BMI linked strongly to heart disease (Reported in Mind Your Bosy of The Straits Times dated 31 December 2009)

Cardiovascular disease linked to obesity may be worse than thought while health problems associated with being underweight may have been overstated, according to a study published by the British Medical Journal (BMJ) last week.

The paper, written by doctors in Britain and Sweden, seeks to finetune a well-known tool - the body mass index (BMI) - which is used to measure obesity and ill-health.

BMI entails taking one's weight in kilograms and dividing it by the square of one's height, in metres. A BMI of 25-30 is generally considered overweight while a figure of above 30 indicates obesity.

Previous studies have already found a big link between BMI and higher risk of death from cardiovascular disease, diabetes and some cancers.

In contrast, a low BMI - in other words, someone who is very skinny - is associated with increased mortality from respiratory disease and lung cancer.

However, many experts have questioned the findings about low BMI, arguing that the figures could be skewed by something called reverse causality.

For instance, diseases such as lung cancer in themselves cause weight loss, they argued. Smoking and poor socioeconomic circumstances may also cause bias.

Seeking to find out more, specialists from Britain's University of Bristol and the Karolinska Institute in Sweden set out to get a wider view of the BMI benchmark.

They measured BMI and mortality among more than a million pairs of Swedes, comprising mother-and-son pairs and father-and-son pairs, over 50 years.

They found strong patterns of mortality and BMI.

The link was especially noticeable for cardiovascular disease - for which prevailing estimates may be 'substantially underestimated' - as well as for diabetes and kidney cancer.

However, there was no evidence of an association between low BMI and an increased risk of respiratory disease and lung cancer mortality.

The findings are important, because they imply that obesity programmes can yield major health benefits, said the study.

AFP