Socioeconomic status, pathogen burden and cardiovascular disease risk

Objective

Socioeconomic status (SES) is inversely associated with coronary heart disease (CHD) risk. Cumulative pathogen burden may also predict future CHD. The hypothesis was tested that lower SES is associated with a greater pathogen burden, and that pathogen burden accounts in part for SES differences in cardiovascular risk factors.

Methods

This was a cross‐sectional observational study involving the clinical examination of 451 men and women aged 51–72 without CHD, recruited from the Whitehall II epidemiological cohort. SES was defined by grade of employment, and pathogen burden by summing positive serostatus for Chlamydia pneumoniae, cytomegalovirus and herpes simplex virus 1. Cardiovascular risk factors were also assessed.

Results

Pathogen burden averaged 1.94 (SD) 0.93 in the lower grade group, compared with 1.64 (0.97) and 1.64 (0.93) in the intermediate and higher grade groups (p?=?0.011). Pathogen burden was associated with a higher body mass index, waist/hip ratio, blood pressure and incidence of diabetes. There were SES differences in waist/hip ratio, high‐density lipoprotein‐cholesterol, fasting glucose, glycated haemoglobin, lung function, smoking and diabetes. The SES gradient in these cardiovascular risk factors was unchanged when pathogen burden was taken into account statistically.

Conclusions

Although serological signs of infection with common pathogens are more frequent in lower SES groups, their distribution across the social gradient does not match the linear increases in CHD risk present across higher, intermediate and lower SES groups. Additionally, pathogen burden does not appear to mediate SES differences in cardiovascular risk profiles.There is a socioeconomic gradient in coronary heart disease (CHD) mortality and cardiovascular disease risk in the USA, UK and many other countries.^1,2 Lower socioeconomic status (SES) is associated with a range of cardiovascular risk factors including smoking, adverse lipid profiles, abdominal adiposity, glucose intolerance and inflammatory markers.^3,4,5,6,7 Both early life SES and adult socioeconomic position appear to contribute to the social gradient.^5,8A history of infection may contribute to cardiovascular disease risk by stimulating sustained vascular inflammation. Evidence concerning the relevance of individual pathogens is mixed, but the cumulative pathogen burden, defined by positive serostatus for a range of pathogens, has been associated with coronary artery disease and carotid atherosclerosis in case–control^9,10,11 and longitudinal cohort studies.^12,13,14 Pathogen burden is also related to cardiovascular risk markers such as endothelial dysfunction,¹⁵ low high‐density lipoprotein (HDL)‐cholesterol¹⁶ and insulin resistance,¹⁷ in some but not all studies.^9,18It is plausible that pathogen burden could contribute to SES differences in cardiovascular disease risk. Exposure to infection is greater in lower SES groups, particularly in early life,¹⁹ and childhood infection is associated with endothelial dysfunction.²⁰ We therefore tested the hypothesis that lower SES is associated with greater cumulative pathogen burden in healthy middle‐aged and older adults. Seropositivity was measured for three pathogens, Chlamydia pneumoniae, cytomegalovirus (CMV) and herpes simplex virus 1 (HSV‐1), that have been associated with cardiovascular disease risk,^21,22,23 and have contributed to studies of cumulative pathogen burden.^10,12,14,15 We also determined whether variations in pathogen burden accounted for SES differences in cardiovascular risk factors.