Aerobics Center Longitudinal Study Research Articles

A cross-sectional study of cardiorespiratory fitness and gallbladder disease

PurposeTo determine the association of different levels of cardiorespiratory fitness (CRF), an objective indicator of habitual physical activity, with gallbladder disease. MethodsIn the Aerobics Center Longitudinal Study (ACLS) database, 41,528 men and 13,206 women aged 20–90 years, with body mass index of 18.5 or more and without history of cardiovascular disease and cancer, received a preventive examination at the Cooper Clinic in Dallas, Texas, between 1970 and 2003. CRF was quantified as maximal metabolic equivalents and classified as low, moderate, and high based on traditional ACLS cut points. Gallbladder disease was defined as physician-diagnosed gallbladder disease. ResultsWhen compared with low CRF, adjusted odds ratios and 95% confidence intervals for gallbladder disease for those with moderate and high CRF were 0.74 (0.55–0.99) and 0.59 (0.42–0.82), respectively when adjusted for all the potential confounders. Each one metabolic equivalent increment of CRF was associated with 10% lower odds of gallbladder disease in all participants (P for trend <.001), 13% lower in women (P for trend <.001), and 8% lower in men (P for trend = .08). The association was consistent across age, history of diabetes mellitus, and physical inactivity subgroups. ConclusionsCRF is inversely related to the prevalence of gallbladder disease among relatively healthy men and women in the ACLS cohort.

Cardiovascular disease risk in obese adults assessed using established values for cardiorespiratory fitness.

The present study was designed to assess the risk of cardiovascular disease as determined by cardiorespiratory fitness (CRF) in a large sample of inactive, obese adults. Cardiovascular disease risk was determined using published age- and sex-adjusted values for low, moderate, and high CRF from the Aerobics Center Longitudinal Study (ACLS). Contrary to expectations, ACLS-CRF classifications identified approximately 60% of our inactive, obese adults as having moderate or high CRF and hence, low cardiovascular disease risk.

Cardiorespiratory Fitness and Risk of Sudden Cardiac Death in Men and Women in the United States: A Prospective Evaluation From the Aerobics Center Longitudinal Study

ObjectivesTo examine the relation between cardiorespiratory fitness (CRF) and sudden cardiac death (SCD) in a large US adult population and to study the effects of hypertension, obesity, and health status on the relation of CRF with SCD. Patients and MethodsA total of 55,456 individuals (mean age, 44.2 years; 13,507 women) from the Aerobics Center Longitudinal Study, a prospective observational investigation (from January 2, 1974, through December 31, 2002), were included. Cardiorespiratory fitness was assessed by a maximal treadmill test, and baseline assessment included an extensive set of measurements. ResultsThere were 109 SCDs. An inverse risk of SCD was found across incremental CRF levels after adjusting for potential confounders. Participants with moderate and high CRF levels had 44% (hazard ratio, 0.56; 95% CI, 0.35-0.90) and 48% (hazard ratio, 0.52; 95% CI, 0.30-0.92) significantly lower risk of SCD, respectively, than did those with low CRF levels (P<.001). The risk of SCD decreased by 14% (hazard ratio, 0.86; 95% CI, 0.77-0.96) per 1-metabolic equivalent increase in the fully adjusted model. Hypertensive, overweight, or unhealthy individuals with moderate to high CRF levels had lower risks of SCD (ranging from 58% to 72% of lower risk) than did those with the same medical conditions and low CRF levels. ConclusionThe risk of SCD in US men and women could be partially reduced by ensuring moderate to high levels of CRF independently of other risk factors and especially in those who are hypertensive, overweight, or unhealthy.

Cardiorespiratory Fitness within an Obesity Risk Classification Model Identifies Men at Increased Risk of Mortality

Guidelines for identification of obesity-related risk stratify disease risk using specific combinations of body mass index (BMI) and waist circumference (WC). Whether the addition of cardiorespiratory fitness (CRF), an independent predictor of disease risk, provides better risk prediction of all-cause mortality within current BMI and WC categories is unknown. PURPOSE: To determine whether the addition of CRF improves prediction of all-cause mortality risk classified by established categorization of BMI and WC. METHODS: Prospective observational data from the Aerobics Center Longitudinal Study (ACLS). A total of 31,267 men (mean (SD) age 43.9 (9.4) years completed a baseline medical examination during 1974-2002. Participants were grouped according to the following BMI- and WC-specific threshold combinations: Normal BMI of 18.5-24.9 kg/m2, WC threshold of 90 cm; overweight BMI of 25.0-29.9 kg/m2, WC threshold of 100 cm, and obese BMI of 30.0-34.9 kg/m2, WC threshold of 110 cm. Participants were classified by CRF as unfit or fit. Unfit was defined as the lowest fifth of the age-specified distribution of maximal exercise test time on treadmill among the entire ACLS population. The main outcome measure was all-cause mortality. RESULTS: 1,399 deaths occurred over an average length of follow-up of 14.1 ± 7.4 years, for a total of 439, 991 person-years of observation. Males who were unfit and normal BMI with WC<90 cm and ≥90 cm had 95% (1.95, 1.34-2.83) [Hazard ratio, 95% confidence interval] and 163% (2.63, 1.58-4.40) higher mortality risk than males who were fit, respectively (p<.05). Males who were unfit and overweight had 41% (1.41, 1.04-1.90) higher mortality risk with a WC <100 cm (p<.05), but were at no greater risk (1.30, 0.92-1.84) if their WC was ≥100 cm (p=.14). Males who were unfit and obese were not at increased mortality risk (1.37, 0.90-2.09) with a WC <110 cm (p=.14), but were at 111% (2.11, 1.31-3.42) increased risk with a WC ≥110 cm (p<.05). CONCLUSIONS: For most of the BMI and WC categories, inclusion of CRF allowed for improved identification of males at increased mortality risk.

Baseline Physical Activity Moderates the Effect of Yoga on Pain in Cancer Survivors

PURPOSE: Greater than 50% of cancer patients experience pain, including neuropathic pain, arthralgia, and generalized pain, from cancer and its treatments. Pain often persists for years after treatment, significantly impairing recovery, physical function, and quality of life. We previously conducted a phase III randomized controlled trial (RCT) in cancer survivors showing that yoga ameliorates insomnia, fatigue, and impaired quality of life. To date, no phase III RCTs have examined both the influence of yoga on generalized pain and moderators to help understand for whom and when yoga works best. Here, we assessed 1) the effectiveness of yoga for treating pain and 2) factors that may moderate the influence of yoga on pain. METHODS: Cancer survivors (2-24 months post treatment, 96% female, 77% breast cancer) were randomized to either usual care (N=157) or Yoga for Cancer Survivors (YOCAS©®; N=167). YOCAS consists of breathing exercises, postures, and meditation in two 75-min sessions/wk for four wks. We assessed pain (0-10) using a Symptom Inventory both pre- and post-intervention. Potential moderators included: 1) Exercise Stage of Change (ESC; ESC question), 2) frequency of vigorous physical activity (Aerobics Center Longitudinal Study sweat question), 3) cancer stage (I-IV), 4) cancer treatment (surgery, chemotherapy, radiation, hormone therapy), and 5) age. RESULTS: Yoga reduced pain (change score; CS=-0.40, SE=0.18, p<0.01) whereas usual care did not (CS=-0.06, SE=0.18, p=0.38). Moderation analyses (p<0.01) demonstrated that 1) for survivors with frequent vigorous physical activity (>9/wk), pain decreased in yoga but increased in usual care; 2) for survivors with infrequent vigorous physical activity (<3/wk), pain did not change in either group. There was no evidence of moderation via ESC, age, cancer stage or treatment (ps > 0.11). CONCLUSION: Results suggest that yoga reduces pain in cancer survivors. Survivors with frequent vigorous physical activity (>9/wk) experiencing pain showed reduced pain by changing activity mode to yoga. In contrast, usual care survivors showed increased pain, and survivors with infrequent vigorous physical activity (<3/wk) showed no change in pain. Clinicians should consider yoga for survivors reporting pain. Funded by NCI via NCORP, R25, and K grants.

Addition of Cardiorespiratory Fitness Within an Obesity Risk Classification Model Identifies Men at Increased Risk of All-Cause Mortality

ObjectiveGuidelines for identification of obesity-related risk which stratify disease risk using specific combinations of body mass index and waist circumference. Whether the addition of cardiorespiratory fitness, an independent predictor of disease risk, provides better risk prediction of all-cause mortality within current body mass index and waist circumference categories is unknown. The study objective was to determine whether the addition of cardiorespiratory fitness improves prediction of all-cause mortality risk classified by the combination of body mass index and waist circumference. MethodsWe performed a prospective observational study using data from the Aerobics Center Longitudinal Study. A total of 31,267 men (mean age, 43.9 years; standard deviation, 9.4 years) who completed a baseline medical examination between 1974 and 2002 were included. The main outcome measure was all-cause mortality. Participants were grouped using body mass index– and waist circumference–specific threshold combinations: normal body mass index: 18.5 to 24.9 kg/m2, waist circumference threshold of 90 cm; overweight body mass index: 25.0 to 29.9 kg/m2, waist circumference threshold of 100 cm, and obese body mass index: 30.0 to 34.9 kg/m2, waist circumference threshold of 110 cm. Participants were classified using cardiorespiratory fitness as unfit or fit, where unfit was the lowest fifth of the age-specified distribution of maximal exercise test time on the treadmill among the entire Aerobics Center Longitudinal Study population. ResultsA total of 1399 deaths occurred over a follow-up of 14.1 ± 7.4 years, for a total of 439,991 person-years of observation. Men who were unfit and had normal body mass index with waist circumference <90 cm and ≥90 cm had 95% (hazard ratio [HR], 1.95; 95% confidence interval [CI], 1.34-2.83) and 163% (HR, 2.63; 95% CI, 1.58-4.40) higher mortality risk than men who were fit, respectively (P <.05). Men who were unfit and overweight had 41% (HR, 1.41; 95% CI, 1.04-1.90) higher mortality risk with a waist circumference <100 cm (P <.05), but were at no greater risk (HR, 1.30; 95% CI, 0.92-1.84) if their waist circumference was ≥100 cm (P = .14). Men who were unfit and obese were not at increased mortality risk (HR, 1.37; 95% CI, 0.90-2.09) with a waist circumference <110 cm (P = .14), but were at 111% (HR, 2.11; 95% CI, 1.31-3.42) increased risk with a waist circumference ≥110 cm (P <.05). ConclusionsFor most of the body mass index and waist circumference categories, inclusion of cardiorespiratory fitness allowed for improved identification of men at increased mortality risk.

Association of Cardiorespiratory Fitness With Coronary Heart Disease in Asymptomatic Men

ObjectiveTo examine the association of cardiorespiratory fitness (CRF) with risk of coronary heart disease (CHD) while controlling for an individual's Framingham Risk Score (FRS)–predicted CHD risk. Patients and MethodsThe study included 29,854 men from the Aerobics Center Longitudinal Study, who received a baseline examination from January 1, 1979, to December 31, 2002. Coronary heart disease events included self-reported myocardial infarction or revascularization or CHD death. Multivariable survival analysis investigated the association between CRF, FRS, and CHD. Cardiorespiratory fitness was analyzed as both a continuous and a categorical variable. The population was stratified by “low” and “moderate or high” risk of CHD to test for differences in the FRS stratified by CRF. ResultsCompared with men without incident CHD, men with incident CHD were older (mean age, 51.6 years vs 44.6 years), had lower average maximally achieved fitness (10.9 metabolic equivalent of tasks vs 12.0 metabolic equivalent of tasks [METs]), and were more likely to have moderate or high 10-year CHD risk (P<.001). Cardiorespiratory fitness, defined as maximal METs, exhibited a 20% lower risk of CHD (hazard ratio, 0.80; 95% CI, 0.77-0.83) for each 1-unit MET increase. Among men in the low CRF strata, individuals with moderate or high 10-year CHD risk, according to the FRS, had a higher CHD risk (hazard ratio, 6.55; 95% CI, 3.64-11.82) than men with low CHD risk according to the FRS. ConclusionClinicians should promote physical activity to improve CRF so as to reduce CHD risk, even to patients with otherwise low CHD risk.

Influence of the Source of Social Support and Size of Social Network on All-Cause Mortality

ObjectiveTo examine associations between relative, friend, and partner support, as well as size and source of weekly social network, and mortality risk in the Aerobics Center Longitudinal Study. Patients and MethodsIn a mail-back survey completed between January 1, 1990, and December 31, 1990, adult participants in the Aerobics Center Longitudinal Study (N=12,709) answered questions on whether they received social support from relatives, friends, and spouse/partner (yes or no for each) and on the number of friends and relatives they had contact with at least once per week. Participants were followed until December 31, 2003, or until the date of death. Cox proportional hazards regression analyses evaluated the strength of the associations, controlling for covariates. ResultsParticipants (3220 [25%] women) averaged 53.0±11.3 years of age at baseline. During a median follow-up of 13.5 years, 1139 deaths occurred. Receiving social support from relatives reduced mortality risk by 19% (hazard ratio [HR], 0.81; 95% CI, 0.68-0.95). Receiving spousal/partner support also reduced mortality risk by 19% (HR, 0.81; 95% CI, 0.66-0.99). Receiving social support from friends was not associated with mortality risk (HR, 0.90; 95% CI, 0.75-1.09); however, participants reporting social contact with 6 or 7 friends on a weekly basis had a 24% lower mortality risk than did those in contact with 0 or 1 friend (HR, 0.76; 95% CI, 0.58-0.98). Contact with 2 to 5 or 8 or more friends was not associated with mortality risk, nor was the number of weekly contacts with relatives. ConclusionReceiving social support from one’s spouse/partner and relatives and maintaining weekly social interaction with 6 to 7 friends reduced mortality risk. Such data may inform interventions to improve long-term survival.

The Effect of Cardiorespiratory Fitness on Age-Related Lipids and Lipoproteins

BackgroundEvidence on the effect of cardiorespiratory fitness (CRF) on age-related longitudinal changes of lipids and lipoproteins is scarce. ObjectivesThis study sought to assess the longitudinal aging trajectory of lipids and lipoproteins for the life course in adults and to determine whether CRF modifies the age-associated trajectory of lipids and lipoproteins. MethodsData came from 11,418 men, 20 to 90 years of age, without known high cholesterol, high triglycerides, cardiovascular disease, and cancer at baseline and during follow-up from the Aerobics Center Longitudinal Study. There were 43,821 observations spanning 2 to 25 health examinations (mean 3.5 examinations) between 1970 and 2006. CRF was quantified by a maximal treadmill exercise test. Marginal models using generalized estimating equations were applied. ResultsTotal cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), triglycerides, and non–high-density lipoprotein cholesterol (non–HDL-C) presented similar inverted U-shaped quadratic trajectories with aging: gradual increases were noted until age mid-40s to early 50s, with subsequent declines (all p < 0.0001). Compared with men with higher CRF, those with lower CRF developed abnormal values earlier in life: TC (≥200 mg/dl), LDL-C (≥130 mg/dl), non–HDL-C (≥160 mg/dl), and triglycerides/HDL-C ratio (≥3.0). Notably, abnormal values for TC and LDL-C in men with low CRF were observed around 15 years earlier than in those with high CRF. After adjusting for time-varying covariates, a significant interaction was found between age and CRF in each trajectory, indicating that CRF was more strongly associated with the aging trajectories of lipids and lipoproteins in young to middle-age men than in older men. ConclusionsOur investigation reveals a differential trajectory of lipids and lipoproteins with aging according to CRF in healthy men and suggests that promoting increased CRF levels may help delay the development of dyslipidemia.

Longitudinal Patterns Of Cardiorespiratory Fitness Can Predict The Development Of Hypertension Among Men And Women

PURPOSE: It is well established that cardiorespiratory fitness (CRF) is a significant predictor of incident hypertension (HTN). However, limited literature exists on the effect of change in CRF on HTN. Most of the studies have linked either baseline CRF, or change between baseline and one follow-up CRF, to HTN. These analyses have largely ignored the longitudinal pattern of CRF that considers all the follow-up measures. METHODS: 14,594 participants (17% women) from the Aerobics Center Longitudinal Study (ACLS), aged from 20 to 82 years and free of baseline HTN, received at least two preventive medical examinations (range 2-29) at the Cooper Clinic in Dallas, TX, during 1971 - 2003. Participants were classified into consistent (within 1% of yearly change during all visits), increasing (a linear upward trend with at least one visit ≥1% of yearly change), decreasing (a linear downward trend with at least one visit ≥1% of yearly change), bell-shape (bell-curve with highest yearly change ≥1% ), u-shape (u-curve with highest yearly change ≥1%), and inconsistent (no clear pattern) six groups based on all the observed CRF values (in METs) during maximal treadmill tests. Logistic regression was used to compute odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: During follow-up (±6 years), 4,022 participants developed HTN (407 in women). After controlling for baseline age, BMI, smoking, alcohol intake, self-reported physical activity, diabetes, hypercholesterolemia, and family history of HTN, ORs (95% CIs) for HTN were: 1.00 for decreasing group (referent), 0.41 (0.36-0.46) for increasing, 0.57 (0.50-0.64) for consistent, 0.72 (0.60-0.85) for bell-shape, 1.29 (1.10-1.51) for u-shape, and 1.04 (0.92-1.19) for inconsistent group in men; and 0.54 (0.39-0.76) for increasing, 0.78 (0.56-1.09) for consistent, 1.24 (0.80-1.93) for bell-shape, 1.50 (0.96-2.34) for u-shape, and 1.56 (1.08-2.25) for inconsistent group in women. CONCLUSIONS: An increasing pattern of CRF provides the lowest risk of HTN in both genders; consistent or bell-shaped pattern also had beneficial effects in men. A u-shaped pattern in men or an inconsistent pattern in women is related to a higher risk of HTN. Identifying longitudinal patterns of CRF associated with incident HTN has potentially important public health and clinical implications.

Decline in cardiorespiratory fitness and odds of incident sleep complaints.

To examine longitudinal change in cardiorespiratory fitness and odds of incident sleep problems. A cohort of 7368 men and 1155 women, age 20-85 yr, was recruited from the Aerobics Center Longitudinal Study. The cohort did not complain of sleep problems, depression, or anxiety at their first clinic visit. Cardiorespiratory fitness assessed at four clinic visits between 1971 and 2006, each separated by an average of 2-3 yr, was used as a proxy measure of cumulative physical activity exposure. Sleep complaints were made to a physician during follow-up. Across visits, there were 784 incident cases of sleep complaints in men and 207 cases in women. After adjusting for age, time between visits, body mass index, smoking, alcohol use, chronic medical conditions, complaints of depression or anxiety at each visit, and fitness at visit 1, each minute of decline in treadmill endurance (i.e., a decline in cardiorespiratory fitness of approximately 0.5 MET) between the ages of 51 and 56 yr increased the odds of incident sleep complaints by 1.7% (range = 1.0%-2.4%) in men and by 1.3% (range = 0.0%-2.8%) in women. Odds were ∼8% higher per minute decline in people with sleep complaints at visits 2 and 3. The results indicate that maintenance of cardiorespiratory fitness during middle age, when decline in fitness typically accelerates and risk of sleep problems is elevated, helps protect against the onset of sleep complaints made to a physician.

Improved Cardiovascular Health Outcomes with Health Club Membership

Many individuals purchase health club memberships (hereafter membership) in order to improve their fitness and health. However, there is little evidence showing the effectiveness of a membership on improving fitness and health. PURPOSE: We examined the associations between a membership and cardiovascular health outcomes: peripheral blood pressure (BP), resting heart rate (RHR), and cardiorespiratory fitness (CRF). METHODS: We conducted a cross-sectional study of 413 adults (mean age: 48, range: 30-64). Approximately half had health club memberships (n = 209) and half did not (n = 204). Participants completed measurements of resting BP, RHR, and a self-report questionnaire about health club and lifestyle physical activity (PA) over the past month. We used a population based CRF estimation equation developed and validated in the Aerobics Center Longitudinal Study. RESULTS: The average values (SD) of resting systolic/diastolic BP, RHR, and CRF were 115/76 (14/9) mmHg, 67(10) bpm, and 38 (7) mL/kg/min for those with a membership and 116/77 (17/10) mmHg, 71(10) bpm, and 36(7) mL/kg/min for those without a membership, respectively. In multivariable linear regression analyses, having a membership was significantly (p < 0.01) associated with a lower RHR (ß = -4.60, 95% CI -6.55, -2.65) and a higher CRF (ß = 1.57, 95% CI 1.14, 1.99) after adjusting for age, sex, body mass index, health status, and smoking status. Even after further adjustment for PA and sedentary time, RHR and CRF remained significant (p < 0.01). Although not significant, participants with a membership also had lower systolic/diastolic BP (ß = -0.88, 95% CI -3.41, 1.65, p = 0.49 / ß = -1.00, 95% CI -2.67, 0.67, p=0.24). In the combined logistic regression analyses, there appears to be stronger and more favorable associations with cardiovascular risk factors in individuals with a membership plus meeting the aerobic PA guidelines or having a lower sedentary time. In addition, membership duration was likely to be associated with more favorable cardiovascular health outcomes. CONCLUSION: Having a health club membership was associated with improved cardiovascular disease risk factors and was stronger in those individuals also meeting the aerobic PA guidelines or having a lower sedentary time. Supported by Iowa State University College of Human Sciences seed grant.

Abstract MP05: Leisure-Time Running and Incident Type 2 Diabetes

Introduction: There is still little evidence on the dose-response relation between leisure-time running and incident type 2 diabetes (T2D). Hypothesis: We examined the hypothesis that running reduces the risk of developing T2D. Methods: Participants were 19,347 adults aged 18 to 100 years (mean age, 44) who received an extensive preventive medical examination during 1974-2006 in the Aerobics Center Longitudinal Study. Participants were free of cardiovascular disease, cancer, and T2D at baseline. Running and other physical activities were assessed on the medical history questionnaire by self-reported leisure-time activities during the past 3 months. We defined T2D as fasting glucose ≥126 mg/dl, insulin use, or physician-diagnosis during follow-up medical examinations. Cox regression was used to quantify the association between running and T2D after adjusting for baseline age, sex, examination year, body mass index, smoking status, heavy alcohol drinking, abnormal electrocardiogram, hypertension, hypercholesterolemia, and levels of other physical activities. Results: During an average follow-up of 6.5 years, 1,015 adults developed T2D. Approximately 30% of adults participated in leisure-time running. Runners had a 29% lower risk of developing T2D compared with non-runners. The hazard ratios (95% confidence intervals) of T2D were 0.97 (0.74-1.27), 0.66 (0.49-0.89), 0.62 (0.45-0.85), 0.78 (0.58-1.03), and 0.57 (0.42-0.79) across quintiles (Q) of running time (minutes/week); 0.99 (0.76-1.30), 0.60 (0.44-0.82), 0.72 (0.55-0.94), 0.65 (0.47-0.90), and 0.63 (0.47-0.86) across Q of running distance (miles/week); 1.08 (0.83-1.40), 0.67 (0.50-0.90), 0.70 (0.53-0.93), 0.61 (0.45-0.83), and 0.53 (0.36-0.76) across Q of running frequency (times/week); 0.95 (0.73-1.24), 0.70 (0.52-0.94), 0.62 (0.45-0.84), 0.73 (0.55-0.97), and 0.58 (0.42-0.80) across Q of total amount of running (MET-minutes/week); and 0.95 (0.71-1.28), 0.76 (0.59-0.99), 0.59 (0.42-0.83), 0.66 (0.51-0.85), and 0.62 (0.43-0.90) across Q of running speed (mph), respectively, compared with no running after adjusting for confounders including levels of other physical activities. Conclusions: Participating in leisure-time running is associated with markedly lower risk of developing T2D in adults. Except for those in the very lowest Q for running doses, even relatively low running doses (starting with Q 2) were associated with marked reductions in T2D risk over time, supporting the prescription of running to reduce T2D.

A prospective study of fitness, fatness, and depressive symptoms.

Being overweight or obese might be a risk factor for developing depression. It is also possible that low cardiorespiratory fitness, rather than overweight or obesity, is the better predictor of depressive symptom onset. Adults in the Aerobics Center Longitudinal Study (Dallas, Texas) underwent fitness and fatness assessments between 1979 and 1998 and later completed a questionnaire about depressive symptoms in 1990, 1995, or 1999. Separate logistic regression models were used to test the associations between 3 fatness measures (body mass index, waist circumference, and percentage of body fat) and the onset of depressive symptoms. Analyses were repeated using fitness as the predictor variable. Additional analyses were performed to study the joint association of fatness and fitness with the onset of depressive symptoms. After controlling for fitness, no measure of fatness was associated with the onset of depressive symptoms. In joint analyses, low fitness was more strongly associated with the onset of elevated depressive symptoms than was fatness, regardless of the measure of fatness used. Overall, results from the present study suggest that low fitness is more strongly associated with the onset of elevated depressive symptoms than is fatness. To reduce the risk of developing depression, individuals should be encouraged to improve their fitness regardless of body fatness.

Becofsky et al. Respond to "Misclassifying Fitness and Depression"

We appreciate Dr. Mukamal's thoughtful commentary (1) on our paper (2). We are in agreement with Dr. Mukamal on a number of points, but wish to re-affirm and clarify our stance on others. In his commentary, Dr. Mukamal says, “To some degree, this [fit versus fat] debate is poorly suited to epidemiologic inquiry” (1, p. 321). He stresses that it is difficult to ascertain repeated, quality measurements of fitness in epidemiologic studies. This point speaks to the importance of our paper and others published on the topic using data from the Aerobics Center Longitudinal Study cohort (3–6), from which “reasonable measures of both fitness and fatness” are available, as Dr. Mukamal notes (1, p. 322). In speaking of fitness and fatness, Dr. Mukamal notes that “their strong interrelationships raise legitimate questions about the clinical utility of trying to parse their separate roles too finely” (1, p. 321). Perhaps in terms of clinical utility, his statement is sound; if obese patients begin exercising and lose weight, it is unnecessary to pick apart which physiological adaptations are responsible for the numerous downstream health benefits. From a messaging perspective, though, we believe it is critical to understand which factor, low fitness or high fatness, is a stronger predictor of negative health outcomes. As many persons struggling with weight management can attest, being active does not always translate to weight loss. Alternatively, underactive persons in the “normal” range of body mass index should not be made to believe that “skinny” means “healthy” because of a cultural and clinical emphasis on weight loss. If fitness is a better predictor of negative health outcomes than is fatness (as has been shown repeatedly (7)), clinicians and public health professionals alike have a responsibility to emphasize that leading an active lifestyle is more important than having a body mass index in the “normal” range. Dr. Mukamal's critique of our study focuses on the possibility that responses to 2 items from the Center for Epidemiologic Studies Depression Scale (“inability to ‘get going’” and “the feeling that everything is an effort”) might have been influenced by lack of fitness. We explicitly acknowledged this possibility in the limitations section of our paper. We also would like to stress that fatigue and loss of energy are core symptoms of depression and that it would be inappropriate to claim that “unfit” participants endorsing these items are doing so because of their fitness level rather than their mental health status. Further, these questions could be interpreted by participants as referring to a lack of motivation or concentration, in other words, a psychological “inability to get going” and “feeling that everything is an effort” rather than physical fatigue. As Dr. Mukamal points out, depression is complex and multidimensional. It is also prevalent and debilitating. We cannot shy away from studying modifiable risk factors, such as cardiorespiratory fitness and fatness, simply because they might overlap with a few of the many possible symptoms of depression. Dr. Mukamal mentions that, when possible, subscales of larger instruments might be helpful in studying relationships among specific aspects of complex diseases. We agree but recognize that many epidemiologists interested in the fitness-depression relationship might not have this option. In these cases, the overlap between the exposure (fitness) and the composite outcome variable should always be acknowledged and considered (as in our article), but it should not be viewed as damning. These variables are clearly separate entities, and understanding their relationship has important implications for public health.

Associations Between Television Watching and Car Riding Behaviors and Development of Depressive Symptoms: A Prospective Study

ObjectiveTo examine the longitudinal association between sedentary behaviors and risk of development of depressive symptoms. Patients and MethodsThe study population consisted of 4802 participants in the Aerobics Center Longitudinal Study (1012 women and 3790 men) aged 18 to 80 years who did not report depressive moods when they completed a health survey during 1982 in which they reported their time spent watching television (TV) and riding in a car each week. All participants completed a follow-up health survey when they responded to the 10-item Center for Epidemiologic Studies Depression Scale. Those who scored 8 or more on the Center for Epidemiologic Studies Depression Scale were considered to have depressive symptoms. ResultsAmong the 4802 participants, 568 reported depressive symptoms during a mean follow-up of 9.3 years. After multivariate adjustment including moderate- and vigorous-intensity physical activity, time riding in a car, time watching TV, and combined time spent in the 2 sedentary behaviors were positively associated with depressive symptoms (each P<.05 for trend). Individuals who reported 9 h/wk or more riding in a car, more than 10 h/wk watching TV, or 19 h/wk or more of combined sedentary behavior had 28%, 52%, and 74% greater risk of development of depressive symptoms than those who reported less than 5 h/wk, less than 5 h/wk, or less than 12 h/wk, respectively, after adjusting for baseline covariates and moderate- and vigorous-intensity physical activity. The positive association between time riding in a car or time watching TV and depressive symptoms was only observed among individuals who did not meet the current physical activity guidelines. ConclusionMore time reported in these 2 sedentary behaviors was positively associated with depressive symptoms. However, the direct associations between time spent in car riding and TV viewing and depressive symptoms were only significant among those who did not meet the current physical activity recommendations.

Parental History of Premature Cardiovascular Disease, Estimated GFR, and Rate of Estimated GFR Decline: Results From the Aerobics Center Longitudinal Study

Despite cardiovascular disease (CVD) and chronic kidney disease sharing similar causes and interplay, it is unknown if a broader relationship between these diseases exists across generations. We investigated the association between parental CVD history and estimated glomerular filtration rate (eGFR) in the community. Cross-sectional and longitudinal analyses. 13,241 community-based adults with serum creatinine measurement and follow-up visits (from 1-8 visits ~2 years apart) from the Aerobics Center Longitudinal Study. Premature parental CVD history (before age 50 years). eGFR, decreased eGFR (<60 mL/min/1.73 m(2)), and rate of eGFR decline. Information for parental history was collected by protocol-standardized questionnaires. eGFR was assessed with serum creatinine. 3,339 (25.2%) participants reported a history of parental CVD. Individuals with parental CVD had significantly lower eGFRs compared with those without parental CVD (69.4 ± 12.9 vs 74.8 ± 14.2 mL/min/1.73 m(2); P<0.001). After multivariable adjustment, parental CVD was associated independently with higher odds of having decreased eGFR (adjusted OR, 1.68; 95% CI, 1.52-1.86). Random-coefficient models showed that individuals with parental CVD had a faster decline in eGFR compared with those without parental CVD (sex- and ethnicity-adjusted annual change of -0.47 vs -0.41 mL/min/1.73 m(2); P=0.06). ~70% of participants did not attend a second examination. Parental history of CVD was associated with lower baseline eGFR, higher odds of decreased eGFR, and a nominally faster rate of eGFR decline in the offspring. Such findings may imply previously unrecognized cross-generational links between both diseases and be of support in community screening programs.

The Effects of Sedentary Behavior on Metabolic Syndrome Independent of Physical Activity and Cardiorespiratory Fitness

Background: To date, no longitudinal studies have examined the influence of sedentary behavior on metabolic syndrome development while accounting for cardiorespiratory fitness. Purpose and Methods: This prospective study examined the relationship between sedentary behavior and incident metabolic syndrome while considering the effects of physical activity and cardiorespiratory fitness on the association among 930 men enrolled in the Aerobics Center Longitudinal Study. Results: A total of 124 men developed metabolic syndrome during 8974 person-years of exposure. After adjusting for covariates, men with middle and high sedentary behavior had 65% and 76% higher risks of developing metabolic syndrome, respectively, than men with low sedentary behavior (linear trend P = .011). This association remained significant after additional adjustment for activity status and cardiorespiratory fitness. Cardiorespiratory fitness and physical activity were also inversely associated with metabolic syndrome, even after adjustment for sedentary behavior. Conclusions: The findings highlight the importance of reducing sedentary behavior, increasing physical activity, and improving cardiorespiratory fitness for preventing metabolic syndrome.

Metabolic syndrome and discrepancy between actual and self-identified good weight: Aerobics Center Longitudinal Study

This study examined whether the discrepancy between measured and self-identified good weight (weight discrepancy) predicts metabolic syndrome (MetSyn). This study included 6,413 participants enrolled in the Aerobics Center Longitudinal Study (mean follow-up: 4.8±3.8 years). Weight discrepancy was defined as measured weight minus self-identified good weight. MetSyn was defined using standard definitions. Hazard ratios (HRs) and 95% confidence intervals (95% CIs) for incident MetSyn, by weight discrepancy category, were estimated using Cox proportional hazards regression. The multivariable-adjusted HR for MetSyn was 3.48 (95% CI=2.48–4.86) for those who maintained higher weight discrepancy over time compared to individuals with lower weight discrepancy. Additional adjustment for body mass index did not change this interpretation (HR=3.44; 95% CI=2.46–4.82). Weight discrepancy may be a useful screening characteristic and target for future interventions to further reduce the risk of chronic weight-related disorders, included MetSyn.

Secular Change in Cardiorespiratory Fitness and Body Composition of Women: The Aerobics Center Longitudinal Study

ObjectiveTo investigate secular change of cardiorespiratory fitness (CRF) and body composition during 35 years in a large sample of women enrolled in the Aerobics Center Longitudinal Study. Patients and MethodsA cross-sectional analysis of baseline fitness data collected during preventive medical examination of 13,037 women aged 20 to 64 years evaluated at the Cooper Clinic in Dallas, Texas, from January 1, 1970, through December 30, 2004, who underwent a body composition assessment and a maximal treadmill exercise test. Women were stratified by examination year (5 years for each group) and age. Analysis of covariance was used to ascertain secular change of CRF and body composition. ResultsAdjusted CRF levels, as indicated by maximal metabolic equivalent or relative maximum oxygen consumption, among women in the cohort increased significantly during a 35-year period for both age groups (P<.001). The greatest change occurred during the 1970s to 1980s, with a small decrease in 2000 through 2004 in both age groups. Adjusted body mass index increased 9.05% during the past 35 years (P<.001), but adjusted percentage of body fat was significantly higher in 1980 through 1984 than in the other groups (P<.001). ConclusionsIn a large cohort of women, the mean CRF has improved during the past 35 years, with a slight decrease in 2000 through 2004. From 1980 through 2004, the increase in body weight was mainly attributable to the increase in fat-free mass.