It was 1998 when demographer Hans-Peter Kohler first got involved with a research project in rural Malawi. Nearly two decades later, the project, dubbed Malawi Longitudinal Study of Families and Health, which explores the AIDS epidemic, is still in full swing. So is Kohler’s commitment to it.

This past December, Kohler, the Frederick J. Warren Professor of Demography in the School of Arts & Sciences, had research related to his most recent work in Malawi published in the Journal of Health Economics. His findings focused on antiretroviral therapy, or ART, which became widely available in rural Malawi in 2008.

ART treatment allows HIV-positive people to live with the virus without developing AIDS. It also reduces the likelihood of HIV transmission. Before ART, HIV-positive and HIV-negative people alike were giving up hope. Kohler and his team noticed.

“HIV became such a generalized epidemic that people in Malawi, even if they were HIV-negative, became very short-sighted in all of their planning,” Kohler explains. “They didn’t save because they felt there was no point in saving, if they weren’t going to be around to use it later. They weren’t investing in children. But ART reduced this perceived mortality risk.”

After ART came around, it not only improved the lives of those infected with the disease, but also improved the well-being of those without it. There was a significant shift in mindset, as HIV became a much more manageable disease rather than a death sentence.

This information wouldn’t have been as easily understood without the Malawi project, which was spearheaded by Susan Watkins, now a professor emerita at Penn. Since its inception, the project has provided research to produce more than 250 publications and numerous dissertations, and is growing. It’s one of the very few long-standing longitudinal cohort studies in a poor sub-Saharan African context. After Watkins retired a few years ago, Kohler took over as lead investigator.

The researchers have been following a cohort of up to 4,000 individuals, across all adult ages, and have data collection rounds every two or three years. The research team is a collaborative effort between Penn and the University of Malawi, as well as the nonprofit Invest in Knowledge Initiative, which was founded by young Malawians who began working with Kohler and his team in the early 2000s.

“Most of the data collection is just plain old paper and pencil,” says Kohler. “We go out into the field and track the people down, we use GPS coordinates because there are no addresses, and we compare them with pictures to make sure we’re interviewing the right person.”

The Malawi study has been used over the years to document the influence of social networks on HIV-related behaviors and perceptions, HIV prevention strategies, the relationship between life-course transitions and HIV infection risks, the acceptability of HIV testing and counseling, and the health and well-being across the lives of individuals facing multiple challenges resulting from high disease burdens and widespread poverty.

“We’re trying to tell the life story of a group of individuals when the epidemic was on the rise, and now the aftermath,” Kohler says. “We want to keep focusing on them, because it’s interesting how the life of this cohort has unfolded in all dimensions, which is on one hand health, but also the economic, productive, who’s supporting children, how the household looks. It’s a big story we’re trying to tell.”

Next on Kohler’s plate is a conference in Malawi in March, funded by the Economic and Social Research Council, which will explore policy options for the government, donors, and organizations after the peak of the AIDS epidemic. Data from the Malawi project will be showcased to inform decisions about suggested policy changes.

“Making the right policy decisions and interventions is critical because Malawi is clearly a country where resources are scarce, including particularly in the health system and public sector,” Kohler says. “Tradeoffs are very, very real. If you want to invest more in HIV/AIDS, you have to take it from somewhere else.”