Man lying in a hospital bed at Hadassah University Medical Center in Jerusalem’s Ein Kerem [illustrative]..
(photo credit: MARC ISRAEL SELLEM/THE JERUSALEM POST)
Teenagers who have a high or even somewhat elevated 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.
This was discovered in a study 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 and other colleagues. It was just published in the prestigious New England Journal of Medicine.
The nationwide study followed up the medical records of 2.3 million Israelis who were adolescents in 1967 and became middle aged by 2010. The researchers found a clear 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 -- categorizing the individual as underweight, normal weight, overweight or obese -- 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.
During 42,297,007 person-years of follow-up, 2,918 of 32,127 deaths (9.1%) were from cardiovascular causes, including 1,497 from coronary heart disease, 528 from stroke and 893 from sudden death.
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. The researchers concluded that even BMI considered “normal” during adolescence was associated with a graded increase in cardiovascular and all-cause mortality during the 40 years of follow-up.
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 generally 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 possible pathways to explain why adolescent BMI influenced cardiovascular outcomes in adulthood. First, obesity may be harmful during adolescence, since it has been associated with unfavorable metabolic abnormalities through risk factors such as unfavorable plasma lipid or lipoprotein levels, increased blood pressure, impaired glucose metabolism, insulin resistance and formation of coronary and aortic atherosclerotic plaques. 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.
“Our findings appear to provide a link between the trends in adolescent overweight during the past decades and coronary mortality in midlife,” said Kark. “The continuing increase in adolescent BMI and the rising prevalence of overweight and obesity among adolescents may account for a substantial and growing future burden of cardiovascular disease, particularly coronary heart disease.”