FindingsAmong the 1,606 WHIMS participants, the dietary intervention statistically significantly reduced the incidence of possible cognitive impairment (n = 126; hazard ratio [HR] 0.59 95% confidence interval [CI] 0.38–0. 91, P = 0.01) with HR for dietary influence on subsequent mild cognitive impairment of 0.65 (95% CI 0.35–1.19) and HR of 0.63 (95% CI 0.19–2.10) for probable dementia (PD). Through 18.7 years, deaths from all-causes after possible cognitive impairment were non-significantly lower in the dietary intervention group (0.56% vs 0.77%, HR 0.83 95% CI 0.35 to 2.00, P = 0.16). InterpretationAdoption of a low-fat eating pattern, representing dietary moderation, significantly reduced risk of possible cognitive impairment in postmenopausal women. FundingSeveral Institutes of the US National Institutes of Health.

Low-Fat Dietary Pattern among Postmenopausal Women Influences Long-Term Cancer, Cardiovascular Disease, and Diabetes Outcomes

ABSTRACTBackgroundThe preferred macronutrient dietary composition, and the health consequences of dietary fat reduction specifically, have been debated for decades. Here we provide a comprehensive overview of long-term health outcomes in the Women's Health Initiative Dietary Modification (DM) trial.ObjectiveThe DM trial aimed to examine whether a low-fat dietary pattern would reduce the risk of invasive breast cancer, colorectal cancer, and, secondarily, coronary heart disease (CHD), with various other health outcomes also considered.MethodsThe DM trial is a randomized controlled trial conducted at 40 centers in the US, among 48,835 postmenopausal women aged 50–79 y with baseline intake of ≥32% energy from fat. Participants were randomly assigned to a low-fat dietary pattern intervention group or to a usual-diet comparison group, during 1993–1998. Intervention goals were to reduce fat intake from ∼35% to 20% of total energy, in conjunction with increasing vegetables and fruit to 5 servings/d and grains to 6 servings/d.ResultsOver an 8.5-y (median) intervention period, intervention and comparison group differences included lower fat by 8–10%, and higher carbohydrate by 8–10%, of total energy, in conjunction with higher consumption of vegetables, fruit, and grains. Time-to-outcome analyses did not show significant differences between intervention and comparison groups for invasive breast cancer, colorectal cancer, or CHD, either over the intervention period or over longer-term cumulative follow-up. Additional analyses showed significant intervention group benefits related to breast cancer, CHD, and diabetes, without adverse effects. Over a 19.6-y (median) follow-up period, HRs (95% CIs) were 0.84 (0.74, 0.96) for breast cancer followed by death, and 0.87 (0.77, 0.98) for diabetes requiring insulin.ConclusionsReduction in dietary fat with corresponding increase in vegetables, fruit, and grains led to benefits related to breast cancer, CHD, and diabetes, without adverse effects, among healthy postmenopausal US women.This trial was registered at clinicaltrials.gov as NCT00000611.

Low-fat dietary pattern and breast cancer mortality by metabolic syndrome degree: Secondary analyses of the Women’s Health Initiative (WHI) Dietary Modification randomized trial.

1539 Background: The WHI Diet Modification (DM) trial randomized 48,835 postmenopausal women with no prior breast cancer to a low-fat dietary intervention or comparison group. After 16.1 years follow-up, the intervention was associated with an 18% reduction in risk of death after breast cancer (P =0.01), with greater reduction (29%) in those with waist circumference≥88 cm (J Clin Oncol 2017). To extend these findings, we examined the influence of the dietary intervention on breast cancer mortality in subgroups defined by number of metabolic syndrome (MS) components with 19.6 years median cumulative follow-up. Methods: WHI DM has been previously described. Four MS components were determined at entry: 1) waist circumference≥ 88 cm, 2) high blood pressure or anti-hypertensive use, 3) high cholesterol history and 4) diabetes history, with women categorized as having 0 (n=10,639), 1-2 (n=30,948), or 3-4 (n=4,246) MS components. Forest plots of hazard ratios (HRs) were generated with P-values for interaction between randomized group assignment and number of MS components. Results: Women with 3-4 MS components were more likely to be Black, be obese (BMI ≥30), and have diabetes (all P &lt; 0.001). Breast cancers in women with 3-4 MS components were less likely to be local stage (P = 0.005) or well differentiated (P = 0.03). The magnitude of reduction in deaths from breast cancer in the dietary intervention vs comparison group increased as the number of MS components increased (interaction P = 0.01). Hazard ratios (HR) and 95% confidence intervals (CI) for death from breast cancer for intervention vs comparison groups for women with 0 MS components was 1.09 95% CI, 0.63-1.87, with risk low in both randomization groups (0.028% and 0.026%, respectively); for women with 1-2 MS components, HR 0.80 95% CI 0.62-1.02; and for women with 3-4 MS components, HR 0.31 95% CI, 0.14-0.69, with risk in the intervention group reduced to 0.026%. Conclusions: Adoption of a low-fat dietary pattern had a greater effect on reducing deaths from breast cancer in women with more MS components, suggesting that this is a high risk group more likely to benefit from the dietary intervention. Clinical trial information: NCT00000611.

Low-fat dietary pattern and long-term breast cancer incidence and mortality: The Women’s Health Initiative randomized clinical trial.

520 Background: Observational studies of dietary fat intake and breast cancer have inconsistent findings. To address this issue, the Women’s Health Initiative (WHI) Dietary Modification (DM) clinical trial assessed a low-fat dietary pattern influence on breast cancer incidence and outcome. Methods: The WHI DM trial is a randomized, controlled clinical trial conducted at 40 US centers, where 48,835 postmenopausal women, aged 50-79 years, with no previous breast cancer and dietary fat intake ≥32% of total energy, were randomly assigned, from 1993-1998, to a usual diet comparison group (60%) or dietary intervention group (40%) with goals to reduce fat intake to 20% of energy and increase vegetables, fruit, and grain intake. This study is registered as: NCT00000611. Results: The dietary intervention significantly reduced fat intake; increased fruit, vegetable and grain intake with modest weight loss (3%) (all P&lt; 0.001). During 8.5 years of dietary intervention, there were 8% fewer breast cancers and deaths from breast cancer were somewhat lower in the intervention group but the rates were not significantly different. However, deaths after breast cancer (breast cancer followed by death from any cause) were significantly reduced in the intervention group, both during intervention (hazard ratio [HR] 0·65 95% confidence interval [CI] 0·45-0·95) and through 16.1 year (median) cumulative follow-up. Now, after long- term, cumulative 19.6 year (median) follow-up, with 3,374 incident breast cancers, the significant reduction in deaths after breast cancer continued (with 1,011 deaths, HR 0·85 95% CI 0·74-0·96) and a significant reduction in deaths from breast cancer (breast cancer followed by death attributed to the breast cancer) emerged (with 383 deaths, HR 0·79 95% CI 0·64-0·97). Conclusions: Adoption of a low-fat dietary pattern associated with increased vegetable, fruit, and grain intake, demonstrably achievable by many, significantly reduced the risk of death from breast cancer in postmenopausal women. To our review, these findings provide the first randomized clinical trial evidence that a dietary change can reduce a postmenopausal woman’s risk of dying from breast cancer. Clinical trial information: NCT00000611.

Is There a Spillover Effect of Targeted Dietary Change on Untargeted Health Behaviors? Evidence From a Dietary Modification Trial.

Background. The gateway behavior hypothesis posits that change in a health behavior targeted for modification may promote positive changes in other untargeted health behaviors; however, previous studies have shown inconsistent results. Aims. To examine the patterns and predictors of change in untargeted health behaviors in a large health behavior change trial. Method. Using repeated-measures latent class analysis, this study explored patterns of change in untargeted physical activity, alcohol consumption, and smoking behavior during the first year of the Women's Health Initiative dietary modification trial that targeted total fat reduction to 20% kcal and targeted increased fruit and vegetable intake. Participants were healthy postmenopausal women who were randomly assigned to either the low-fat dietary change intervention (n = 8,193) or a control (n = 12,187) arm. Results. Although there were increases in untargeted physical activity and decreases in alcohol consumption and smoking in the first year, these changes were not consistently associated with study arm. Moreover, although the results of the repeated-measures latent class analysis identified three unique subgroups of participants with similar patterns of untargeted health behaviors, none of the subgroups showed substantial change in the probability of engagement in any of the behaviors over 1 year, and the study arms had nearly identical latent class solutions. Discussion and Conclusion. These findings suggest that the dietary intervention did not act as a gateway behavior for change in the untargeted behaviors and that researchers interested in changing multiple health behaviors may need to deliberately target additional behaviors.