Effect of a Cash Transfer Intervention on Memory Decline and Dementia Probability in Older Adults in Rural South Africa: An Ancillary Extension to a Phase 3 Randomized Controlled Trial

Background: Evidence on cash transfers as a population-level intervention to support healthy cognitive aging in low-income settings is sparse. We assessed the effect of a cash transfer intervention on longitudinal memory decline and dementia probability in older South African adults. Methods: We leveraged the overlap in the sampling frames of a Phase 3 randomized cash transfer trial (HPTN 068, 2011-2015, NCT01233531) and an aging cohort (HAALSI, 2014-2022) in rural Mpumalanga Province, South Africa. In HPTN 068, young women and their primary caregivers were randomly assigned 1:1 to receive a monthly cash transfer or control. Payments were split between the young woman (1/3) and her caregiver (2/3). In 2014/2015, 862 adults aged 40+ years living in the HPTN 068 trial households were enrolled in the HAALSI cohort, with cognitive outcome data collected in three waves over seven years. We estimated the impact of the intervention on rate of memory decline over seven years and dementia probability scores at endline. Findings: Between March 2011 and December 2012, 862 older adults who would go on to enroll in the HAALSI cohort were living in households enrolled in HPTN 068 and randomized to receive the cash transfer intervention (n=429) or control (n=433). Memory decline in the cash transfer arm was 0.03 SD units (95% CI: 0.002, 0.05) slower per year than in the control arm. Dementia probability scores were 3 percentage points lower in the cash transfer arm than the control arm (b=-0.03; 95% CI: -0.05, -0.001). Effects were consistent across subgroups. Interpretation: A modestly sized household cash transfer delivered over a short period in mid- to later-life led to a meaningful slowing of memory decline and reduction in dementia probability seven years later. Cash transfer programs could help to stem the tide of new dementia cases in LMIC settings in the coming decades.Trial Registration: NCT01233531.Funding: This work was supported by the National Institute on Aging of the National Institutes of Health (grant number R01AG069128). The Agincourt Health and socio-Demographic Surveillance System is supported by the National Department of Science and Innovation, the Medical Research Council and University of the Witwatersrand, South Africa, and previously the Wellcome Trust, UK (grants 058893/Z/99/A; 069683/Z/02/Z; 085477/Z/08/Z; 085477/B/08/Z). The HPTN 068 was supported by the National Institutes of Health (grant numbers R01MH087118 and R24 HD050924) and overall support to the HPTN through National Institute of Allergy and Infectious Diseases (NIAID), the National Institute of Mental Health (NIMH), and the National Institute on Drug Abuse (NIDA) of the National Institutes of Health (NIH; award numbers UM1AI068619 [HPTN Leadership and Operations Center], UM1AI068617 [HPTN Statistical and Data Management Center], and UM1AI068613 [HPTN Laboratory Center]. HAALSI is supported bv the National Institute on Aging (P01AG041710, R01AG054066). Declaration of Interest: The authors declare no conflicts of interest.Ethical Approval: The protocols for HPTN 068 and HAALSI were reviewed and approved by Institutional Review Boards at the and University of the Witwatersrand and the Mpumalanga Provincial Research and Ethics Committee. The protocols were additionally reviewed by the University of North Carolina-Chapel Hill (HPTN 068) and the Harvard T.H. Chan School of Public Health (HAALSI). The protocol for this secondary analysis was reviewed and approved by the Institutional Review Board at Indiana University (deemed ‘not human subjects research’ with its use of fully deidentified datasets: #2002584956), and the University of the Witwatersrand (#M20056).