Association of BMI with mortality

31 Oct 2018

Body Mass Index (BMI), a measure of body fat, is linked to risk of death from every major cause except transport accidents, according to new research by the LSHTM Electronic Health Records Research Group.

The study is one of the largest of its kind to look at how BMI is associated with the risk of death both overall, and from a full spectrum of different causes – 3.6 million people and 367,512 deaths were included in the analysis. Overall, both low and high BMI were associated with an increased risk of death. BMI of between 21-25kg/m was associated with the lowest risk of dying from cancer and heart disease.

The research team used anonymised data from the UK Clinical Practice Research Datalink (CPRD) which includes data on BMI from general practitioners’ primary care records covering about 9% of the UK population. This is linked to data from the Office of National Statistics mortality database, which includes information on causes of death as recorded on death certificates. Risks of death from each major cause was calculated according to BMI, adjusting for other important factors such as age, sex, smoking status, alcohol use, and socioeconomic status.

Lead author Krishnan Bhaskaran said: “BMI is a key indicator of health. We know that BMI is linked to the risk of dying overall, but surprisingly little research has been conducted on the links to deaths from specific causes. We have filled this knowledge gap to help researchers, patients and doctors better understand how underweight and excess weight might be associated with diseases such as cancer, respiratory disease and liver disease.

“We found important associations between BMI and most causes of death examined, highlighting that body weight relative to height is linked to risk of a very wide range of conditions. Our work underlines that maintaining a BMI in the range 21-25kg/m2 is linked to the lowest risk of dying from most diseases.”

The authors acknowledge limitations of the study including that there was no information was available on the diet or physical activity levels of people included in the study so it was not possible to look at the interplay between BMI and these related factors. The full article was published in The Lancet Diabetes & Endocrinology.