Longer secondary education protects against HIV infection, Botswana study shows

Every additional year of schooling among young people in Botswana was associated with an 8% reduction in the risk of HIV infection in the years between 2004 and 2008, according to a study published last week in Lancet Global Health. The study provides further strong evidence that improving retention in education protects against HIV infection, especially for girls, say the authors.

Although some studies, conducted in South Africa, Zambia and Uganda have shown that a greater duration of education is associated with a lower likelihood of being HIV-positive, evidence from randomised studies of interventions which keep young people in school is mixed regarding their effects. This may be because the mechanisms by which education is linked to a reduced risk of acquiring HIV are not direct. For example, being at school all day might not be protective, and sex education acquired during school time might not be protective, but on the other hand, having a higher level of education may enable young people – especially girls – to gain jobs and livelihoods that will place them at lower risk of HIV infection, and make them less vulnerable to economic pressures for transactional sex.

The clearest evidence of a positive effect was found in a study of cash transfers for school-age adolescent girls in Malawi. Even here, the study found no difference between cash transfers that were unconditional or those that were conditional on attending school – leading to speculation that the effect could well be economic.

Glossary

cost-effective

Cost-effectiveness analyses compare the financial cost of providing health interventions with their health benefit in order to assess whether interventions provide value for money. As well as the cost of providing medical care now, analyses may take into account savings on future health spending (because a person’s health has improved) and the economic contribution a healthy person could make to society.

sample

Studies aim to give information that will be applicable to a large group of people (e.g. adults with diagnosed HIV in the UK). Because it is impractical to conduct a study with such a large group, only a sub-group (a sample) takes part in a study. This isn’t a problem as long as the characteristics of the sample are similar to those of the wider group (e.g. in terms of age, gender, CD4 count and years since diagnosis).

p-value

The result of a statistical test which tells us whether the results of a study are likely to be due to chance and would not be confirmed if the study was repeated. All p-values are between 0 and 1; the most reliable studies have p-values very close to 0. A p-value of 0.001 means that there is a 1 in 1000 probability that the results are due to chance and do not reflect a real difference. A p-value of 0.05 means there is a 1 in 20 probability that the results are due to chance. When a p-value is 0.05 or below, the result is considered to be ‘statistically significant’. Confidence intervals give similar information to p-values but are easier to interpret. 

circumcision

The surgical removal of the foreskin of the penis (the retractable fold of tissue that covers the head of the penis) to reduce the risk of HIV infection in men.

retention in care

A patient’s regular and ongoing engagement with medical care at a health care facility. 

The lack of clarity on the effect of duration of schooling led researchers at Harvard School of Public Health, the Botswana-Harvard AIDS Institute and Boston University’s Center for Global Development to look at the effect of a change in educational policy that encouraged young people to stay in school on HIV prevalence in Botswana between national surveys in 2004 and 2008.

In 1996 Botswana shifted the incorporation of year 10 into junior secondary schools. In order to qualify for most vocational programmes young people must complete junior secondary school, so the effect of the change was to encourage an average of one extra year of education for young people after 1996.

Botswana also had good data on HIV prevalence among young people affected by the change in policy, gathered through national AIDS Impact Surveys conducted in 2004 and 2008. Using this data Jan-Walter De Neve and colleagues analysed the effects of the policy change on educational attainment, on years of schooling and on HIV status of young people affected by the policy change compared to those not affected, after controlling for age.

AIDS Impact Survey data was available for 7018 respondents (3965 women and 3053 men) with HIV antibody information who were born after 1975 and aged over 18 years at the time of sampling. In this study sample the reform increased the average number of years of schooling by 0.79 years (P<0.0001). Among this sample the baseline HIV prevalence was 25.5%, but the cumulative risk of HIV infection was reduced by 8.1% for each additional year of schooling caused by the policy change. (p=0.008) Each additional year of schooling after the completion of nine years of schooling was associated with a reduction in risk, but schooling prior to this point was not protective.

The effect was significant for both women and men, although the effect was stronger in women (11.6% reduction in risk for each year of additional schooling, p=0.046).

The cost per HIV infection averted was $27,753, and the investigators calculated that assuming anyone infected with HIV would eventually start antiretroviral therapy with a lifetime cost of $12,400, the incremental cost-effectiveness ratio of a year of secondary education would be $4387, making it highly cost effective by World Health Organization standards. The authors note that although circumcision and treatment as prevention would be cheaper buys from an HIV prevention perspective, their analysis does not factor in the wide economic benefits of additional education.

The authors speculate that the change in schooling duration resulting from the Botswana policy change may have affected HIV risk because years 10 to 12 are “a period where sexual behaviour patterns and labour market opportunities are formed.” They caution that the effects might not be similar in settings with a lower HIV prevalence, and that the results are a snapshot of the effects of the reforms during the mid-2000s, the decade after the policy change.

Professor Jacob Bor of Boston University’s Center for Global Development, a study investigator, said: "This study is among the first to provide 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."

References

De Neve JW et al. Length of secondary schooling and risk of HIV infection in Botswana: evidence from a natural experiment. Lancet Global Health, advance online publication, 29 June 2015.