Prof Kathleen Kahn and Prof Stephen Tollman built South Africa’s most powerful rural population health study from the ground up. What it has revealed about how people age is shaping science and policy far beyond the Lowveld.

Tracy Lee Stark

In 1990, two young researchers joined University of Witwatersrand’s (Wits) Health Systems Development Unit and drove to a cluster of villages in north-eastern South Africa (SA) called Agincourt. They were responding to a gap they could not look past: rural communities, shaped by decades of apartheid-era neglect, had almost no population-based health data. Without that data, health planning was essentially guesswork. With it, evidence for policy could be built from the ground up.

More than 30 years later, what began as an act of principled scientific determination has become one of the world’s most respected long-term population health studies. The SAMRC/Wits Rural Public Health and Health Transitions Research Unit, known as the Agincourt Unit, now follows some 120,000 people in 22,000 households across more than 30 neighbouring villages. It is the only South African Medical Research Council (SAMRC) unit devoted entirely to rural health and development.

The two scientists who built it, Professors Kathleen Kahn and Stephen Tollman, have spent their careers working in close partnership, each bringing distinct scientific leadership to a shared vision.

Prof Kathleen Kahn

Kathy Kahn traces her professional direction to a single formative experience. As a second-year medical student, she participated in an evaluation of voluntary rural women’s groups established to prevent trachoma. The encounter with the lived realities of rural South Africans, and the health inequalities embedded in those realities, set a course from which she has never deviated.

“I have never deviated from undertaking work in the pursuit of greater equity for our country and continent’s most disadvantaged and marginalised communities,” she says.

At the Agincourt Unit, which she co-established with Tollman and where she serves as Principal Scientist, Kahn’s most influential early contribution was establishing and leading the use of verbal autopsy as a systematic way of determining causes of death in places where official death records were limited. In communities where most deaths happen at home rather than in hospitals, this is not simply a research method. It is an essential public health tool. The World Health Organization (WHO) recognised the importance of this work by designating Kahn as Director of its Collaborating Centre for Verbal Autopsy in SA.

Among the most important discoveries was the first evidence that stroke was a leading cause of death among middle-aged and older people in rural SA, occurring just as often as HIV/AIDS among women over 50. The finding changed how researchers and policymakers understood rural health. Communities were carrying a heavy burden of chronic diseases alongside infectious diseases. Integrated healthcare was needed, rather than separate programmes for different illnesses. The research helped motivate the Department of Health (NDoH) to partner with the SAMRC/Wits Agincourt Unit in a national pilot of integrated care.

Kahn also leads the Unit’s adolescent physical and mental health research. Her work on interventions for adolescent depression aims to improve not only mental health outcomes but educational attainment, which Agincourt research has shown is strongly linked to better cognitive health later in life. She co-leads a trial to improve body mass index in underweight and overweight adolescent girls, addressing early-life malnutrition that, if left unchecked, becomes a major driver of Type 2 diabetes in adulthood. More recently, she has turned her attention to HIV prevention in older adults. Her team documented high levels of sexual risk behaviour among people over 40, a population with no targeted prevention programmes. A randomised trial of home-based HIV self-testing found the approach to be safe, preferred by participants, and associated with lower depression scores.

“Healthy ageing begins at early life stages,” she says. “Health is shaped over time, from pre-conception through pregnancy, childhood and adolescence, to older ages.”

The SAMRC/Wits Agincourt Unit employs around 250 people from the study communities each year, many of whom are the sole income earners in their families. Graduate students Kahn supervised are now supervising students of their own. The knowledge generated in Agincourt has also contributed to the Global Burden of Disease 2023 study, coordinated by the Institute for Health Metrics and Evaluation at the University of Washington.

Prof Stephen Tollman

Steve Tollman’s path to Agincourt also began in medical school, and with an encounter with rural apartheid that became defining. Seeing how policy and practice disregarded the rights of rural citizens, he committed himself to work that valued every life and generated evidence capable of changing the conditions shaping that life.

“Passion has several drivers and sources,” he says. “Tackling critical issues and devising solutions that make a difference, especially among middle-aged and older persons who carry tremendous responsibility for children and youth, household and societal development.”

As Director and Research Professor at the SAMRC/Wits Agincourt Unit, Tollman’s career has been built around one central idea: understanding health and ageing in rural SA requires following the same people and communities over many years.

The Agincourt Health and Socio-Demographic Surveillance System, which he co-established with Kahn, does exactly that. One of its most important studies is HAALSA, Health and Ageing in Africa: Longitudinal Studies in SA, which follows around 5,500 people aged 40 and older over time. Running for more than 12 years, it has become one of Africa’s richest sources of information on how HIV, cardiovascular disease, stroke, diabetes, cognitive decline and dementia interact as people age.

The breakthrough Tollman remembers most clearly came as the Unit worked to establish what people were dying from. The discovery that rural women were just as likely to die of stroke as of HIV/AIDS transformed the Unit’s scientific agenda. It paved the way for pioneering work on multiple chronic illnesses, healthy ageing and health systems designed to respond to both.

The platform has since produced evidence that has shaped national policy. Studies documenting dangerously high rates of hypertension contributed to SA’s regulations on the salt content of certain foods, while Agincourt data later showed sustained improvements in sodium intake and blood pressure, particularly among women. An evaluation of the sugar-sweetened beverage tax is now underway. The HAALSA study has also provided real-world evidence of how social grants paid to older people improve the health and wellbeing of entire households.

Technology has played an equally important role in Tollman’s work. The Unit introduced tablet-based cognitive testing to reduce educational and cultural bias in assessing older participants with limited schooling. It developed a system linking research participants with clinic and hospital records, providing a model for future electronic health records in rural public healthcare. It also brought the first portable MRI scanner used in rural Africa to Agincourt, allowing researchers to study brain health and cognitive ageing in communities that had never before had access to this technology. The Unit’s work updating the WHO’s verbal autopsy tools to include COVID-19 is now being evaluated by the WHO and is expected to be widely adopted internationally.

Tollman also played a central role in establishing the South African Population Research Infrastructure Network (SAPRIN), which links population research sites across rural and urban SA. The network will support a national study on healthy ageing in 2026 and 2027, with the Agincourt data collected over three decades providing an important benchmark for the project.

“I am certain that building the evidence to understand and respond to healthy ageing along the life course in the demanding, rapidly changing context of rural SA can make a profound contribution,” he says. “Within SA, on the continent, and across global societies.”

Together

The partnership between Kahn and Tollman is itself a scientific achievement. Reflecting on the Unit’s 25th and later 30th anniversaries, celebrated with staff and alumni at Oxford, Harvard and Wits, they sought to capture not only the scientific and policy advances, but also accounts of the teams they had built, the generations of scientists they had trained, and the long-term relationships with communities without which none of the science would have been possible.

“In Agincourt, no achievement belongs to one person alone,” Kahn says.

“The leadership partnership with Kathleen Kahn is a rare privilege,” Tollman says.

The world now faces an ageing challenge that is as acute in rural SA as it is anywhere else. For more than 30 years, in a cluster of villages in the Lowveld, two scientists quietly built the evidence needed to understand it.

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