‘Body mass index can predict death’
Teenagers who have a high body mass index – a calculation of a person’s weight in kilograms divided by the square of their height in meters – are at greater risk to die of cardiovascular disease when they are middle aged, reports the New England Journal of Medicine.
A nationwide study carried out by Prof. Jeremy Kark and Dr. Hagai Levine from the Hebrew University-Hadassah Braun School of Public Health and Community Medicine, together with Dr. Gilad Twig of Sheba Medical Center, followed up the medical records of 2.3 million Israelis who were adolescents in 1967 and became middle aged by 2010. The researchers found an association between elevated BMI in late adolescence and subsequent cardiovascular mortality in midlife.
Around a third of teenagers in some developed countries, including Israel, are overweight or abuse. Some studies suggest that an elevated body-mass index is associated with an increased risk of death from cardiovascular causes. However, a determination of the BMI that is associated with increased risk of fatality has remained uncertain. The researchers assessed the association between BMI in late adolescence and death from coronary heart disease, stroke and sudden death in adulthood by mid-2011.
The results showed an increase in the risk of cardiovascular death in the group that was considered within the “accepted normal” range of BMI, in the 50th to 74th percentiles, and of death from coronary heart disease at BMI values above 20.
As BMI scores increased into the 75th to 84th percentiles, adolescent obesity was associated with elevated risk of death from coronary heart disease, stroke, sudden death from unknown causes, and death from total cardiovascular causes, as well as death from non-cardiovascular causes and death from all causes. Participants also had an increased risk of sudden death.
The rates of death per person-year were lowest in the group that had BMI values during adolescence in the 25th to 49th percentiles, although higher rates were observed among those below the 5th percentile.
The researchers considered two explanations why adolescent BMI influenced cardiovascular outcomes in adulthood. First, obesity may be harmful during adolescence, since it has been associated with unfavorable metabolic abnormalities. The timing of exposure to obesity during a person’s lifetime may play an important role, they suggested.
Secondly, BMI tends to “track” along the life course so that overweight adolescents tend to become overweight or obese adults, and overweight or obesity in adulthood affects the risk of cardiovascular disease.