MedicalResearch.com Interview with:
Dr. Kaitlin Wade PhD
Research Associate and Early Career Researcher Representative
Integrative Epidemiology Unit (IEU)
Bristol Medical School (Population Health Sciences)
Faculty of Health Sciences
University of Bristol
MedicalResearch.com: What is the background for this study?
Response: Whilst severe obesity increases the risk of death in the population, there are conflicting results in the literature with some papers suggesting a protective effect of being overweight. Many observational studies also report a J-shaped association between body mass index – a measure of weight accounting for a person’s height – and mortality, where individuals who are underweight also have an increased risk of mortality compared to those within the ‘normal’ range. Such controversial findings are not without limitation, as bias by age, ill-health and other lifestyle factors are likely. One method to overcome the limitations of observational studies – Mendelian randomization – uses genetic variation in a person’s DNA to help understand the causal relationships between risk factors and health outcomes to provide a more accurate estimate of relationships by removing confounding factors (such as smoking, income and physical activity) and reverse causation (where people lose weight due to ill-health), which can explain conflicting findings in previous studies.
Until now, no study has used such a genetic-based approach to explore the link between body mass index and mortality.
MedicalResearch.com: What are the main findings?
Response: In this study, using measurements and mortality data from 500,000 people in the UK Biobank (a study of middle to late aged volunteers), we showed that every 5kg/m2 increase in body mass index was associated with an increase of 16% in the chance of death and specifically 61% for those related to cardiovascular diseases.
We were also able to show that the apparent optimum body mass index for survival was lower with Mendelian randomization analyses (within the normal weight rather than overweight range found with observational studies) and the association remained flatter over a larger range of body mass index.
MedicalResearch.com: What should readers take away from your report?
Response: The findings confirm that being overweight increases a person’s risk of death from all causes including cardiovascular diseases and various cancers.
MedicalResearch.com: What recommendations do you have for future research as a result of this work?
Response: These findings highlight the need for a global effort to reduce the surging levels of obesity within society and suggest that, in most cases, any reduction in body mass index to a normal, healthy level is likely to be beneficial.
MedicalResearch.com: Is there anything else you would like to add?
Response: This research was supported by the Wellcome Trust and included researchers associated with the Medical Research Council Integrative Epidemiology Unit, the Cancer Research UK Integrative Cancer Epidemiology Programme, the University of Bristol Population Health Sciences Institute and the University of Bristol NIHR Biomedical Research Centre. Professor Naveed Sattar is a member of the UK Biobank International Scientific Advisory Board and Enhancements Committee. This had no bearing on the study. The other authors declared no conflicts of interest.
Kaitlin H Wade, David Carslake, Naveed Sattar, George Davey Smith, Nicholas J Timpson. Body mass index and mortality in UK Biobank: revised estimates using Mendelian randomization. Obesity, 2018 [link]
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