Socioeconomic risk factors for bacterial gastrointestinal infections

Bacterial gastrointestinal infections cause considerable morbidity in industrialized countries, but little is known about socioeconomic factors affecting the risk of infection.

By linkage among 3 national registers, we followed the entire population of Denmark (5.3 million people) from 1993 to 2004 for the occurrence of laboratory-confirmed bacterial gastrointestinal infections. Using Poisson regression analyses, incidence rate ratios (IRRs) were estimated for the major groups of bacteria in different socioeconomic strata, focusing on income group, level of education, marital status, number of children in the household, and country of birth.

Associations with socioeconomic variables varied by type of bacterium. High-income groups had increased risks of infection with Campylobacter, Shigella, and Salmonella Enteritidis, and education was positively associated with increased risk of infection with Campylobacter and Shigella. Married persons were generally at higher risk than single persons, but adults with children had lower risks compared with adults without children. Foreign-born persons generally had lower risks, whereas Danish-born persons with foreign-born parents were at reduced risk of infection with the pork-associated bacterium Yersinia (IRR = 0.33; 95% confidence interval 0.25-0.42), but increased risk with Shigella (5.7; 4.8-6.1), Salmonella, and Shiga toxin-producing Escherichia coli.

The findings suggest that risk of infection is not primarily associated with poverty, but rather with increasing socioeconomic status. Risk of infection also varies with cultural background. Observed differences may be explained by differences in diet and travel activity, although they may also in part reflect differential probabilities of diagnostic reporting.