The contribution of diet and lifestyle to socioeconomic inequalities in cardiovascular morbidity and mortality☆
Introduction
In many industrialized countries, socioeconomic inequalities in cardiovascular diseases (CVD) have been reported [1], [2]. Cardiovascular morbidity and mortality are higher amongst the lowest socioeconomic groups due to their higher exposure to risk factors, such as low social support, negative life events, unhealthy behaviours, and lower health care utilization [3], [4], [5]. Most studies regarding the mediating role of behaviour on this relationship have focussed on physical inactivity, smoking, alcohol consumption, and obesity [3], [5], [6], [7], [8], [9], [10], [11], [12], [13]. Combinations of these behaviours explained 13% to 60% of the socioeconomic differences in cardiovascular morbidity and 19% to 55% of cardiovascular mortality inequalities.
Evidence is mounting that high socioeconomic position, as defined by high educational level, high income and high occupational class, is consistently associated with healthy dietary patterns such as greater consumption of fruits and vegetables, low-fat dairy products, or whole-grain foods, whereas those with low socioeconomic position tend to consume more meat and fatty foods [14], [15]. Although diet is an important risk factor of CVD [16], little is understood about whether dietary factors, and particularly specific food groups, mediate the impact of socioeconomic status on CVD. The few studies that examined specific dietary intakes showed a relatively small contribution of diet (none to a quarter) to the explanation of socioeconomic inequalities in CVD [4], [17], [18], [19]. This relatively small mediating effect might be the result of not considering overall diet but only some isolated dietary factors, such as frequency of fruit and vegetable consumption, type of bread or milk, and meat, vitamin C, or coffee intake. In addition, most studies, except two [4], [19], focussed on cardiovascular mortality but not morbidity and only one investigated stroke separately [17].
Therefore, the aim of our study was to explore the potential mediating effect of a vast number of dietary factors indicating overall diet and other lifestyle factors on the association between socioeconomic position and coronary heart diseases (CHD) and stroke morbidity and mortality in the Dutch sample of the European Prospective Investigation into Cancer and Nutrition (EPIC-NL), a prospective cohort of 40,011 Dutch men and women.
Section snippets
Study population and design
Between 1993 and 1997, we recruited 17,357 women aged 49–70 years old amongst breast cancer screening participants in the PROSPECT cohort and 22,654 men and women aged 20–59 years, through random population sampling in the MORGEN cohort. These are the two Dutch contributions to the EPIC [20]. The cohorts are described in more detail elsewhere [20]. Both cohorts comply with the Declaration of Helsinki. The subjects gave informed consent. Prospect was approved by the Institutional Review Board of
Results
In total, 2148 subjects acquired cardiovascular disease during follow-up, 1617 with CHD and 531 with stroke (Table 1 in the Supplementary data). The lowest and lower educated groups showed significantly higher risks of CHD (HR = 1.98 (1.67;2.35); HR = 1.50 (1.29;1.75)) and stroke (HR = 1.55 (1.15;2.10); HR = 1.42 (1.08;1.86)) compared with the highest educational level. Unemployed and retired subjects suffered more often from CHD compared to those who were employed (HR = 1.37 (1.19;1.58); HR = 1.20
Discussion
Our results show an educational gradient in CHD and stroke whereas difference between employment status categories was only found for CHD risk. Diet and lifestyle contribute substantially to socioeconomic inequalities in CVD and diet was the most important mediating factor of socioeconomic differences in CHD and stroke. These findings suggest the importance to improve dietary and lifestyle behaviours amongst lower socioeconomic groups not only to improve population health but also to reduce
Conclusion
Our findings indicate that diet, smoking and alcohol consumption largely contributed to socioeconomic inequalities in CVD. Diet accounted for approximately 48% and 67% of educational variation in CHD and stroke risks, and 36% of employment status variation in CHD risk. Our findings indicate that public health interventions that aim to reduce the high prevalence of unhealthy dietary and lifestyle behaviours amongst lower socioeconomic groups may be an effective strategy not only for improving
Acknowledgments
We thank Statistics Netherlands and the PHARMO Institute for follow-up data on vital status and the incidence of non-fatal cardiovascular diseases.
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Source of funding: The EPIC-NL study was supported by the “Europe Against Cancer” Programme of the European Commission; the Dutch Ministry of Public Health, Welfare and Sports; the Dutch Cancer Society; ZonMW the Netherlands Organisation for Health Research and Development; and the World Cancer Research Fund.
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This author takes responsibility for all aspects of the reliability and freedom from bias of the data presented and their discussed interpretation.