BMI and mortality: the limits of epidemiological evidence

734 www.thelancet.com Vol 388 August 20, 2016 Concurrent with the global increase in obesity, numerous studies and reviews have been published concerning associations of overweight and obesity with mortality. Their fi ndings have prompted considerable public health debate. There is ongoing discussion as to whether cutoff points for body-mass index (BMI) categories should diff er across regions or racial or ethnic groups. Additionally, studies diff er in their assessment of the relation between BMI and mortality. In particular, BMI in the overweight category (BMI 25–<30 kg/m2) is not consistently associated BMI and mortality: the limits of epidemiological evidence well as research on primary prevention. Much of the global disease burden arises from smoking (about 6·2 million deaths and 144 million disability-adjusted life-years [DALYs]), excessive salt intake (3·7 million deaths and 74·3 million DALYs), sugar (0·1 million deaths and 6·2 million DALYs), and alcohol (2·8 million deaths and 99·3 million DALYs). Increasing public awareness of the harms of these risk factors could contribute to improved individual and community-driven self-management of lifestyle behaviours. Reduction of exposure to these risk factors at a population level (for example, reducing salt and sugar content in processed foods at the manufacturing stage) has been shown to be benefi cial for cardiovascular disease and overall health. Compelling evidence shows that taxation on these hazardous behavioural factors could represent a valuable strategy to improve health. Revenue from these taxations could and should be used to fund primary preventive programmes and research on stroke and other major non-communicable diseases. A 2012 resolution from the UN has mandated for all governments to achieve a 25% reduction in the burden from stroke and other non-communicable diseases by 2025. Cost-savings from the reduction of the burden of stroke and other non-communicable diseases could then be re-invested in health and other social programmes to fund primary prevention research and develop and implement sustainable evidence-based primary prevention strategies in their communities. Supported by non-government organisations and the health sector, as well as communities, industries, and individuals at risk for stroke or non-communicable diseases, these preventive programmes could slow down, stop, and eventually revert the stroke or noncommunicable disease epidemics. We have heard the calls for actions about primary prevention. Now is the time for governments, health organisations, and individuals to proactively reduce the global burden of stroke. Governments of all countries should develop and implement an emergency action plan for the primary prevention of stroke.