Men who have a high body mass index (BMI) - the ratio of weight to height - in early adulthood appear to have a lower risk of suicide later in life, according to researchers in Sweden and the UK.

Dr. Finn Rasmussen, of the Karolinska Institute, Stockholm, and colleagues examined the association between BMI and suicide risk using linked data from the Swedish Military Service Conscription Register, the Population and Housing Censuses, and the Cause of Death Register.

The study included 1,299,177 Swedish men conscripted from 1968 to 1999. The subjects had their BMI measured at 18 to 19 years of age and were followed for up to 31 years. BMI is commonly used to determine if a person weighs too much or too little. The higher the BMI, the more likely a person is overweight or obese.

The researchers found that the suicide rate was 16.2 per 100,000 per year, with an average age at death of 30 years. The risk of suicide decreased by 15 percent for every 5-point increase in BMI. A similar association was observed when the 67,417 individuals with mental disorders at the start of the study were excluded from the analysis.

The team examined if the BMI-suicide association diminished over time. They found similar associations in analyses performed for suicides occurring less than 5 years, 5 to 10 years, and more than 10 years after BMI measurement.

This suggests that “weight loss as a consequence of mental illness does not explain the BMI-suicide association,” Dr. Rasmussen’s team notes in their report, published in the American Journal of Epidemiology. The findings also suggest that BMI influences the development of mental disorders that lead to suicide.

However, because higher BMI is also associated with increased risk of cardiovascular disease, diabetes and cancer, the investigators do not recommend interventions to increase BMI to prevent suicide.

SOURCE: American Journal of Epidemiology, January 2006.