HIV-1 incidence and HIV-1 associated mortality in a cohort of urban factory workers in Tanzania

Abstract

Objective: To determine HIV-1 incidence and HIV-1 associated mortality in a prospective cohort study. To determine whether the cohort is suitable for studies aiming to determine the impact of interventions on HIV-1 incidence.

Methods: The study population was a cohort of 1772 urban factory workers (1478 men and 294 women) in northwest Tanzania. The study took place from October 1991 to September 1993. Outcome measures were HIV-1 seroconversion and death.

Results: HIV-1 incidence was 1.2 (95% CI 0.7-2.0) per 100 person-years (pyr). Crude annual mortality was 4.9 per 100 pyr in those with and 0.3 in those without HIV-1 infection, giving an age and sex adjusted mortality ratio of 12.9 (95% CI 5.4-30.7). Of all deaths, 62% were attributable to HIV-1 infection.

Conclusion: HIV-1 infection was a major public health problem, being the major cause of death in this adult population. At an HIV-1 incidence of 1.2 per 100 pyr, a large cohort size would be required to evaluate the impact of interventions on HIV-1 incidence.

PIP: The objectives were to determine HIV-1 incidence and HIV-1 associated mortality in a prospective cohort study and to determine whether the cohort is suitable for studies attempting to determine the impact of interventions on HIV-1 incidence. The study population was a cohort of 2038 urban factory workers in northwest Tanzania of whom 1772 workers (1478 men or 87% and 294 women or 89%) had enrolled in the study during October 1991 to September 1993. 471 (27%) of the total study population were lost to follow-up by the end of the study period. Outcome measures were HIV-1 seroconversion and death. At intake, 153 of 1478 (10.4%) men and 52 of 294 (17.7%) women were infected with HIV-1. In the study period, 17 seroconversions took place in 1365.9 person years of follow-up giving an HIV-1 incidence rate of 1.2/100 person-years of follow-up. No association was found between seroconversion and age or sex. The crude annual mortality rate was 4.9/100 person-years in those with and 0.3/100 person-years in those without HIV-1 infection, giving an age- and sex-adjusted mortality ratio of 12.9. The age- and sex-adjusted population attributable risk was 0.5/100 person-years, and of all deaths, 62% were attributable to HIV-1 infection. Of the 14 HIV-1 infected people who died, 9 met the criteria of the 1987 revised Centers for Disease Control/World Health Organization AIDS case definition: one had cryptococcal meningitis and eight HIV wasting syndrome. Two others had had weight loss and fever, but the evidence was inadequate to make or reject the diagnosis of AIDS. The remaining three without an AIDS diagnosis had pulmonary tuberculosis, diarrhea, and pyomyositis, respectively. HIV-1 infection was a major cause of death in this adult population. At an HIV-1 incidence of 1.2/100 person-years, a large cohort size would be required to evaluate the impact of interventions on HIV-1 incidence.