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.

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.

Socioeconomic gradients in cardiorespiratory disease and diabetes in the 1960s: baseline findings from the GPO study.

OBJECTIVES: To describe the socioeconomic distribution of risk factors for cardiorespiratory disease and diabetes in employed women and men in the late 1960s. STUDY DESIGN AND METHODS: Cross-sectional data were collected from 3345 General Post Office (GPO) employees in London, via a questionnaire and clinical examination, between October 1966 and April 1967. RESULTS: Our occupational grade classification conformed to expected patterns of greater car ownership and gardening among higher-grade women and men, and greater height in higher-grade men (highest-lowest grade 175.0-170.7 cm, P<0.001). A strong inverse grade gradient in bronchitis (2.1-9.4%, P<0.001) and a strong positive gradient in FEV1 (3.10-2.58l, P<0.001) were observed in men, although smoking was less consistently associated with grade. There was no consistent inverse association between grade and any cardiovascular risk factor in either sex, but strong inverse gradients in prevalence of impaired glucose tolerance (IGT) (5.1-18.2%, P<0.001) and 2-h glucose (4.14-4.25 mmol/l, P<0.001) in non-diabetic men. Using car ownership as an alternative measure of socioeconomic position, findings in men were replicated for respiratory measures, IGT and 2-h glucose prevalence. Inverse gradients were additionally observed for blood pressure, cholesterol and electrocardiogram abnormalities. CONCLUSIONS: The GPO study confirms existing evidence of socioeconomic gradients in respiratory risk factors and provides new evidence of gradients in risk factors for diabetes in men. Although there was no conclusive evidence of an occupational gradient in any cardiovascular risk factor, car ownership was a good indicator of lower risk in men. No socioeconomic gradients in cardiorespiratory or diabetic risk factors were observed in women.

Self-reported economic difficulties and coronary events in men: evidence from the Whitehall II study.

BACKGROUND: Numerous studies have demonstrated social inequalities in coronary heart disease using a variety of measures of social position. In this study we examine associations between persistent economic difficulties and serious coronary events. Our aim is to assess whether these associations are (i) explained by other measures of socioeconomic status, and (ii) mediated by psychosocial, behavioural and biological factors. METHODS: The data come from 5021 middle-aged, white-collar men in the Whitehall II study. Self-reported household financial problems, measured at baseline (1985-88) and Phase 3 (1991-93), were used to construct a five-category score of persistent economic difficulties. Associations between economic difficulties and incident coronary events were determined over an average follow-up of 7 years. Other socioeconomic, psychosocial, behavioural and biological explanatory variables were obtained from the Phase 3 questionnaire and clinical examination. RESULTS: Age-adjusted Cox regression analyses demonstrated steep gradients in the incidence of coronary events with economic difficulties. The relative hazard between the bottom and the top of the difficulties hierarchy was 2.5 (95% confidence intervals (CI) 1.2-5.2) for fatal and non-fatal myocardial infarction (MI), 2.1 (1.3-3.6) for MI plus definite angina and 2.8 (1.9-4.2) for total coronary events. Adjustment for other markers of socioeconomic position, early life factors, psychosocial work environment characteristics and health-related behaviours had little effect, while adjustment for the biological factors reduced the association between difficulties and coronary events by 16-24%. CONCLUSION: We have demonstrated an economic difficulties gradient in coronary events in men that is independent of other markers of socioeconomic position and appears to be only partially mediated by well-known risk factors in mid-life.

Change in health inequalities among British civil servants: the Whitehall II study.

STUDY OBJECTIVE: Despite an overall decline in mortality rates, the social gradient in mortality has increased over the past two decades. However, evidence on trends in morbidity and cardiovascular risk factors indicates that socioeconomic differences are static or narrowing. The objective of this study was to investigate morbidity and cardiovascular risk factor trends in white collar British civil servants. DESIGN: Self rated health, longstanding illness, minor psychiatric morbidity (General Health Questionnaire (GHQ) 30 score, GHQ caseness and GHQ depression subscale), cholesterol, diastolic and systolic blood pressure, body mass index, alcohol over the recommended limits, and smoking were collected at baseline screening (1985-88) and twice during follow up (mean length of follow up 5.3 and 11.1 years). Employment grade gradients in these measures at each phase were compared. SETTING: Whitehall II, prospective cohort study. PARTICIPANTS: White collar women and men aged 35-55, employed in 20 departments at baseline screening. Analyses included 6770 participants who responded to all three phases. RESULTS: Steep employment grade gradients were observed for most measures at second follow up. In general, there was little evidence that employment grade gradients have increased over the 11.1 years of follow up, but marked increases in the gradient were observed for GHQ score (p<0.001) and depression (p=0.05) in both sexes and for cholesterol in men (p=0.01). CONCLUSIONS: There is little evidence of an increase in inequality for most measures of morbidity and cardiovascular risk factors in white collar civil servants over the 11.1 years to 1998. Inequalities have increased significantly for minor psychiatric morbidity in both sexes and for cholesterol in men.

Socioeconomic position, health, and possible explanations: a tale of two cohorts.

OBJECTIVES: We examined whether the social gradient for measures of morbidity is comparable in English and French public employees and investigated risk factors that may explain this gradient. METHODS: This longitudinal study of 2 occupational cohorts-5825 London civil servants and 6818 French office-based employees-used 2 health outcomes: long spells of sickness absence during a 4-year follow-up and self-reported health. RESULTS: Strong social gradients in health were observed in both cohorts. Health behaviors showed different relations with socioeconomic position in the 2 samples. Psychosocial work characteristics showed strong gradients in both cohorts. Cohort-specific significant risk factors explained between 12% and 56% of the gradient in sickness absence and self-reported health. CONCLUSIONS: Our cross-cultural comparison suggests that some common susceptibility may underlie the social gradient in health and disease, which explains why inequalities occur in cultures with different patterns of morbidity and mortality.

Do socioeconomic disadvantages persist into old age? Self-reported morbidity in a 29-year follow-up of the Whitehall Study.

OBJECTIVES: This study examined (1) the relation of employment grade in middle age to self-reported poor health and functional limitations in old age and (2) whether socioeconomic status at approximately the time of retirement modifies health differentials in old age. METHODS: Survivors of the Whitehall Study cohort of men were resurveyed. Respondents were aged 40 to 69 years when they were originally screened in 1967 to 1970. RESULTS: Compared with senior administrators, men in clerical or manual (low-grade) jobs in middle age had quadruple the odds of poor physical performance in old age, triple the odds of poor general health, and double the odds of poor mental health and disability. At most, 20% of these differences were explained by baseline health or risk factors. Men who moved from low to middle grades before retirement were less likely than those who remained in low grades to have poor mental health. CONCLUSIONS: Socioeconomic status in middle age and at approximately retirement age is associated with morbidity in old age.

Employment grade differences in cause specific mortality. A 25 year follow up of civil servants from the first Whitehall study.

STUDY OBJECTIVE: To test the hypothesis that the association between socioeconomic status and mortality rates cuts across the major causes of death for middle aged and elderly men. DESIGN: 25 year follow up of mortality in relation to employment grade. SETTING: The first Whitehall study. PARTICIPANTS: 18,001 male civil servants aged 40-69 years who attended the initial screening between 1967 and 1970 and were followed up for at least 25 years. MAIN OUTCOME MEASURE: Specific causes of death. RESULTS: After more than 25 years of follow up of civil servants, aged 40-69 years at entry to the study, employment grade differences still exist in total mortality and for nearly all specific causes of death. Main risk factors (cholesterol, smoking, systolic blood pressure, glucose intolerance and diabetes) could only explain one third of this gradient. Comparing the older retired group with the younger pre-retirement group, the differentials in mortality remained but were less pronounced. The largest decline was seen for chronic bronchitis, gastrointestinal diseases and genitourinary diseases. CONCLUSIONS: Differentials in mortality persist at older ages for almost all causes of death.

When does cardiovascular risk start? Past and present socioeconomic circumstances and risk factors in adulthood.

STUDY OBJECTIVES: To compare associations of childhood and adult socioeconomic position with cardiovascular risk factors measured in adulthood. To estimate the effects of adult socioeconomic position after adjustment for childhood circumstances. DESIGN: Cross sectional survey, using the relative index of inequality method to compare socioeconomic differences at different life stages. SETTING: The Whitehall II longitudinal study of men and women employed in London offices of the Civil Service at study baseline in 1985-88. PARTICIPANTS: 4774 men and 2206 women born in the period 1930-53 who were administered questions on early socioeconomic circumstances. MAIN RESULTS: Adult occupational position (employment grade) was inversely associated (high status-low risk) with current smoking and leisure time physical inactivity, with waist/height, and with metabolic risk factors HDL cholesterol, triglycerides, post-load glucose and fibrinogen. Associations of these variables with childhood socioeconomic position (father's Registrar General Social Class) were weaker or absent, with the exception of smoking in women. Childhood social position was associated with adult weight in both sexes and with current smoking, waist/height, HDL cholesterol and fibrinogen in women. Height, a measure of health capital or constitution, was weakly linked with father's social class and more strongly linked with own employment grade. The combination of childhood disadvantage (low father's class) together with a low status clerical occupation in men was particularly associated with higher body mass index as an adult (interaction test p < 0.001). Adjustment for earlier socioeconomic position--using father's class and own education level simultaneously--did not weaken the effects of adult socioeconomic position, except in the case of smoking in women, when the grade effect was reduced by 59 per cent. CONCLUSIONS: Cardiovascular risk factors in adulthood were in general more strongly related to adult than to childhood socioeconomic position. Among women but not men there was a strong but unexplained link between father's class and adult smoking habit. In both sexes degree of obesity was associated with both childhood and adulthood social position. These findings suggest that the socially patterned accumulation of health capital and cardiovascular risk begins in childhood and continues, according to socioeconomic position, during adulthood.

Social inequality in coronary risk: central obesity and the metabolic syndrome. Evidence from the Whitehall II study.

This report describes the social distribution of central obesity and the metabolic syndrome at the Whitehall II study phase 3 examination, and assesses the contribution of health related behaviours to their distribution. Cross-sectional analyses were conducted utilising data collected in 1991-1993 from 4978 men and 2035 women aged 39-63 years who completed an oral glucose tolerance test. There was an inverse social gradient in prevalence of the metabolic syndrome. The odds ratio (95% confidence interval) for having the metabolic syndrome comparing lowest with highest employment grade was: men 2.2 (1.6-2.9), women 2.8 (1.6-4.8). Odds ratios for occupying the top quintile of the following variables, comparing lowest with highest grade, were, for waist-hip ratio: men 2.2 (1.8-2.8), women 1.6 (1.1-2.4); post-load glucose: men 1.4 (1.1-1.8), women 1.8 (1.2-2.6); triglycerides: men 1.6 (1.2-2.0), women 2.2 (1.5-3.3); fibrinogen: men 1.7 (1.4-2.3), women 1.9 (1.2-2.8). Current smoking status, alcohol consumption and exercise level made a small contribution (men 11%, women 9%) to the inverse association between socioeconomic status and metabolic syndrome prevalence. In conclusion, central obesity, components of the metabolic syndrome and plasma fibrinogen are strongly and inversely associated with socioeconomic status. Our findings suggest the metabolic syndrome may contribute to the biological explanation of social inequalities in coronary risk. Health related behaviours appear to account for little of the social patterning of metabolic syndrome prevalence.

The relationship between socioeconomic status, hostility, and blood pressure reactions to mental stress in men: data from the Whitehall II study.

This study investigated the relationship among blood pressure reactions to mental stress, cynical hostility, and socioeconomic status (SES) in 1,091 male public servants. Occupational grade served to index SES and cynical hostility was assessed using the Cook-Medley scale. (Cook & Medley, 1954). The magnitude of systolic, but not diastolic, blood pressure change scores to stress was positively associated with occupational grade: the higher the grade, the greater the reactions. Mental stress task performance also varied with occupational grade but was unrelated to reactivity. Ratings of task difficulty did not vary with occupational grade. Cynical hostility was negatively related to occupational grade, and, contrary to previous findings, negatively related to systolic blood pressure reactivity. Cynical hostility was also negatively related to mental stress task performance but unrelated to ratings of task difficulty.

Do socioeconomic differences in mortality persist after retirement? 25 year follow up of civil servants from the first Whitehall study.

OBJECTIVE: To assess the risk of death associated with work based and non-work based measures of socioeconomic status before and after retirement age. DESIGN: Follow up study of mortality in relation to employment grade and car ownership over 25 years. SETTING: The first Whitehall study. SUBJECTS: 18,133 male civil servants aged 40-69 years who attended a screening examination between 1967 and 1970. MAIN OUTCOME MEASURE: Death. RESULTS: Grade of employment was a strong predictor of mortality before retirement. For men dying at ages 40-64 the lowest employment grade had 3.12 times the mortality of the highest grade (95% confidence interval 2.4 to 4.1). After retirement the ability of grade to predict mortality declined (rate ratio 1.86; 1.6 to 2.2). A non-work based measure of socioeconomic status (car ownership) predicted mortality less well than employment grade before retirement but its ability to predict mortality declined less after retirement. Using a relative index of inequality that was sensitive to the distribution among socioeconomic groups showed employment grade and car ownership to have independent associations with mortality that were of equal magnitude after retirement. The absolute difference in death rates between the lowest and highest employment grades increased with age from 12.9 per 1000 person years at ages 40-64 to 38.3 per 1000 at ages 70-89. CONCLUSIONS: Socioeconomic differences in mortality persist beyond retirement age and in magnitude increase with age. Social differentials in mortality based on an occupational status measure seem to decrease to a greater degree after retirement than those based on a non-work measure. This suggests that alongside other socioeconomic factors work itself may play an important part in generating social inequalities in health in men of working age.

The assessment of biological age: a report from the Department of Environment Study.

Indicators of ageing were measured in 397 male and 130 female London Civil Servants aged from 37 to 58 years of age. Grey hair, skin inelasticity, and arcus senilis were strongly and independently related to chronological age. Also independently related were serum albumin (negatively related in both sexes), baldness, serum creatinine, systolic blood pressure, serum calcium (negatively) and ESR in men, and serum cholesterol in women. Chronological age was regressed on the above variables for men and women separately to provide regression equations. Biological age for an individual was calculated by entering his or her results and calculating the residuals. Biological age in those who stopped smoking tended to be younger than chronological age by an average of 12-13 months in men and 1-4 months in women. Men and women who had never smoked had higher biological than actual ages but not after adjusting for regression dilution bias. Men who currently smoked had higher biological ages of 2-3 months but not women smokers (4-6 months lower). Similarly, men of lower employment grades had an average biological age 13 months older and women 8 months, compared with higher employment grades. These differences between employment grade appeared to be due to ESR, arcus senilis, systolic blood pressure and serum cholesterol. These four measurements may be markers of biological rather than chronological age, and the value of attempting to measure biological age is discussed.

Explaining socioeconomic differences in sickness absence: the Whitehall II Study.

OBJECTIVE: To describe and explain the socioeconomic gradient in sickness absence. DESIGN: Analysis of questionnaire and sickness absence data collected from the first phase of the Whitehall II study. Grade of employment was used as a measure of socioeconomic status. SETTING: 20 civil service departments in London. SUBJECTS: 6900 male and 3414 female civil servants aged 35-55 years. MAIN OUTCOME MEASURES: Rates of short spells (< or = 7 days) and long spells (> 7 days) of sickness absence. RESULTS: A strong inverse relation between grade of employment and sickness absence was evident. Men in the lowest grade had rates of short and long spells of absence 6.1 (95% confidence interval 5.3 to 6.9) and 6.1 (4.8 to 7.9) times higher than those in the highest grade. For women the corresponding rate ratios were 3.0 (2.3 to 3.9) and 4.2 (2.5 to 6.8) respectively. Several risk factors were identified, including health related behaviours (smoking and frequent alcohol consumption), work characteristics (low levels of control, variety and use of skills, work pace, and support at work), low levels of job satisfaction, and adverse social circumstances outside work (financial difficulties and negative support). These risk factors accounted for about one third of the grade differences in sickness absence. CONCLUSION: Large grade differences in sickness absence parallel socioeconomic differences in morbidity and mortality found in other studies. Identified risk factors accounted for a small proportion of the grade differences in sickness absence. More accurate measurement of the risk factors may explain some of the remaining differences in sickness absence but other factors, as yet unrecognised, are likely to be important.

The assessment of the relationship between blood pressure and sodium intake using whole-day, daytime and overnight urine collections.

The usefulness of whole-day, daytime (waking to retiring time) and overnight urine samples for assessing the relationship between blood pressure and sodium intake was examined in 301 male London civil servants, aged from 37 to 58 years old. Systolic blood pressure (SBP)/diastolic blood pressure (DBP) averaged 126/78 mmHg and the 24-h urinary excretion of sodium and potassium was 174 and 73 mmol, respectively. There was poor consistency between day- and night-time urine samples with respect to both sodium and potassium content. The urinary excretion of sodium and potassium was lower (P less than 0.001) in overnight than in daytime samples. After standardization for creatinine, the night: day ratio was 0.79 for sodium output and 0.55 for potassium excretion. Blood pressure, adjusted for age and body mass index, was significantly and positively correlated with overnight sodium excretion (SBP/DBP: slope = 0.061/0.046 mmHg/mmol) whereas the correlations with sodium excretion in daytime (0.010/0.004 mmHg/mmol) and whole-day (0.024/0.016 mmHg/mmol) urine samples were not significant. Blood pressure was significantly correlated with the sodium:potassium ratio in whole-day urine (1.941/1.968 mmHg/unit). As the agreement between daytime and overnight urine samples was low with respect to both sodium and potassium content, and due to the fact that the relationship between blood pressure and sodium in overnight samples may at least partially reflect pressure diuresis, overnight urinary sodium, even if related to sodium intake, cannot be employed to assess the association between salt in the diet and blood pressure.

Confounding of occupation and smoking: its magnitude and consequences.

In a recent contribution to this journal, Sterling and Weinkam discuss the importance of the confounding of occupation and smoking when considering the contribution of smoking to mortality risk. In this report we provide estimates of the potential magnitude of this effect using data from a cohort study. It is shown that failing to consider possible confounding by socio-economic factors can lead to over-estimating of the strength of the relationship between smoking and mortality. The implications of these findings for the interpretation of results derived from observational studies are discussed.

Magnitude and causes of socioeconomic differentials in mortality: further evidence from the Whitehall Study.

STUDY OBJECTIVE: The aim was to explore the magnitude and causes of the differences in mortality rates according to socioeconomic position in a cohort of civil servants. DESIGN: This was a prospective observational study of civil servants followed up for 10 years after baseline data collection. SETTING: Civil service offices in London. PARTICIPANTS: 11,678 male civil servants were studied, aged 40-64 at baseline screening between 1967 and 1969. Two indices of socioeconomic position were available on these participants--employment grade (categorised into four levels), and ownership of a car. MEASUREMENTS AND MAIN RESULTS: Main outcome measures were all cause and cause specific mortality, with cause of death taken from death certificates coded according to the eighth revision of the ICD. Employment grade and car ownership were independently related to total mortality and to mortality from the major cause groups. Combining the indices further improved definition of mortality risk and the age adjusted relative rate between the highest grade car owners and the lowest grade non-owners of 4.3 is considerably larger than the social class differentials seen in the British population. Factors potentially involved in the production of these mortality differentials were examined. Smoking, plasma cholesterol concentration, blood pressure, and glucose intolerance did not appear to account for them. The pattern of differentials was the same in the group who reported no ill health at baseline as it was in the whole sample, which suggests that health selection associated with frank illness was not a major determinant. The contribution of height, a marker for environmental factors acting in early life, was also investigated. Whereas adjustment for employment grade and car ownership attenuated the association between short stature and mortality, height differences within employment grade and car ownership groups explained little of the differential mortality. CONCLUSION: The use of social class as an index of socioeconomic position leads to underestimation of the association between social factors and mortality, which may be reflected in public health initiatives and priorities. Known risk factors could not be shown to account for the differentials in mortality, although the degree to which this can be explored with single measurements is limited.

Fibrinogen: a possible link between social class and coronary heart disease.

Mortality from coronary heart disease in civil servants in the lowest grade of employment has been found to be about three times that of men in the highest grade of employment. As part of an investigation of this finding several haemostatic variables were measured in a sample of 29 men in lower grades of employment and 45 men in higher grades. There was a significant difference in plasma fibrinogen concentrations between men in lower grades of employment and those in higher grades (mean 3.39 g/l v 2.95 g/l, respectively; p less than 0.01) but not in other haemostatic variables. Multiple regression analyses showed significant independent associations of fibrinogen concentration with smoking (p less than 0.05) and grade of employment (p less than 0.05). The size of the observed difference between the grades of employment was similar to that between those dying of coronary heart disease or surviving during longitudinal study; it may therefore be an important part of the mechanism underlying social class differences in coronary heart disease. The statistical relation between fibrinogen concentrations and other characteristics that may be concerned in the aetiology of coronary heart disease was examined. A summary measure of job stress was significantly related to fibrinogen concentration (p less than 0.01) and made a substantial contribution to explaining the differences between grades of employment. Behaviour type and a score of physical activity were not significantly related to fibrinogen concentration.

Inequalities in death--specific explanations of a general pattern?

In the Whitehall study, 17 530 civil servants were classified according to employment grade, and their mortality was recorded over 10 years. There was a steep inverse relation between grade and mortality. Compared with the highest grade (administrators), men in the lowest grade had 3 times the mortality rate from coronary heart disease, from a range of other causes, and from all causes combined. This is larger than the mortality differences, nationally, between classes I and V. Smoking and other coronary risk factors are more common in the lowest grades, but these differences account for only part of the mortality difference. The similarity of the risk gradient from a range of specific diseases could indicate the operation of factors affecting general susceptibility. The inverse relation between height and mortality suggests that factors operating from early life may influence adult death rates.