Effects Of Lifestyle Risk Factors Research Articles

Association of risk factors for high blood pressure across 46 low- and middle-income countries: A multi-country cross-sectional analysis.

Despite acknowledging the influence of various lifestyle and metabolic risk factors on hypertension, it remains uncertain to identify the primary contributors and differentiate which modifiable risk factors mediate the causal effects of hypertension. We aimed to examine the hierarchical association of eight prominent lifestyle and metabolic risk factors, along with demographic variables, with hypertension in adults and to explore the mediating effects of modifiable metabolic risk factors on hypertension. A cross-sectional study was conducted in 46 low- and middle-income countries using the World Health Organization (WHO) STEPwise approach to noncommunicable disease risk factor surveillance from 2002 to 2020. In a sample of 179 535 non-pregnant adults, we assessed the weighted population-attributable risk percentages (PAR%) for hypertension associated with eight risk factors. Additionally, we investigated the mediating role of metabolic risk factors on the effects of lifestyle risk factors on hypertension. After adjusting for the sample weight in each country, 26.7% of participants had hypertension. The prevalence of hypertension was highest in those aged ≥65 years, with obesity-associated hypertension (45.7%) exceeding the rates for overweight (32.2%) and non-overweight individuals (18.2%). These eight risk factors collectively explain 83.7% of the PAR% associated with hypertension adjusted for the communal variance. Among the modifiable factors, obesity contributed to a weighted PAR% of 38.2%, while sedentary behaviour and low physical activity combined accounted for a weighted PAR% of 3.1%. Overweight/obesity played a predominant mediating role in the correlation between lifestyle risk factors and systolic and diastolic blood pressure, with the indirect effect accounting for approximately 25-64% and 13-80% of the total effect, respectively. These findings offer new insights into the modified risk factors associated with hypertension in adults in low- and middle-income countries, highlighting the crucial role of maintaining a normal body weight for the effective prevention and management of hypertension.

Predicting cumulative effect of lifestyle risk factors for complex disease

In medical domain, risk factors are often used to model disease predictions. In order to make the most use of the predictive models, linking the model with real patient data generates personalized disease progression and predictions. However, the risk factors are fragmented all over medical literature, certain risks can be accumulated for a disease and the aggregated probability may increase or decrease the occurrence of a disease. In this paper, a risk predictive framework which forms a base for a complete risk prediction model that can be used for various health applications is proposed.

Strong association and effect of lifestyle and clinicopathological risk factors in colorectal cancer during treatment process: a study based on Kashmiri population

Colorectal cancer (CRC) is one of the leading cancer worldwide and alarmingly rising in India. Various lifestyle, clinicopathological and genetic risk factors of CRC have been reported. Individuals with risk factors are more likely to host cancer and are subjected to screening programs. CRC is the fourth most cancer in males and third most in females of the Kashmiri population. This study aims to find out the association and effect of lifestyle risk factors (Smoking and Diet), clinicopathological risk factors (Age, Gender, Metastatic status and Tumor site) and outcome of CRC. This research is a case study that included 222 patients registered in the Shree Maharaja Hari Singh (SMHS) hospital and Sher-i-Kashmir Institute of Medical Sciences, Soura (SKIMS) hospital of Kashmir valley. The information relevant to the aim of study for all CRC patients including various behavioral variables, clinicopathological variables were gathered and reviewed from patient medical records (files), histopathology studies, as well as details collected from patients or guardians (as some critical patients were not able to speak themselves) through personal interviews. The collected data also included symptoms such as abdominal pain, constipation, on and off fever, bleeding and weight loss which were gathered from registered records as well as from patients themselves. This entire study was carried out by the willingness of the patients as they were prior informed about this study. The relevant data particularly included dietary factors, smoking factors, age, gender, tumor site and metastatic status. The outcome of CRC was categorized into three groups: Disease Progression (DP), Partial Response (PR) and Disease-Free (DF); the criteria used for categorizing outcome groups DP, PR and DF were as follows: (1) The patients were categorized as a DF based on clinical examination, i.e., history and physical examination, radiologically, i.e., based on CACT abdomen/MRI PET tests and biochemically, i.e., based on examination of Tumor markers like CEA levels. (2) The patients were kept in the PR category whose disease status was found Stagnant and who showed a decrease in the volume of the tumor arrived at, based on three diagnostic techniques such as clinical, radiological and biochemical examination reports. (3) The patients were under DP whose Increased CEA level showed tumor burden and prognosis and an increase in the volume of the tumor with spread to nearby organs. Smoking (p =0.001), age (p = 7.599e–07), metastatic (p = 2.2e–16) and diet (p = 4.508e–07) showed a highly significant association with CRC outcomes. However, no difference was observed in gender and tumor site. The outcome groups (DP, PR, DF) were also different in mean and showed statistical significance (p = 0.0022). In addition, family-wise comparison in outcome groups was observed statistically significant in between G3 and G1 (i.e., disease-free group and disease progression group) and in G3–G2 (i.e., disease-free group and partial response group). Furthermore, the main effect of chosen risk factors was high in the disease progression group but overall no strong association of effect was found. Risk factors of CRC act as a big impediment during the treatment process leading more patients to disease progression and poor differentiation. More awareness about risk factors is needed to provide a clear picture of the role of risk factors in the development and treatment of CRC.

Combined effects of lifestyle risk factors on fatty liver index

BackgroundFactors of lifestyle may have a major impact on liver-related morbidity and mortality.We examined independent and joint effects of lifestyle risk factors on fatty liver index (FLI), a biomarker of hepatic steatosis, in a population-based cross-sectional national health survey.MethodsThe study included 12,368 participants (5784 men, 6584 women) aged 25–74 years. Quantitative estimates of alcohol use, smoking, adiposity and physical activity were used to establish a total score of risk factors, with higher scores indicating an unhealthier lifestyle. FLI was calculated based on an algorithm including body mass index, waist circumference, serum gamma-glutamyltransferase and triglycerides.ResultsThe occurrence of FLI ≥ 60% indicating fatty liver increased from 2.4% in men with zero risk factors to 81.9% in those with a total risk score of 7–8 (p < 0.0005 for linear trend) and in women from 0 to 73.5% (p < 0.0005). The most striking individual impacts on the likelihood for FLI above 60% were observed for physical inactivity (p < 0.0005 for both genders) and alcohol consumption (p < 0.0005 for men). Interestingly, coffee consumption was also found to increase with increasing risk factor scores (p < 0.0005 for linear trend in both genders).ConclusionsThe data indicates that unfavorable combinations of lifestyle risk factors lead to a high likelihood of hepatic steatosis. Use of FLI as a diagnostic tool may benefit the assessment of interventions aimed at maintaining a healthy lifestyle and prevention of liver-related morbidity.

Lifestyle risk factors, non-communicable diseases and labour force participation in South Africa

ABSTRACTThis paper investigates the indirect effects of lifestyle risk factors associated with non-communicable diseases on labour force participation in South Africa utilising data from the National Income Dynamics Study. Endogenous multivariate probit models with a recursive simultaneous structure were employed in the study as a method of analysis. Findings showed a negative effect of non-communicable diseases on labour force participation. When the analysis was disaggregated by gender, the results showed that the effect of stroke and heart diseases were only significant for men, while diabetes and hypertension were only significant for women. The results also emphasised the significant indirect impact of obesity, physical activity and alcohol consumption on labour force participation through non-communicable diseases, especially for men. The policy implications of this study are thus gender-specific. These results can be used to inform the South African National Department of Health to strengthen current health strategies with the aim of reducing lifestyle risk factors and thus promoting sustained labour force participation rates in South Africa.

Investigating the effect of lifestyle risk factors upon number of aspirated and mature oocytes in in vitro fertilization cycles: Interaction with antral follicle count.

IntroductionThere is evidence demonstrating that certain lifestyle factors have a detrimental effect on fertility. Since such factors often coexist, possible synergistic effects merit further investigation. Thus we aimed to examine the cumulative impact of lifestyle factors on in vitro fertilization (IVF) early reproductive treatment outcomes and their interaction with measures of ovarian reserve.Materials and methodsBy following women who were starting their first fresh IVF cycle in 2 cohorts, the “Lifestyle study cohort” (hypothesis generating cohort, n = 242) and the “UppSTART study” (validation cohort, n = 432) in Sweden, we identified two significant risk factors acting independently, smoking and BMI, and then further assessed their cumulative effects.ResultsWomen with both these risk factors had an Incidence Rate Ratio (IRR) of 0.75 [(95% CI 0.61–0.94)] regarding the number of aspirated oocytes compared to women without these risk factors. Concerning the proportion of mature oocytes in relation to the total number of aspirated oocytes, the interaction between BMI and Antral Follicle Count (AFC) was significant (p-value 0.045): the lower the value of AFC, the more harmful the effect of BMI with the outcome.ConclusionsData shows that there is an individual as well as a cumulative effect of smoking and BMI on the number of aspirated and mature oocytes in fresh IVF treatment cycles. AFC might modify associations between BMI and the proportion of mature oocytes in relation to the total number of aspirated oocytes. These results highlight the importance of lifestyle factors on IVF early reproductive outcomes and provide additional evidence for the importance of preconception guidance for the optimization of IVF cycle outcome.

Flavonoid intake is associated with lower mortality in the Danish Diet Cancer and Health Cohort

Flavonoids, plant-derived polyphenolic compounds, have been linked with health benefits. However, evidence from observational studies is incomplete; studies on cancer mortality are scarce and moderating effects of lifestyle risk factors for early mortality are unknown. In this prospective cohort study including 56,048 participants of the Danish Diet, Cancer, and Health cohort crosslinked with Danish nationwide registries and followed for 23 years, there are 14,083 deaths. A moderate habitual intake of flavonoids is inversely associated with all-cause, cardiovascular- and cancer-related mortality. This strong association plateaus at intakes of approximately 500 mg/day. Furthermore, the inverse associations between total flavonoid intake and mortality outcomes are stronger and more linear in smokers than in non-smokers, as well as in heavy (>20 g/d) vs. low-moderate (<20 g/d) alcohol consumers. These findings highlight the potential to reduce mortality through recommendations to increase intakes of flavonoid-rich foods, particularly in smokers and high alcohol consumers.

Assessing for interaction between APOE ε4, sex, and lifestyle on cognitive abilities.

To test for interactions between APOE ε4 genotype and lifestyle factors on worse cognitive abilities in UK Biobank. Using UK Biobank cohort data, we tested for interactions between APOE ε4 allele presence, lifestyle factors of alcohol intake, smoking, total physical activity and obesity, and sex, on cognitive tests of reasoning, information processing speed, and executive function (n range = 70,988-324,725 depending on the test). We statistically adjusted for potential confounders of age, sex, deprivation, cardiometabolic conditions, and educational attainment. There were significant associations between APOE ε4 and worse cognitive abilities, independent of potential confounders, and between lifestyle risk factors and worse cognitive abilities; however, there were no interactions at multiple correction-adjusted p < 0.05, against our hypotheses. Our results do not provide support for the idea that ε4 genotype increases vulnerability to the negative effects of lifestyle risk factors on cognitive ability, but rather support a primarily outright association between APOE ε4 genotype and worse cognitive ability.

Iranian lifestyle factors affecting reflux disease among healthy people in Qom.

Background and aimGastroesophageal reflux disease (GERD) is one of the most common digestive system disorders. Life style factors may increase the risk of reflux disease. We aimed to determine prevalence of reflux and related life style-factors in the population living in Qom.MethodsThis cross-sectional study was conducted among 1500 residents of Qom in 2014. Individuals were selected through multi-stage sampling. They completed two questionnaires: FSSG questionnaire for diagnosis of GERD and a general questionnaire to measure demographic and lifestyle factors. Univariate and multivariate were used for analysis of data. Data were analyzed using IBM SPSS version 20.ResultsA total of 1130 individuals were analyzed in which 52.4% of them were female. Prevalence of GERD was 28%. Adjusted findings showed use of PPIs (OR: 2.2, 95% CI: 2–5), taking H2RAs (OR: 4.7, 95% CI: 2.3–9.4), the habit of quick eating (OR: 1.5, 95% CI: 1.1–2), extra salt consumption on daily meals (OR: 1.5, 95% CI: 1.05–2), lack of sleep (OR: 2.6, 95% CI: 1.5–4.8), and consumption of white bread (OR: 1.7, 95% CI: 1.05–2.7) were related to increased risk of GERD.ConclusionOur findings showed lifestyle factors such as habit of quick eating, extra salt on regular meals, lack of sleep and use of white bread were associate with increased risk of GERD. However, habit of midnight snack, having dinner just before bedtime, lack of breakfast, smoking, drinking tea and coffee were not associated with increased risk of GERD. It is recommended to carry out a cohort study among the Iranian population to evaluate the effect of life-style risk factors on GERD.

Lifestyle Risk Factors Increase the Risk of Hospitalization for Sciatica: Findings of Four Prospective Cohort Studies

BackgroundThe purpose of this study is to assess the effects of lifestyle risk factors on the risk of hospitalization for sciatica and to determine whether overweight or obesity modifies the effect of leisure-time physical activity on hospitalization for sciatica. MethodsWe included 4 Finnish prospective cohort studies (Health 2000 Survey, Mobile Clinic Survey, Helsinki Health Study, and Young Finns Study) consisting of 34,589 participants and 1259 hospitalizations for sciatica during 12 to 30 years of follow-up. Sciatica was based on hospital discharge register data. We conducted a random-effects individual participant data meta-analysis. ResultsAfter adjustment for confounding factors, current smoking at baseline increased the risk of subsequent hospitalization for sciatica by 33% (95% confidence interval [CI], 13%-56%), whereas past smokers were no longer at increased risk. Obesity defined by body mass index increased the risk of hospitalization for sciatica by 36% (95% CI 7%-74%), and abdominal obesity defined by waist circumference increased the risk by 41% (95% CI 3%-93%). Walking or cycling to work reduced the risk of hospitalization for sciatica by 33% (95% CI 4%-53%), and the effect was independent of body weight and other leisure activities, while other types of leisure activities did not have a statistically significant effect. ConclusionsSmoking and obesity increase the risk of hospitalization for sciatica, whereas walking or cycling to work protects against hospitalization for sciatica. Walking and cycling can be recommended for the prevention of sciatica in the general population.

Relationship of Lifetime Exposure to Tobacco, Alcohol and Second Hand Tobacco Smoke with Upper aero-digestive tract cancers in India: a Case-Control Study with a Life-Course Perspective

Background:Squamous cell carcinomas of the upper aero-digestive tract (UADTSCC) are a multifaceted public health problem. Effects of lifestyle risk factors, including tobacco (chewing and smoking), alcohol drinking and exposure to second hand tobacco smoke (SHS) at home and their association with UADT cancers was assessed in a case-control study with a life-course perspective. The study was conducted at two different hospitals in Pune, India.Material and methods:The total sample size (N=480) included 240 histopathologically confirmed cases of UADT cancers and an equal number of controls frequency matched with cases by gender and age distribution (+5 years). All the patients were interviewed face-face using structured questionnaires. Self-reported information on socio-demographic and lifestyle risk factors from childhood to the date of diagnosis of disease/cancer was obtained. Frequency, duration and age of initiation of habits were also recorded to study dose-response relationships. Odds ratios and their 95% confidence intervals were calculated through unconditional logistic regression, adjusting for relevant potential confounders.Results:Chewing tobacco emerged as the strongest predictor for UADT cancers (OR=7.61; 95% CI 4.65-12.45) in comparison to smoking and drinking alcohol. Exposure to SHS during childhood (<16 years) rather than ≥16 years increased the risk (OR=4.05; 95% CI 2.06-7.95). Combined effects of tobacco and alcohol consumption habits elevated the risk by twelve fold (OR=12.05; 95% 4.61-31.49) in comparison to never users of these habits. Furthermore, the combination of these lifestyle risk factors accounted for 86.8% of population attributable risk.Conclusions:Early exposure to various modifiable lifestyle risk factors has a strong positive association with UADT cancer incidence. Effective future public health interventions with focus on vital time points in life targeting these risk factors could possibly be a major step in primary prevention and control of this cancer at the population level.

Cardiovascular Risk Factors Associated With Blood Metabolite Concentrations and Their Alterations During a 4-Year Period in a Population-Based Cohort.

The effects of lifestyle risk factors considered collectively on the human metabolism are to date unknown. We aim to investigate the association of these risk factors with metabolites and their changes during 4 years. One hundred and sixty-three metabolites were measured in serum samples with the AbsoluteIDQ kit p150 (Biocrates) following a targeted metabolomics approach, in a population-based cohort of 1030 individuals, aged 45 to 83 years at baseline. We evaluated associations between metabolite concentrations (28 acylcarnitines, 14 amino acids, 9 lysophosphocholines, 72 phosphocholines, 10 sphingomyelins and sum of hexoses) and 5 lifestyle risk factors (body mass index [BMI], alcohol consumption, smoking, diet, and exercise). Multilevel or simple linear regression modeling adjusted for relevant covariates was used for the evaluation of cross-sectional or longitudinal associations, respectively; multiple testing correction was based on false discovery rate. BMI, alcohol consumption, and smoking were associated with lipid metabolism (reduced lyso- and acyl-alkyl-phosphatidylcholines and increased diacylphosphatidylcholines concentrations). Smoking showed positive associations with acylcarnitines, and BMI correlated inversely with nonessential amino acids. Fewer metabolites showed relative changes that were associated with baseline risk factors: increases in 5 different acyl-alkyl phosphatidylcholines were associated with lower alcohol consumption and BMI and with a healthier diet. Increased levels of tyrosine were associated with BMI. Sex-specific effects of smoking and BMI were found specifically related to acylcarnitine metabolism: in women higher BMI and in men more pack-years were associated with increases in acylcarnitines. This study showed sex-specific effects of lifestyle risks factors on human metabolism and highlighted their long-term metabolic consequences.

Socioeconomic Status and the Prevalence of Type 2 Diabetes Among Adults in Northwest China.

The purpose of the study was to investigate (1) the associations of socioeconomic status, lifestyle risk factors, and the prevalence of newly diagnosed type 2 diabetes and (2) the mediating effects of lifestyle risk factors on the association of socioeconomic status and the prevalence of newly diagnosed type 2 diabetes among Chinese adults in northwest China. Based on a correlational design and random multistage sampling in communities (N = 3243), data were collected through face-to-face interviews and anthropometric measurements. Education, occupation, and income were considered indicators of socioeconomic status. Approximately 7.5% persons interviewed had newly diagnosed type 2 diabetes. Chi-square analyses showed that higher socioeconomic indicators (higher income, nonmanual occupation) were associated with increased risk. Lifestyle risk factors, including alcohol use, unhealthy diet, and higher body mass index, were significantly positively associated with type 2 diabetes. Adjusting for demographic characteristics, hierarchical logistic regression analyses showed that unhealthy diet and high body mass index were significantly associated with type 2 diabetes. Higher incomes and nonmanual occupations were related to a greater prevalence of type 2 diabetes, and high body mass index mediated these associations. These findings suggest that interventions for type 2 diabetes in China should be targeted at populations with high socioeconomic status and nonmanual occupations to reduce lifestyle risk factors and prevent diabetes.

Does family history of cancer modify the effects of lifestyle risk factors on esophageal cancer? a population‐based case–control study in China

A population-based case-control study on esophageal cancer has been conducted since 2003 in Jiangsu Province, China. The aim of this analysis is to provide further evidence on the relationship between family history of cancer in first-degree relatives (FH-FDRs) and the risk of esophageal cancer, and to explore the joint effects for FH-FDR with major lifestyle risk factors. A total of 1,520 cases and 3,879 controls were recruited. Unconditional logistic regression was applied for evaluating independent association as well as potential interactions between FH-FDR and lifestyle risk factors on the risk of esophageal cancer. Population attributable fraction (PAF) was calculated to quantify the proportion of cases attributable to risk factors. Results showed that with a FH-FDR of any malignant tumor or esophageal cancer, there is a 1.64- and 2.22-fold risk of esophageal cancer, respectively. Association was increased when there was more than one affected FDR (OR = 3.14) and younger age at diagnosis of relatives. Exposure of both FH-FDR and lifestyle risk factors strongly associated with esophageal cancer. Significant superadditivity interaction was found for FH-FDR with fast eating speed and diets low in fruits and vegetables. The estimation of PAF indicated that the majority of cases were attributed to lifestyle risk factors. In conclusion, it was found that FH-FDR significantly increases the risk of esophageal cancer and could modify the effect of certain lifestyle risk factors. If comprehensive lifestyle interventions are carried out within high-risk populations, there is a high probability of curbing occurrences of esophageal cancer.

Beyond Established and Novel Risk Factors

Dyslipidemia, hypertension, and diabetes mellitus have been appropriately highlighted as established predictors of cardiovascular disease. These risk factors have become preeminent targets for influencing cardiovascular risk; their assessment, treatment, and monitoring are major emphases of clinical care, research investigation, treatment guidelines, organization position papers, and measures of physician and hospital performance. Notably, lifestyle risk factors, including dietary habits, physical inactivity, smoking, and adiposity, strongly influence the established cardiovascular risk factors and also affect novel pathways of risk such as inflammation/oxidative stress, endothelial function, thrombosis/coagulation, and arrhythmia. Furthermore, modest alterations of these lifestyle risk factors are achievable and have substantial effects on cardiovascular risk. Thus, basic lifestyle habits should be considered fundamental risk factors for cardiovascular disease. Although efforts to combat established and novel risk factors with pharmacological treatments are important and should continue, we call for a systematic rebalancing of current research, clinical care, and policy efforts to focus more on lifestyle. The rising costs of healthcare and the epidemics of overweight and obesity highlight the inadequacies of our current strategy. Substantially more resources should be directed toward research on lifestyle risk factors, their determinants, and effective interventions to change them. The clinical evaluation and treatment of dietary, physical activity, and smoking habits must become as routine and familiar as assessment of blood pressure, cholesterol, and glucose levels. Major policy initiatives and reimbursement guidelines must also be rebalanced to emphasize lifestyle risk factors. Cardiovascular diseases are leading causes of death and disability among men and women in nearly all nations.1 Identification of persons at higher or lower risk for cardiovascular events is important to facilitate effective use of resources and interventions to reduce disease burden among individuals and in society. Each of the established risk factors for cardiovascular disease—age, gender, dyslipidemia, hypertension, diabetes mellitus, and smoking—have been appropriately highlighted …

Risk Factors for Bladder Cancer

To summarize risk factors for bladder cancer, emphasizing the role of recently established associations and to present some ongoing debates on the issue. A systematic literature search was performed using MEDLINE database on bladder cancer risk factors between January 1985 and June 2006 and by detailed examination of the references of original articles, reviews and monographs retrieved. Cigarette smoking is recognized as the main cause of bladder cancer and accounts for about 50% of cases in developed countries. A strong link exists between the amount and duration of cigarette smoking. A high risk of bladder carcinoma has been observed in workers exposed to some aromatic amines. Based on these and other occupational risks, it has been estimated that 5-10% of bladder carcinomas in industrialized countries were due to exposures of occupational origin. Infectious agents have a major influence on bladder cancer risks in the areas of the world where Schistosoma haematobium infestation is endemic. Other potential risk factors for bladder cancer are other urinary tract infections and drinking tap water with chlorination by-products or arsenic. Exposure to certain drugs, like cyclophosphamide used in chemotherapy and heavy consumption of phenacetin-containing analgesics, has been shown to cause bladder cancer in humans. Total fluid intake and high consumption of fruits and vegetables are probably associated with a small decrease in risk. Avoidance of tobacco smoking and incriminated occupational exposures, habitual intake of fresh fruits and vegetables, and prevention and control of urinary tract infections should be recommended for bladder cancer prevention. Further studies are required to assess the role of genetic polymorphisms and their modifying effect of lifestyle risk factors for bladder cancer occurrence and to evaluate the benefit of bladder cancer screening, particularly in those at high risk.

Does educational level influence the effects of smoking, alcohol, physical activity, and obesity on mortality? A prospective population study

Objectives: This study aims at examining whether the relation between established risk factors and mortality differs with socioeconomic status as measured by level of education. Methods: A population-based sample of 14,399 women and 16,236 men aged 20 - 93 years from Copenhagen was stratified into three educational levels measured as basic schooling, and the effect of smoking habits, alcohol consumption, physical activity, and body mass index, respectively, on mortality was assessed. Results: Those with the lowest level of education were most frequently heavy smokers, heavy drinkers, physically inactive, and obese. During a mean follow up of 16 years 10,952 subjects died. Compared with subjects with the lowest educational level, women with the highest educational level had a relative risk of 0.80 (95% CI; 0.70 - 0.91), and men of 0.71 (0.65 - 0.78). Heavy smoking compared with never smoking implied a more than twofold increased risk at all three educational levels among both men and women. The relation between alcohol intake and mortality was J-shaped on all three educational levels. There were decreasing risk functions describing the relations between physical activity and mortality on all three strata. Further, subjects who were either very lean or obese had increased risks of death compared with those of normal weight at all educational levels in both genders. Conclusions: The difference in distribution of the main known risk factors may be part of the explanation for the differences in mortality risk. However, these risk factors seem to influence mortality equally at different educational levels. Therefore, social inequalities in mortality do not seem to be explained only by differences in effect of lifestyle risk factors, but are also related to the social rank or unexamined factors within.

Does educational level influence the effects of smoking, alcohol, physical activity, and obesity on mortality? A prospective population study.

This study aims at examining whether the relation between established risk factors and mortality differs with socioeconomic status as measured by level of education. A population-based sample of 14,399 women and 16,236 men aged 20-93 years from Copenhagen was stratified into three educational levels measured as basic schooling, and the effect of smoking habits, alcohol consumption, physical activity, and body mass index, respectively, on mortality was assessed. Those with the lowest level of education were most frequently heavy smokers, heavy drinkers, physically inactive, and obese. During a mean follow up of 16 years 10,952 subjects died. Compared with subjects with the lowest educational level, women with the highest educational level had a relative risk of 0.80 (95% CI; 0.70-0.91), and men of 0.71 (0.65-0.78). Heavy smoking compared with never smoking implied a more than twofold increased risk at all three educational levels among both men and women. The relation between alcohol intake and mortality was J-shaped on all three educational levels. There were decreasing risk functions describing the relations between physical activity and mortality on all three strata. Further, subjects who were either very lean or obese had increased risks of death compared with those of normal weight at all educational levels in both genders. The difference in distribution of the main known risk factors may be part of the explanation for the differences in mortality risk. However, these risk factors seem to influence mortality equally at different educational levels. Therefore, social inequalities in mortality do not seem to be explained only by differences in effect of lifestyle risk factors, but are also related to the social rank or unexamined factors within.

Nurses' Health Study: Log-Incidence Mathematical Model of Breast Cancer Incidence

In 1983, Pike et al. developed a mathematical model to quantify the effects of reproductive risk factors on the incidence of breast cancer. In 1994, we modified that model to correct some deficiencies in the original model, including a lack of terms for spacing of births and an inability to easily accommodate births after age 40 years. Our extended Pike model, while improving on the original, still has serious disadvantages, such as difficulty in translating model parameters into relative risks (RRs) and an incomplete fit to data that slightly overestimated incidence for premenopausal women with an early age at first birth and that underestimated incidence for post-menopausal women with a late age at first birth. We undertook both the development of a new mathematical model to quantify the effects of reproductive risk factors on breast cancer incidence and validation of the model. A new log-incidence model of breast cancer incidence was developed using nonlinear regression methods, and a study population consisting of 89,132 women in the Nurses' Health Study from which a total of 2249 incident cases of breast cancer were identified. Subjects were followed from the return of the 1976 Nurses' Health Study questionnaire until June 1, 1990, or until the last questionnaire was returned, until the development of any cancer, or until death, yielding 1,148,593 person-years of follow-up. The log-incidence models were fitted using iteratively reweighted least squares analysis. The log-incidence model provided a better fit to that data than the extended Pike model, with parameter estimates interpretable in terms of RRs. This new model can be fitted using standard commercially available statistical software. In the model, younger parous women are generally at slightly higher risk than nulliparous women, which is true for both the observed and expected RRs, and older parous women, aged 55-64 years with an early age at first birth, are at lower risk than nulliparous women,while older women with a late age at first birth are at substantially higher risk than nulliparous women. Log-incidence models, such as this one, provide an efficient framework for modeling the effect of lifestyle risk factors on breast cancer incidence that may be specifically targeted to certain time periods of a woman's reproductive life.