Lifetime and 10-year risks of cardiovascular mortality in relation to risk factors in middle and old age: 50-year follow-up of the Whitehall study of London Civil Servants.

BACKGROUND: Cardiovascular disease (CVD)-related mortality has declined substantially in the United Kingdom (UK) in recent decades, but the continued relevance of conventional risk factors for prediction of CVD mortality throughout the life-course is uncertain. We compared the 10-year risks and lifetime risks of CVD mortality associated with conventional risk factors recorded in middle and old age. METHODS: The Whitehall study was a prospective study of 19,019 male London civil servants (mean age 52 years) when enrolled in 1967-1970 and followed-up for 50 years for cause-specific mortality. In 1997, 7044 (83%) survivors (mean age 77 years) were re-surveyed. The 10-year and lifetime risks of CVD mortality were estimated by levels of CVD risk factors recorded in middle-age and old-age, respectively. RESULTS: By July 2020, 97% had died (22%, 51% and 80% before age 70, 80 and 90 years, respectively) and 7944 of 17,673 deaths (45%) were from CVD. The 10-year and lifetime risks of CVD death increased linearly with higher levels of CVD risk factors recorded in middle-age and in old-age. Individuals in the top versus bottom 5% of CVD risk scores in middle age had a 10.3% (95% CI:7.2-13.4) vs 0.6% (0.1-1.2) 10-year risk of CVD mortality, a 61.4% (59.4-65.3) vs 31.3% (24.1-34.5) lifetime risk of CVD mortality and a 12-year difference in life expectancy from age 50 years. The corresponding differences using a CVD risk score in old-age were 11.0% (4.4-17.5) vs 0.8% (0.0-2.2) for 10-year risk and 42.1% (28.2-50.0) vs 30.3% (6.0-38.0) for lifetime risk of CVD mortality and a 6-year difference in life expectancy from age 70 years. CONCLUSIONS: Conventional risk factors remained highly predictive of CVD mortality and life expectancy through the life-course. The findings highlight the relevance of estimation of both lifetime risks of CVD and 10-year risks of CVD for primary prevention of CVD.

Prostate cancer risk related to foods, food groups, macronutrients and micronutrients derived from the UK Dietary Cohort Consortium food diaries.

BACKGROUND/OBJECTIVES: The influence of dietary factors remains controversial for screen-detected prostate cancer and inconclusive for clinically detected disease. We aimed to examine these associations using prospectively collected food diaries. SUBJECTS/METHODS: A total of 1,717 prostate cancer cases in middle-aged and older UK men were pooled from four prospective cohorts with clinically detected disease (n=663), with routine data follow-up (means 6.6-13.3 years) and a case-control study with screen-detected disease (n=1054), nested in a randomised trial of prostate cancer treatments (ISCTRN 20141297). Multiple-day food diaries (records) completed by men prior to diagnosis were used to estimate intakes of 37 selected nutrients, food groups and items, including carbohydrate, fat, protein, dairy products, fish, meat, fruit and vegetables, energy, fibre, alcohol, lycopene and selenium. Cases were matched on age and diary date to at least one control within study (n=3528). Prostate cancer risk was calculated, using conditional logistic regression (adjusted for baseline covariates) and expressed as odds ratios in each quintile of intake (±95% confidence intervals). Prostate cancer risk was also investigated by localised or advanced stage and by cancer detection method. RESULTS: There were no strong associations between prostate cancer risk and 37 dietary factors. CONCLUSIONS: Prostate cancer risk, including by disease stage, was not strongly associated with dietary factors measured by food diaries in middle-aged and older UK men.

Interleukin-6 as a predictor of symptom resolution in psychological distress: a cohort study.

BACKGROUND: Elevated levels of interleukin-6 (IL-6) have been associated with the development of common mental disorders, such as depression, but its role in symptom resolution is unclear. METHOD: We examined the association between IL-6 and symptom resolution in a non-clinical sample of participants with psychological distress. RESULTS: Relative to high IL-6 levels, low levels at baseline were associated with symptom resolution at follow-up [age- and sex-adjusted risk ratio (RR) = 1.15, 95% confidence interval (CI) 1.06-1.25]. Further adjustment for covariates had little effect on the association. Symptomatic participants with repeated low IL-6 were more likely to be symptom-free at follow-up compared with those with repeated high IL-6 (RR = 1.21, 95% CI 1.03-1.41). Among the symptomatic participants with elevated IL-6 at baseline, IL-6 decreased along with symptom resolution. CONCLUSIONS: IL-6 is potentially related to the mechanisms underlying recovery from symptoms of mental ill health. Further studies are needed to examine these mechanisms and to confirm the findings in relation to clinical depression.

Job strain and the risk of severe asthma exacerbations: a meta-analysis of individual-participant data from 100 000 European men and women.

BACKGROUND: Many patients and healthcare professionals believe that work-related psychosocial stress, such as job strain, can make asthma worse, but this is not corroborated by empirical evidence. We investigated the associations between job strain and the incidence of severe asthma exacerbations in working-age European men and women. METHODS: We analysed individual-level data, collected between 1985 and 2010, from 102 175 working-age men and women in 11 prospective European studies. Job strain (a combination of high demands and low control at work) was self-reported at baseline. Incident severe asthma exacerbations were ascertained from national hospitalization and death registries. Associations between job strain and asthma exacerbations were modelled using Cox regression and the study-specific findings combined using random-effects meta-analyses. RESULTS: During a median follow-up of 10 years, 1 109 individuals experienced a severe asthma exacerbation (430 with asthma as the primary diagnostic code). In the age- and sex-adjusted analyses, job strain was associated with an increased risk of severe asthma exacerbations defined using the primary diagnostic code (hazard ratio, HR: 1.27, 95% confidence interval, CI: 1.00, 1.61). This association attenuated towards the null after adjustment for potential confounders (HR: 1.22, 95% CI: 0.96, 1.55). No association was observed in the analyses with asthma defined using any diagnostic code (HR: 1.01, 95% CI: 0.86, 1.19). CONCLUSIONS: Our findings suggest that job strain is probably not an important risk factor for severe asthma exacerbations leading to hospitalization or death.

Conflicts between work and family life and subsequent sleep problems among employees from Finland, Britain, and Japan.

PURPOSE: Research on the association between family-to-work and work-to-family conflicts and sleep problems is sparse and mostly cross-sectional. We examined these associations prospectively in three occupational cohorts. METHODS: Data were derived from the Finnish Helsinki Health Study (n = 3,881), the British Whitehall II Study (n = 3,998), and the Japanese Civil Servants Study (n = 1,834). Sleep problems were assessed using the Jenkins sleep questionnaire in the Finnish and British cohorts and the Pittsburgh Sleep Quality Index in the Japanese cohort. Family-to-work and work-to-family conflicts measured whether family life interfered with work or vice versa. Age, baseline sleep problems, job strain, and self-rated health were adjusted for in logistic regression analyses. RESULTS: Adjusted for age and baseline sleep, strong family-to-work conflicts were associated with subsequent sleep problems among Finnish women (OR, 1.33 (95 % CI, 1.02-1.73)) and Japanese employees of both sexes (OR, 7.61 (95 % CI, 1.01-57.2) for women; OR, 1.97 (95 % CI, 1.06-3.66) for men). Strong work-to-family conflicts were associated with subsequent sleep problems in British, Finnish, and Japanese women (OR, 2.36 (95 % CI, 1.42-3.93), 1.62 (95 % CI, 1.20-2.18), and 5.35 (95 % CI, 1.00-28.55), respectively) adjusted for age and baseline sleep problems. In men, this association was seen only in the British cohort (OR, 2.02 (95 % CI, 1.42-2.88)). Adjustments for job strain and self-rated health produced no significant attenuation of these associations. CONCLUSION: Family-to-work and work-to-family conflicts predicted subsequent sleep problems among the majority of employees in three occupational cohorts.

Vitamin C intake from diary recordings and risk of breast cancer in the UK Dietary Cohort Consortium.

BACKGROUND/OBJECTIVES: Vitamin C intake has been inversely associated with breast cancer risk in case-control studies, but not in meta-analyses of cohort studies using Food Frequency Questionnaires, which can over-report fruit and vegetable intake, the main source of vitamin C. This is the first study to investigate associations between vitamin C intake and breast cancer risk using food diaries. SUBJECTS/METHODS: Estimated dietary vitamin C intake was derived from 4-7 day food diaries pooled from five prospective studies in the UK Dietary Cohort Consortium. This nested case-control study of 707 incident breast cancer cases and 2144 matched controls examined breast cancer risk in relation to dietary vitamin C intake using conditional logistic regression adjusting for relevant covariates. Additionally, total vitamin C intake from supplements and diet was analysed in three cohorts. RESULTS: No evidence of associations was observed between breast cancer risk and vitamin C intake analysed for dietary vitamin C intake (odds ratios (OR)=0.98 per 60 mg/day, 95% confidence interval (CI): 0.88-1.09, P (trend)=0.7), dietary vitamin C density (OR=0.97 per 60 mg/day, 95% CI: 0.87-1.07, P (trend)=0.5 ) or total vitamin C intake (OR=1.01 per 60 mg/day, 95% CI: 0.99-1.03, P (trend)=0.3). Additionally, there was no significant association for post-menopausal women (OR=1.02 per 60 mg/day, 95% CI: 0.99-1.05, P (trend)=0.3). CONCLUSIONS: This pooled analysis of individual UK women found no evidence of significant associations between breast cancer incidence and dietary or total vitamin C intake derived uniquely from detailed diary recordings.

Long working hours and symptoms of anxiety and depression: a 5-year follow-up of the Whitehall II study.

BACKGROUND: Although long working hours are common in working populations, little is known about the effect of long working hours on mental health. METHOD: We examined the association between long working hours and the onset of depressive and anxiety symptoms in middle-aged employees. Participants were 2960 full-time employees aged 44 to 66 years (2248 men, 712 women) from the prospective Whitehall II cohort study of British civil servants. Working hours, anxiety and depressive symptoms, and covariates were measured at baseline (1997-1999) followed by two subsequent measurements of depressive and anxiety symptoms (2001 and 2002-2004). RESULTS: In a prospective analysis of participants with no depressive (n=2549) or anxiety symptoms (n=2618) at baseline, Cox proportional hazard analysis adjusted for baseline covariates showed a 1.66-fold [95% confidence interval (CI) 1.06-2.61] risk of depressive symptoms and a 1.74-fold (95% CI 1.15-2.61) risk of anxiety symptoms among employees working more than 55 h/week compared with employees working 35-40 h/week. Sex-stratified analysis showed an excess risk of depression and anxiety associated with long working hours among women [hazard ratios (HRs) 2.67 (95% CI 1.07-6.68) and 2.84 (95% CI 1.27-6.34) respectively] but not men [1.30 (0.77-2.19) and 1.43 (0.89-2.30)]. CONCLUSIONS: Working long hours is a risk factor for the development of depressive and anxiety symptoms in women.

Incidence and prognosis of angina pectoris in South Asians and Whites: 18 years of follow-up over seven phases in the Whitehall-II prospective cohort study.

BACKGROUND: Whether the higher coronary mortality in South Asians compared with White populations is due to a higher incidence of disease is not known. This study assessed cumulative incidence of chest pain in South Asians and Whites, and prognosis of chest pain. METHODS: Over seven phases of 18-year follow-up of the Whitehall-II study (9,775 civil servants: 9,195 White, 580 South Asian), chest pain was assessed using the Rose questionnaire. Coronary death/non-fatal myocardial infarction was examined comparing those with chest pain to those with no chest pain at baseline. RESULTS: South Asians had higher cumulative frequencies of typical angina by Phase 7 (17.0 versus 11.3%, P < 0.001) and exertional chest pain (15.4 versus 8.5%, P < 0.001) compared with Whites. Typical angina and exertional chest pain at baseline were associated with a worse prognosis compared with those with no chest pain in both groups (typical angina, South Asians: HR, 4.67 and 95% CI, 2.12-0.30; Whites: HR, 3.56 95% CI, 2.59-4.88). Baseline non-exertional chest pain did not confer a worse prognosis. Across all types of pain, prognosis was worse in South Asians. CONCLUSION: South Asians had higher cumulative incidence of angina than Whites. In both, typical angina and exertional chest pain were associated with worse prognosis compared with those with no chest pain.

Alcohol intake and risk of colorectal cancer: results from the UK Dietary Cohort Consortium.

BACKGROUND: Epidemiological studies have suggested that excessive alcohol intake increases colorectal cancer (CRC) risk. However, findings regarding tumour subsites and sex differences have been inconsistent. METHODS: We investigated the prospective associations between alcohol intake on overall and site- and sex-specific CRC risk. Analyses were conducted on 579 CRC cases and 1996 matched controls nested within the UK Dietary Cohort Consortium using standardised data obtained from food diaries as a main nutritional method and repeated using data from food frequency questionnaire (FFQ). RESULTS: Compared with individuals in the lightest category of drinkers (>0-<5 g per day), the multivariable odds ratios of CRC were 1.16 (95% confidence interval (95% CI): 0.88, 1.53) for non-drinkers, 0.91 (95% CI: 0.67, 1.24) for drinkers with 5-<15 g per day, 0.90 (95% CI: 0.65, 1.25) for drinkers with 15-<30 g per day, 1.02 (95% CI: 0.66, 1.58) for drinkers with 30-<45 g per day and 1.19 (95% CI: 0.75, 1.91) for drinkers with >or=45 g per day. No clear associations were observed between site-specific CRC risk and alcohol intake in either sex. Analyses using FFQ showed similar results. CONCLUSION: We found no significantly increased risk of CRC up to 30 g per day of alcohol intake within the UK Dietary Cohort Consortium.

Do the Joint British Society (JBS2) guidelines on prevention of cardiovascular disease with respect to plasma glucose improve risk stratification in the general population? Prospective cohort study.

AIMS: British guidelines on vascular disease prevention recommend adding a random (casual) blood glucose measurement to a lipid profile in those aged > or = 40 years. To assess this recommendation, we compared the predictive value of a risk model based on the Framingham risk score alone to one which additionally included information on fasting blood glucose, with respect to incident coronary heart disease (CHD) over 11 years. METHOD: Men and women aged 40-63 years in Whitehall II were followed up for incident CHD: death/non-fatal myocardial infarction; angina confirmed by doctor diagnosis or electrocardiogram (ECG) and all first events. Fasting blood glucose was specified as a continuous variable or categorized by World Health Organization (WHO) 1999 glycaemic status (normal glucose tolerance, impaired fasting glucose or newly diagnosed diabetes). RESULTS: The hazard ratio for incident CHD was 1.10 (95%CI 1.09; 1.12) in men and 1.13 (1.10; 1.17) in women per percentage point increase in Framingham risk. The excess risk remained unchanged in models which added glycaemic status or continuous fasting glucose. The area under the receiver operating characteristic (ROC) curve for the Framingham score and incident coronary heart disease [0.70 (0.68; 0.73)] did not change when glycaemic status or fasting glucose was added to the prediction model. Reclassification with these modified models improved discrimination based on the Framingham score alone when glycaemic status was added, net reclassification improvement 2.4% (95% CI 0.2%; 4.6%), but not when fasting glucose was added. CONCLUSION: Better detection of unrecognized diabetes is a valuable consequence of including a random blood glucose in a vascular risk profile. Our results suggest that this strategy is unlikely to improve risk stratification for CHD.

Work disability following major organisational change: the Whitehall II study.

BACKGROUND: Privatisation and private sector practices have been increasingly applied to the public sector in many industrialised countries. Over the same period, long-term work disability has risen substantially. We examined whether a major organisational change--the transfer of public sector work to executive agencies run on private sector lines--was associated with an increased risk of work disability. METHODS: The study uses self-reported data from the prospective Whitehall II cohort study. Associations between transfer to an executive agency assessed at baseline (1991-1994) and work disability ascertained over a period of approximately 8 years at three follow-up surveys (1995-1996, 1997-1999 and 2001) were examined using Cox proportional hazard models. RESULTS: In age- and sex-adjusted models, risk of work disability was higher among the 1263 employees who were transferred to an executive agency (HR 1.90, 95% CI 1.46 to 2.48) compared with the 3419 employees whose job was not transferred. These findings were robust to additional adjustment for physical and mental health and health behaviours at baseline. CONCLUSIONS: Increased work disability was observed among employees exposed to the transfer of public sector work to executive agencies run on private sector lines. This may highlight an unintentional cost for employees, employers and society.

Performance of existing risk scores in screening for undiagnosed diabetes: an external validation study.

AIM: To compare the performance of nine published strategies for the selection of individuals prior to screening for undiagnosed diabetes. METHODS: We conducted a validation study, based on a cross-sectional analysis of 6990 participants of the Whitehall II study, an occupational cohort of civil servants in London. We calculated sensitivity, specificity and the area under the receiver operating characteristic (ROC) curve, indicative of the ability of a risk score to correctly identify those with undiagnosed diabetes. RESULTS: The prevalence of unknown diabetes was 2.0%. At a set level of sensitivity (0.70), the specificity of the different scores ranged between 0.41 and 0.57. A reference model, based solely on age and body mass index had an area under the ROC curve of 0.67 [95% confidence interval (CI): 0.62, 0.72]. Four scores had a lower area under the ROC curve (lowest ROC AUC: 0.62; 95% CI: 0.58, 0.67) compared with the reference model, while the other five scores had similar areas (highest ROC AUC: 0.68; 95% CI: 0.63, 0.72). All ROC curve areas were lower than those reported in the original publications and validation studies. CONCLUSIONS: Existing risk scores for the detection of undiagnosed diabetes perform less well in a large validation cohort compared with previous validation studies. Our study indicates that non-invasive risk scores require further refinement and testing before they can be used as the first step in a diabetes screening programme.

The association of cognitive performance with mental health and physical functioning strengthens with age: the Whitehall II cohort study.

BACKGROUND: Cognitive performance has been associated with mental and physical health, but it is unknown whether the strength of these associations changes with ageing and with age-related social transitions, such as retirement. We examined whether cognitive performance predicted mental and physical health from midlife to early old age. METHOD: Participants were 5414 men and 2278 women from the Whitehall II cohort study followed for 15 years between 1991 and 2006. The age range included over the follow-up was from 40 to 75 years. Mental health and physical functioning were measured six times using SF-36 subscales. Cognitive performance was assessed three times using five cognitive tests assessing verbal and numerical reasoning, verbal memory, and phonemic and semantic fluency. Socio-economic status (SES) and retirement were included as covariates. RESULTS: High cognitive performance was associated with better mental health and physical functioning. Mental health differences associated with cognitive performance widened with age from 39 to 76 years of age, whereas physical functioning differences widened only between 39 and 60 years and not after 60 years of age. SES explained part of the widening differences in mental health and physical functioning before age 60. Cognitive performance was more strongly associated with mental health in retired than non-retired participants, which contributed to the widening differences after 60 years of age. CONCLUSIONS: The strength of cognitive performance in predicting mental and physical health may increase from midlife to early old age, and these changes may be related to SES and age-related transitions, such as retirement.

Cardiorespiratory risk factors as predictors of 40-year mortality in women and men.

OBJECTIVE: Most historical studies of cardiorespiratory risk factors as predictors of mortality have been based on men. This study examines whether they predict mortality over long periods in women and men. DESIGN: Prospective cohort study. SETTING: Participants were employees of the General Post Office. METHODS: Risk factor data were collected via clinical examination and questionnaire, 1966-7. Associations between cardiorespiratory risk factors and 40-year mortality were determined for 644 women and 1272 men aged 35-70 at examination. MAIN OUTCOME MEASURES: All-cause, cardiovascular (CVD), cancer and respiratory mortality. RESULTS: Associations between systolic blood pressure and all-cause and stroke mortality were equally strong for women and men, hazard ratio (95% confidence interval) 1.25 (1.1 to 1.4) and 1.18 (1.1 to 1.3); and 2.17 (1.7 to 2.8) and 1.69 (1.4 to 2.1), respectively. Cholesterol was higher in women and was associated with all-cause 1.22 (1.1 to 1.4) and CVD 1.39 (1.2 to 1.7) mortality, while associations between 2-hour glucose and all-cause 1.15 (1.1 to 1.2), coronary heart disease (CHD) 1.25 (1.1 to 1.4) and respiratory mortality 1.21 (1.0 to 1.5) were observed in men. Obesity was associated with stroke in women (2.42 (1.12 to 5.24)) and CHD in men (1.59 (1.02 to 2.49)), while ECG ischaemia was associated with CVD in both sexes. The strongest, most consistent predictor of mortality was smoking in women and poor lung function in men. However, evidence of sex differences in associations between the cardiorespiratory risk factors measured and mortality was sparse. CONCLUSIONS: Data from a 40-year follow-up period show remarkably persistent associations between risk factors and cardiorespiratory and all-cause mortality in women and men.

Cumulative exposure to high-strain and active jobs as predictors of cognitive function: the Whitehall II study.

OBJECTIVES: A high-strain job (a combination of high job demands and low job control) is expected to increase the risk of health problems, whereas an active job (high demands and high control) can be hypothesised to be associated with a greater capacity to learn. We tested associations between high-strain and active jobs and cognitive function in middle-aged men and women. METHODS: Data on 4146 British civil servants (2989 men and 1157 women) aged 35-55 years at baseline came from the Whitehall II study. Cumulative exposure to both high-strain and active jobs was assessed at phases 1 (1985-1988), 2 (1989-1990) and 3 (1991-1993). Cognitive performance was assessed at phases 5 (1997-1999) and 7 (2003-2004) using the following tests: verbal memory, inductive reasoning (Alice Heim), verbal meaning (Mill Hill), phonemic and semantic fluency. Analyses were adjusted for age, sex and employment grade. RESULTS: Longer exposure to high job strain and shorter exposure to active jobs were associated with lower scores in most of the cognitive performance tests. However, these associations disappeared on adjustment for employment grade. Phonemic fluency was an exception to this pattern. Associations between exposure to an active job and phonemic fluency at both follow-up phases were robust to adjustment for employment grade. However, there was no association between exposure to active jobs and change in phonemic fluency score between the follow-up phases after adjustment for employment grade. CONCLUSIONS: In these data, associations between cumulative exposure to high-strain or active jobs and cognition are largely explained by socioeconomic position.

Obesity and overweight in relation to liver disease mortality in men: 38 year follow-up of the original Whitehall study.

Obesity has been implicated in the aetiology of liver disease. However, to date, evidence is largely drawn from cross-sectional studies, where interpretation is hampered by reverse causality, and from studies on clinical populations that have limited generalisability. In this prospective cohort study, data on body mass index (BMI) and covariates were collected at baseline on 18 863 male government employees (aged 40-69 years). Respondents were then followed up for a maximum of 38 years of age. Mortality surveillance gave rise to 13 129 deaths, 122 of which were due to liver disease (57 cancers; 65 non-cancers). In age-adjusted analyses, BMI was positively related to total liver disease mortality (hazards ratio per 1 s.d. increase in BMI; 95% confidence interval (CI): 1.36; 1.14, 1.62) in a graded fashion across the weight categories (P-value for trend: 0.01). The magnitude of this association was somewhat stronger for non-cancer liver disease deaths (1.47; 1.16, 1.86) than for cancer liver disease deaths (1.25; 0.96, 1.62). Excluding deaths in the first 10 years of follow-up somewhat strengthened the BMI-non-cancer liver disease association. Adjustment for socioeconomic position, other candidate confounders and mediating factors led to the modest attenuation of these associations. Further investigation in prospective cohort studies with more detailed data on liver disease, for instance using biochemical tests of liver function or hepatic ultrasonography, is warranted.

Biological and behavioural explanations of social inequalities in coronary heart disease: the Whitehall II study.

AIMS/HYPOTHESIS: We determined the degree to which metabolic syndrome components, inflammation and health behaviours account for the social gradient in CHD. METHODS: A total of 5312 men, initially aged 39 to 63 years, were followed for 13.1 years for incident coronary death or non-fatal myocardial infarction according to socioeconomic position (employment grade). The contribution of explanatory factors to socioeconomic differences in CHD was assessed by the reduction in hazard ratios computed using Cox models. The effects of measurement error were taken into account. RESULTS: Coronary events were more common in lower employment grades than in higher, with a hazard ratio (relative index of inequality) of 2.2 (95% CI 1.3-3.7), after adjustment for age and ethnic group. Behavioural risk factors (mainly smoking and diet) explained a third of the socioeconomic gradient in CHD incidence. Components of the metabolic syndrome and inflammatory markers predicted CHD incidence and also explained a third of the gradient. Combined, these two groups of predictors, i.e. behavioural and biological, accounted for over half of the socioeconomic gradient in incident CHD. Adding body height as a marker of the effects of early life increased this figure to about 60%. CONCLUSIONS/INTERPRETATION: A major question has been how someone's socioeconomic position can lead to increased risk of CHD. Socioeconomic differences in components of the metabolic syndrome (and inflammatory markers) provide part of the answer. This was, to an important degree, independent of the contribution of health behaviours to the socioeconomic differentials in CHD.