Abstract:
Background: Many low- and middle-income countries are facing a double burden of
disease with persisting high levels of infectious disease, and an increasing prevalence of
non-communicable disease (NCD). Within these settings, complex processes and
transitions concerning health and population are underway, altering population dynamics
and patterns of disease. Understanding the mechanisms through which changing
socioeconomic and environmental contexts may influence health is central to developing
appropriate public health policy. Migration, which involves a change in environment and
health exposure, is one such mechanism.
Methods: This study uses Competing Risk Models to examine the relationship between
internal migration and premature mortality from AIDS/TB and NCDs. The analysis
employs 9 to 14 years of longitudinal data from four Health and Demographic
Surveillance Systems (HDSS) of the INDEPTH Network located in Kenya and South
Africa (populations ranging from 71 to 223 thousand). The study tests whether the
mortality of migrants converges to that of non-migrants over the period of observation,
controlling for age, sex and education level.
Results: In all four HDSS, AIDS/TB has a strong influence on overall deaths. However,
in all sites the probability of premature death (45q15) due to AIDS/TB is declining in
recent periods, having exceeded 0.39 in the South African sites and 0.18 in the Kenyan
sites in earlier years. In general, the migration effect presents similar patterns in relation
to both AIDS/TB and NCD mortality, and shows a migrant mortality disadvantage with
no convergence between migrants and non-migrants over the period of observation.
Return migrants to the Agincourt HDSS (South Africa) are on average four times more
likely to die of AIDS/TB or NCDs than are non-migrants. In the Africa Health Research
Institute (South Africa) female return migrants have approximately twice the risk of
dying from AIDS/TB from the year 2004 onwards, while there is a divergence to higher
AIDS/TB mortality risk amongst female migrants to the Nairobi HDSS from 2010.
Conclusion: Results suggest that structural socioeconomic issues, rather than epidemic
dynamics are likely to be associated with differences in mortality risk by migrant status.
Interventions aimed at improving recent migrant's access to treatment may mitigate risk.