Remembering the “prevention basics”
Authors: Zoë Mullan
Journal: The Lancet Global Health (2013)

Stroke is second only to ischaemic heart disease as the leading cause of death worldwide; one in six people will have a stroke in their lifetime. World Stroke Day, on October 29, reminds us of these striking facts and the need for individuals to know the risk factors. Although the main risk factors for stroke worldwide—hypertension, smoking, poor diet, and low levels of physical activity—are well established, potential regional variations may well be of importance to national prevention and treatment strategies. These variations could arise from differences in the subtype of stroke (ischaemic or haemorrhagic) prevalent in a particular region, or to the presence of specific epidemiological conditions. These factors are of course likely to be inter-related. In this month's issue, two papers address uncertainties in the burden and risk factors for stroke globally, regionally, and locally. Rita Krishnamurthi and colleagues use Global Burden of Disease 2010 methods to estimate trends in the incidence of and mortality and morbidity due to ischaemic and haemorrhagic stroke globally between 1990 and 2010. They show that, although the incidence of both ischaemic and haemorrhagic strokes decreased in high-income countries over these two decades, the incidence of haemorrhagic stroke increased by 22% in low-income and middle-income countries. Although haemorrhagic strokes comprised only a third of all stroke events worldwide, they accounted for more than half of all stroke deaths and 62% of disability-adjusted life-years (DALYs) lost. In 2010, the overwhelming majority (>80%) of haemorrhagic stroke burden, in terms of absolute numbers, deaths, and DALYs lost, was borne by low-income and middle-income countries, particularly central and east Asia and east and southern sub-Saharan Africa. The authors conclude that, to identify those at greatest risk in these regions, “high-quality community-based epidemiological studies in low-income and middle-income countries…are needed…because heterogeneity is likely to exist”. Richard Walker and colleagues' study is one such piece of research. These authors examined stroke risk factors in a prospective case–control study in two regions (urban and rural) of Tanzania. The study confirmed the link with hypertension and smoking, but also produced the striking finding that HIV infection was the biggest independent risk factor (other than previous transient ischaemic attack or stroke). The association could not have been due to any adverse effects of antiretroviral drugs because none of the patients was taking or had ever taken any. This provocative finding, if confirmed, presents a key target for further mechanistic research and for specific interventions in HIV-infected individuals. Targeted prevention of HIV itself is the focus of the third Article in this issue. Michael Pickles and colleagues' report is a preplanned assessment of the India AIDS Initiative, Avahan, which was rolled out in 2004 and aimed to reduce HIV transmission in some of India's highest-risk groups—female sex workers, men who have multiple male sexual partners, and intravenous drug users. The assessment goes beyond previous attempts to assess the programme's population-level effect by estimating the effect of the programme on consistent condom use in the targeted high-risk groups, then using mathematical modelling to estimate the effect of increased condom use on HIV prevalence in south India as a whole. The researchers estimate that around 600 000 HIV infections could have been averted over 10 years of Avahan's implementation. The evidence for the effectiveness of “prevention basics for and by key populations” is overwhelming, states Marie Laga in her linked Comment. She reminds us that exciting new strategies such as treatment-for-prevention must be accompanied by continued promotion of behavioural strategies that are known to work. The notion of “prevention basics” is as relevant to stroke as it is to HIV, particularly in low-income and middle-income countries where prompt treatment might not be as accessible as in high-income regions. Population-wide strategies to reduce salt consumption, control tobacco, and encourage healthy diets and active lifestyles should go hand-in-hand with national-level research similar to that by Walker and colleagues to identify additional targets specific to that population. Effect of HIV prevention in key populations: evidence accumulates, time to implementIn The Lancet Global Health, Michael Pickles and colleagues1 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,2 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. Full-Text PDF Open AccessGlobal and regional burden of first-ever ischaemic and haemorrhagic stroke during 1990–2010: findings from the Global Burden of Disease Study 2010Although age-standardised mortality rates for ischaemic and haemorrhagic stroke have decreased in the past two decades, the absolute number of people who have these stroke types annually, and the number with related deaths and DALYs lost, is increasing, with most of the burden in low-income and middle-income countries. Further study is needed in these countries to identify which subgroups of the population are at greatest risk and who could be targeted for preventive efforts. Full-Text PDF Open AccessStroke risk factors in an incident population in urban and rural Tanzania: a prospective, community-based, case-control studyWe have identified many of the risk factors for stroke already reported for other world regions. HIV status was an independent risk factor for stroke within an antiretroviral-naive population. Clinicians should be aware of the increased risk of stroke in people with HIV, even in the absence of antiretroviral treatment. Full-Text PDF Open AccessAssessment of the population-level effectiveness of the Avahan HIV-prevention programme in South India: a preplanned, causal-pathway-based modelling analysisThis is the first assessment of Avahan to account for the causal pathway of the intervention, that of changing risk behaviours in female sex workers and high-risk men who have sex with men to avert HIV infections in these groups and the general population. The findings suggest that substantial preventive effects can be achieved by targeted behavioural HIV prevention initiatives. Full-Text PDF Open Access