Washington, June 29 (IANS): Longer secondary schooling reduces the risk of contracting HIV, particularly for girls, shows a study.

Students with longer secondary education had an eight percent lower risk of HIV infection, about a decade later, from about 25 percent to about 17 percent infected, found the research from Botswana.

"It is difficult to isolate the effect of education on HIV risk from the complex web of co-factors such as personal motivation, psychological traits, socio-economic status and family background. In the absence of large-scale trial data, natural experiments can provide robust evidence to guide policy," said senior author Jacob Bor, assistant professor at Boston University School of Public Health.

The study used a recent school policy reform as a 'natural experiment' to determine the impact of increased years of secondary schooling on risk of HIV infection.

The authors examined the causal effect of an additional year of schooling on HIV status in 7018 men and women at least 18 years old at the time of the surveys.

Individuals with an extra year of secondary schooling were eight percentage points less likely to test positive for HIV about a decade later.

The effects were particularly strong among women, with each additional year of secondary schooling reducing infection risk by 12 percentage points.

"This study provides causal evidence that secondary education is an important causal determinant of HIV infection. Our results suggest that schooling should be considered alongside other proven interventions as part of a multi-pronged 'combination' HIV prevention strategy."

"Expanding the opportunities of young people through secondary schooling will not only have economic benefits but will also yield health benefits and should be a key priority for countries with generalised HIV epidemics."

The study appeared in The Lancet Global Health journal.