Results

Table 1 shows the distribution of father's social class, height and own education according to current employment grade at the time of the phase 1 examination of the Whitehall II cohort. As anticipated there were associations between current and early life social status and height. The relation between grade and father's social class was stronger in women. The relation between father's social class and height (not shown) could all be “explained” by the relation between grade and height.

Table 2, for men, shows the relation to three disease end points of current grade, father's social class, height and age at leaving full time education. There was a monotonic association between grade of employment, but not participant's own education, and incidence of CHD, chronic bronchitis and depression. Father's social class was not significantly related to CHD or bronchitis but was positively related to depression. The tallest men had the lowest incidence of CHD and the trend, shorter height higher disease, was statistically significant. This relation was independent of employment grade. Height was not related to chronic bronchitis or depression.

Table 3, shows the same analyses for women. As with men, there was a graded inverse association between grade of employment and CHD. The relation between grade and chronic bronchitis was in the same direction but the trend was not statistically significant. There was no relation between grade and depression, but more highly educated women were more at risk of depression. There were no significant relations between parental variables and CHD although there was a suggestion that father's social class was related to CHD incidence. Surprisingly, women whose fathers were of lower social class had lower incidence of chronic bronchitis and depression

Comparisons of the independent effects on morbidity of father's social class, employment grade when entering the civil service, and employment grade at phase 1 of the Whitehall II study are shown in table 4. For men, father's social class was not an independent predictor of CHD or chronic bronchitis. For women, there was an association (non-significant) between father's social class and CHD. Interestingly, both first grade and current grade seem to make some contribution to prediction of CHD and, in men, chronic bronchitis. In contrast, among men, first grade and father's social class were positively associated with the onset of depression.

Table 5 shows that among the group with “long lived” parents, grade of employment continues to predict all three end points in men and CHD in women. In women, grade only predicted chronic bronchitis if at least one parent died “prematurely”. The percentage of participants in whom either parent died prematurely varied little by sex or among the three measures of morbidity (ranging from 47.4% (2695 of 5680) to 52.7% (1406 of 2669)). The age adjusted rates of each morbidity comparing those with, to those without death of either parent aged under 70 years, was different from unity only for chronic bronchitis in women (rate ratio 1.37 (95CI% 1.0, 1.8)).

Discussion

In the Whitehall II study, current socioeconomic status in adulthood, rather than father's social class, predicted adult morbidity from CHD, chronic bronchitis and depression. This finding may be considered in the context of three different ways in which factors from early life might influence subsequent disease risk. The first is a latency model. Barker's findings are consistent with this, showing a clear association between low birth weight or thinness at birth and subsequent cardiovascular disease.19 Although size at birth is linked to social circumstances, his studies report effects on coronary risk independent of social class. A second model is cumulation of advantage and disadvantage through the lifecourse.20-22 Studies that have examined social circumstances in childhood and beyond do show an effect on blood pressure, obesity (Wadsworth et al, unpublished data) and measures of health status.22 A third model is the pathway model23 in which childhood circumstances may not affect adult risk directly. As our analyses of inter-generational occupational mobility show, childhood circumstances determine adult circumstances and these, in turn, affect disease risk.

Studies that have examined the effects of social circumstances at different stages of the life course in relation to cardiovascular disease present a mixed picture.24 Consistent with the Whitehall II findings, the Kuopio study of men born 1934–52 showed no childhood effect after adjustment for adult socioeconomic position.13 By contrast, in a Swedish cohort,25 born 1946–55, where it is reasonable to speculate that socioeconomic conditions would have been more favourable than at the time of birth of the Kuopio cohort in east Finland, childhood socioeconomic factors did seem to have an independent effect on CHD risk. The west of Scotland cohort, born in the early part of the century, found substantial childhood effects additional to, and independent of those associated with adult social position.26 In the British Regional Heart Study of men born 1919–38, there was no childhood social class effect on myocardial infarction in men who were themselves in manual occupations; there was an effect among men in non-manual occupations.27 The Nurses Health study showed a modest effect of father's occupation on risk of coronary disease. The effect may have been small because in this cohort of nurses adult occupation was relatively homogeneous.28

What might explain the weaker effects of father's social class than current socioeconomic status in Whitehall II and the discrepancy with the findings of other studies? Firstly, the result in Whitehall II might arise if there were a lack of civil servants with disadvantaged parents. While it is true that there are fewer Whitehall II participants with fathers from a manual background than in the general population, the numbers are large enough to detect effects if present (the proportions from a manual background in Whitehall II compared with the 1946 birth cohort were: men 41.4% versus 74.0% and women 51.5% versus 74.6%). Furthermore, the absence of Whitehall II participants in manual classes may be less significant in the 1980s and 1990s than previously because of changes in British occupational structure. Manual work has declined and unskilled non-manual work with low decision authority and low wages has expanded. In these terms29clerical and other support staff in the civil service are a group at considerable social disadvantage.

Precision of measurement of socioeconomic status provides a second possible explanation for the lack of early life effects observed in Whitehall II. Adult socioeconomic status based on civil service employment grade may be more precisely measured than parental socioeconomic status based on recall of occupation coded into registrar general's social class. The validity of the registrar general classification has been questionned and is currently being replaced. Civil service employment grade by contrast captures aspects of work and social life more strongly related to a broad range of health outcomes. However, other studies have used recalled father's registrar general's social class and find early life effects. In Whitehall II, father's social class was not clearly associated with adult morbidity in univariate or multivariate analyses.

Employment grade may partly capture aspects of parental socioeconomic status, indeed current grade was strongly related to father's social class. In this population, the importance of social circumstances early in life may be in the way they influence employment and social position and thus exposures in adult life. Consistent with this are the results of an analysis with participants cross classified by grade (high versus low) and father's social class (high versus low). Only 107 men were in the downwardly mobile group. Of the high grade men, 1186 of 2953 came from low social class. Their heart disease rate was the same as that of high grade men with advantaged background but lower than that of low grade men. Similar results were found for women.

The finding on parents' age at death is perhaps the strongest argument against a parental disadvantage (either social or genetic) explanation of socioeconomic inequalities in health. If parents survive beyond the age of 70, they could be thought of as neither genetically nor environmentally predisposed to illness. The fact that the social gradient holds up in this subgroup points to the effect of current social circumstances. The main exception was for chronic bronchitis in women where an effect of grade was evident only in “susceptibles”—that is, those with a parent who had died prematurely.

We predicted that, if anything, father's social class would be a stronger predictor of adult morbidity in women. Women's social standing may be more persistently influenced by their family background, especially if there is a “glass ceiling” limiting women's promotion chances.30 Support for this view is in table 1, which shows that of the high grade men 48% had fathers in social class I and II; the figure for women was 69%. Coming from an advantaged background has a bigger effect on achieved employment grade in women than men. Furthermore, smoking among adult women was more common among those whose father's were in manual social class.5 It was surprising therefore to find that chronic bronchitis and depression in women was more frequent among those with higher social class fathers. This may reflect the pressures on women of higher status being greater than among men. This is an area of further inquiry in the Whitehall II study. Alternatively, there may be differential selection effects by grade of employment in women: depression could be a bigger barrier to employment in low status than in high status women. Only five women whose father's were in social class IV or V had chronic bronchitis making the estimate of this effect unstable.

Although the cumulation model may apply in other circumstances, it is the latency and pathway models that would seem to find most support in these Whitehall II findings.

The significant relation between short height and coronary risk, independent of grade of employment, is consistent with a long term effect of early life—a latency model. The pathway model suggests that early social circumstances influence grade at entry to the civil service and promotion to current grade. Height could also play a part in influencing promotion chances and hence be part of a pathway process. These in turn reflect current social circumstances that account for the socioeconomic differences in our three end points.

The findings on depression raise the question of depression affecting social mobility. Men and women whose fathers were of higher social class were at higher risk of depression. Similarly, high grade at entry to the civil service was predictive of depression, in contrast with “current” grade where low grade predicted depression. If “incident” depression in people who were not depressed at baseline were, in fact, a recurrence of depressive symptoms in people with a long history, an explanation of these findings is that depression retarded promotion in the civil service. This is consistent with findings on mobility in the first five years of Whitehall II.31

This explanation could not apply to CHD. Low starting grade is associated with increased CHD risk. This would be predicted by a pathway model in which general social advantage facilitated entry into the civil service at a high level and was associated with lower CHD risk.32 Lower current grade is thus reflective of current circumstances, including power relations in the workplace that are related to CHD.32

Although the instruments used to assess the disease end points have been validated, such self report measures may entail some social class bias.33 These cannot explain the relations between grade of employment and the three diseases as an array of other analyses show similar findings.34 It is not obvious why social class bias in reporting disease should weaken associations with social class of background. Nevertheless as “harder” end points accumulate, these findings can be further tested.

The findings reported here in relation to disease end points from Whitehall II are consistent with our previous analysis of cardiovascular risk factors in this cohort.5 In men, smoking, physical inactivity and a range of metabolic risk factors are primarily associated with current employment grade and not with father's social class. Obesity was linked both to current employment grade and father's social class. These risk factor findings are similar to those previously reported from Scotland.21

In a prospective study of over 7000 civil servants we found that incident adult morbidity was more strongly related to adult employment grade than father's social class. These findings are consistent with a “pathway” interpretation. This emphasises the importance for policy addressing early life disadvantage11 in this case because it influences adult circumstances rather than influencing disease directly. A further implication for policy is that improvement in the conditions in which adults live and work is likely to improve disease risk independent of earlier disadvantage.