Background: Chronic infection with organisms such as Chlamydia pneumoniae is thought to cause coronary heart disease. We investigated whether myocardial infarction deaths are associated with large household size and overcrowding, as these are factors that may facilitate the transmission of infection.
Design: Ecological study of England and Wales.
Methods: Population data were obtained from the 1991 National Census and mortality data were obtained from the Office of National Statistics. For various categories of household size and overcrowding, we calculated mortality rates standardized for age, sex and deprivation.
Results: Standardized mortality rates for acute respiratory infections were associated with household size and overcrowding, while rates for myocardial infarction and gastric carcinoma, both putatively associated with chronic infection, were associated with household size. For combined deaths from causes other than myocardial infarction, there were small associations with household size and overcrowding. In the case of myocardial infarction, the association was generally strongest in the age group 45-54.9 years. For this age group, the standardized mortality rate ratio for the category of largest size household was 2.7 in the year 1991.
Conclusions: There is an association between household size and mortality from myocardial infarction. Chronic infection is a possible cause.