In Richard Walker and colleagues report the results of
In , Richard Walker and colleagues report the results of a case-control study of risk factors for stroke in Tanzania. Their study makes several important contributions. First, they provide the first information about importance of risk factors for stroke in urban and rural Tanzania, and confirm the feasibility of undertaking challenging stroke research in a low-income setting, for which the investigators should be congratulated. A key challenge in stroke research is identification of stroke subtype, because even the major distinction between ischaemic and haemorrhagic stroke requires neuroimaging, which is not completed in many patients in low-income settings because of poor availability and access and high costs. Neuroimaging is also required for exclusion of some non-stroke causes. In Walker and colleagues\' study, less than half of patients underwent CT scans of the brain.
Second, the investigators report the importance of known modifiable risk factors for stroke, of which hypertension, smoking, and hypercholesterolaemia were the most important. The prevalence of Special Health Care Needs in cases and controls was very high, making it a key modifiable risk factor for stroke in Tanzania. Country-specific and region-specific information about risk factors for stroke is an essential step for raising of local awareness to inform health policy, even when information about some risk factors, such as hypertension, is largely confirmatory. The risk associated with dyslipidaemia (odds ratio 4·54, 95% CI 2·49–8·28) was higher than that reported in previous epidemiological studies, which might suggest that this disorder could be a greater risk factor in Africa than in other regions; however, this notion requires confirmation in larger studies. The study did not obtain data for diet, physical activity, or obesity, which are also likely to be important.
Third, Walker and colleagues provide information about emerging risk factors for stroke, which might have importance for specific approaches to prevent stroke in Tanzania. In this regard, the importance of HIV infection is a notable finding, and associated with a increase of five times in risk of stroke, which is larger than that reported in previous studies. However, HIV status was missing in 44% of the cohort and the methods of case recruitment might have introduced a selection bias for this risk factor. Furthermore, because only 40% of cases underwent neuroimaging, non-stroke causes might have been included among cases. Nevertheless, these findings are provocative, and should prompt future studies to examine brain important issue in larger studies.
In , Michael Pickles and colleagues show how Avahan, a large-scale prevention programme in India targeting female sex workers and men who have sex with men, is estimated to have averted about 202 000 HIV infections in its first 4 years and 606 000 infections over 10 years. These estimates are higher than that from a previous assessment by Ng and colleagues, which suggested that Avahan had prevented 100 200 infections in the first 5 years of implementation. These estimates can be challenged because of the levels of uncertainty related to the methods and assumptions used within the modelling. However, the central message of this study is that this large-scale, targeted HIV prevention programme has been effective. Hundreds of thousands of HIV infections were averted through a combination prevention package addressing risk and vulnerability, customised to the needs of the populations. Much has been documented about Avahan and its achievements, but Pickles and colleagues\' results are important for several reasons. First, the study reinforces the notion that HIV prevention for marginalised and stigmatised populations such as sex workers is not only feasible, but also works. Since the beginning of the epidemic in the late 1980s, high rates of HIV have been reported in sex workers and evidence for effective condom promotion and prevention strategies for HIV or sexually transmitted disease emerged. Data for the effect of large-scale prevention programmes for sex workers are still scarce, mainly because scale and coverage of programmes for sex workers is low worldwide. And where national programmes do exist, insufficient investment is made for monitoring and assessment to allow for estimations of effect. Avahan, one of the largest prevention programmes in the world, had the vision and the capacity to build in an assessment system from the start, based mainly on extensive monitoring of the implementation and uptake of the programme components. In addition to providing the wealth of assessment data produced by Avahan, the report by Pickles and colleagues is an invaluable contribution to the international HIV prevention knowledge base.