The study, to be presented Sunday, July 18, at the International AIDS Conference in Vienna, Austria, found that people who were offered up to $60 each over 12 months to stay free of STIs had a 25 percent lower prevalence of those infections after a year compared to those who were not eligible for the money.
“For many of our study participants, $60 represented about one-fourth of their reported annual income, so it was a significant incentive,” said study author Will Dow, UC Berkeley professor of health economics. “The question we tested is whether the cash reward was enough of an incentive to reduce risky behavior and better take advantage of available health services. Although we cannot directly measure risky behavior, the fact that disease prevalence decreased suggests that the incentives worked.”
Dow teamed up with Damien de Walque, a senior economist at the World Bank, and Rose Nathan, a senior research scientist at the Ifakara Health Institute, to test the conditional cash transfer program, an increasingly popular concept in the public health field that essentially rewards desirable behavior with money.
The year-long Rewarding STI Prevention and Control in Tanzania (RESPECT) study enrolled 2,399 adults from 10 villages in southwestern Tanzania. Rates of sexually transmitted infections in the region are comparable to the average rates for Africa.
Study participants were primarily 18 to 30 years old, a group considered at high risk for contracting STIs. They were randomly assigned to a no-payment control group, a low-payment group and a high-payment group. Over the year, participants in the low-payment group could get $10 every 4 months – up to $30 – if they tested negative for STIs, while those in the high-payment group could get $20 every 4 months, up to $60.
All participants were tested at the start of the study and every four months for the following year to detect a set of curable sexually transmitted infections, including chlamydia, gonorrhea and syphilis. Individual pre-test and post-test counseling was provided to study enrollees at each testing interval, and monthly group counseling sessions were also made available to all study participants to assist them in their efforts to reduce risky sexual behaviors.
HIV/AIDS was not linked to cash payments for both practical and ethical reasons, but the same risky sexual behaviors that increase the chances of the STIs tested also increase the risk of HIV, the researchers noted.
“Cash rewards have been proposed as a new HIV prevention tool to complement traditional approaches,” said Dow. “New prevention tools are desperately needed since five people become newly infected with HIV for every two getting enrolled in new AIDS treatment programs. This study is the first to show that cash rewards can reduce STI prevalence, and is a key step in determining whether it is worthwhile to launch a larger study to test whether cash rewards could in fact slow the HIV epidemic.”
At the end of the trial period, 9 percent of participants eligible for the $60 reward tested positive for the infections compared to 12 percent for the control group who were not eligible for payments. Any participant who tested positive for an STI during the study received free medical treatment and counseling.
“These are very encouraging results,” said the World Bank’s de Walque. “This was a proof-of-concept study that we now think should be replicated on a larger scale before concluding that this is an effective and feasible prevention approach.”
Notably, the amount of cash offered mattered. The group that was eligible for the lower reward value had the same infection rate as the control group that received no payments. While the impact of the cash incentives did not differ between males and females, the impact was larger among people with lower incomes.
The project was funded by the World Bank, its Spanish Trust Fund for Impact Evaluation and, through the nonprofit Population Reference Bureau, the William and Flora Hewlett Foundation. The cash payments ended in May, and the researchers will test participants again next year to see if the cash group’s infection rate will hold without cash incentives.