Coming home to die? the association between migration and mortality in rural South Africa

BACKGROUND Studies on migration often ignore the health and social impact of migrants returning to their rural communities. Several studies have shown migrants to be particularly susceptible to HIV infection. This paper investigates whether migrants to rural households have a higher risk of dying, especially from HIV, than non-migrants. METHODS Using data from a large and ongoing Demographic Surveillance System, 41,517 adults, enumerated in bi-annual rounds between 2001 and 2005, and aged 18 to 60 years were categorized into four groups: external in-migrants, internal migrants, out-migrants and residents. The risk of dying by migration status was quantified by Cox proportional hazard regression. In a sub-group analysis of 1212 deaths which occurred in 2000 - 2001 and for which cause of death information was available, the relationship between migration status and dying from AIDS was examined in logistic regression. RESULTS In all, 618 deaths were recorded among 7,867 external in-migrants, 255 among 4,403 internal migrants, 310 among 11,476 out-migrants and 1900 deaths were registered among 17,771 residents. External in-migrants were 28% more likely to die than residents [adjusted Hazard Ratio (aHR) = 1.28, P < 0.001, 95% Confidence Interval (CI) (1.16, 1.41)]. In the sub-group analysis, the odds of dying from AIDS was 1.79 [adjusted Odd ratio (aOR) = 1.79, P = 0.009, 95% CI (1.15, 2.78)] for external in-migrants compared to residents; there was no statistically significant difference in AIDS mortality between residents and out-migrants, [aOR = 1.25, P = 0.533, 95% CI (0.62-2.53)]. Independently, females were more likely to die from AIDS than males [aOR = 2.35, P < 0.001, 95% CI (1.79, 3.08)]. CONCLUSION External in-migrants have a higher risk of dying, especially from HIV related causes, than residents, and in areas with substantial migration this needs to be taken into account in evaluating mortality statistics and planning health care services.