Life course determinants of coronary heart disease and stroke in middle-aged Swedish men

Abstract: The general aim of the thesis was to study how socioeconomic and behaviour-related factors measured in childhood, late adolescence or adulthood are related to coronary heart diseae (CHD) and stroke in middle age among Swedish men. The life course approach was central to the aim, and the potential impact of socioeconomic differences in adulthood among the men was considered throughout. The thesis was based on the 1969 conscription cohort, i.e. a cohort of almost 50 000 Swedish men who in 1969/70 went through a conscription examination for compulsory military service. They were between 18 and 20 years of age at that time. Information from physiological assessments, cognitive tests, and questionnaires were used in combination with (1) register-based indicators of social circumstances in childhood and adulthood, and information on educational level, and (2) register-based information on fatal and non-fatal events of CHD and stroke between 1971 and 2007. Multivariable regression methods were used to analyse data. In study I and II, higher levels of BMI and blood pressure in late adolescence were shown to be significantly associated with increased risks of CHD and stroke before 55 years of age. Men with higher BMI were more likely to be in lower socioeconomic positions later in adulthood, but differences among the men in adult socioeconomic positions did not seem to affect, i.e. mediate or modify, associations between BMI/blood pressure in late adolescence and CHD/stroke in middle age. BMI, smoking, and body height in late adolescence were shown, in study III, to contribute to explain associations between childhood socioeconomic position and CHD/stroke in middle age. Possibly, study III also showed that childhood social disadvantage may have an independent long-term effect on CHD and stroke in middle age. In study IV, it was shown that large parts of the associations between educational attainment and CHD/stroke in middle age may be explained by confounding from social and behaviour-related risk factors measured in childhood and late adolescence. Thus, it was shown that factors in childhood and adolescence may be critical in relation to CHD and stroke in middle age among men. Increased risks of CHD and stroke could be an effect of disadvantages in childhood, acting through biological and/or behavioural development early in life. The findings may also be compatible with the view that social disadvantages and adverse behavioural responses from childhood and onwards increase risks of disease, such as CHD and stroke, in a cumulative manner over the life course. Moreover, the findings showed that such accumulation of cardiovascular risk may be most prevalent among men born to parents of lower socioeconomic positions and among men who attain lower educational levels; these are the same categories of men that tend to end up in lower socioeconomic positions in adulthood. In this way, social differences in cardiovascular disease among adult men could possibly be explained by confounding from factors earlier in life.