From Heartwire CME News Author: Shelley Wood CME Author: Charles Vega, MD
april 15, 2011 — A large, prospective study tracking young men from age 17 well into their 30s, 40s, and beyond has found that body-mass index (BMI) in their teens was a significant predictor of both coronary artery disease and diabetes in later life . Strikingly, say the authors, BMI became predictive of later disease even at levels that would be considered normal or even low-normal by current cutoffs.
Speaking with heartwire , Dr Iris Shai (Ben-Gurion University of the Negev, Beer-Sheva, Israel), who with Dr Amir Tirosh (Brigham and Women's Hospital, Boston, MA) was a lead author on the study, highlighted just how unique their series was. The cohort consisted of Israeli army personnel, who had their height and weight measured when they entered the army, and, if they remained in the armed forces, again every three to five years. The data have been collected as part of the Metabolic, Lifestyle, and Nutrition Assessment in Young Adults (MELANY) study. For their study, Tirosh, Shai, and colleagues followed 37 674 army career personnel (all men) until their first diagnosis of CAD (by angiography) or diabetes or until they retired from military service (until December 31, 2007).
In all, 1173 men developed diabetes and 327 men developed CAD within 650 000 person-years of follow-up (mean of 17.4 years). Baseline BMIs ranged from about 17 to 28, and elevated BMIs were a significant predictor of both CAD and diabetes. When baseline BMIs were organized by deciles, however, a surprising picture emerged: according to researchers, the risk of diabetes, after adjustment for other risk factors, became statistically significant in the eighth decile, which included BMI levels ranging from 22.4 to 23.4. For CAD, the risk became statistically significant at even lower BMIs, those in the third decile, ranging from 19.01 to 19.69.
To heartwire , Shai acknowledged that a BMI of 19 falls below what is considered a normal, healthy weight in adults, but she stressed that this was in 17-year-old boys, who were not yet fully grown.
The notion that BMI in childhood or young adulthood can lead to heart disease and diabetes later in life is not new, Shai acknowledged. "What is new here is we found that once we had the second measurement of BMI, around the age of 30, the most dominant predictor of diabetes was the BMI at age 30--in other words, close to the incidence of disease." In contrast, she said, "the incidence of CHD is predicted by both age 17 and 30. This suggests that history counts--even when you are 17 years old--and most of these were young and healthy recruits to the army, so most had a BMI lower than 25."
The finding that higher BMI at an older age, but not at a younger age, was the better predictor of near-term diabetes, whereas high BMI mattered at both younger and older ages in terms of coronary disease, points to a difference in how BMI relates to later diseases, Shai said. BMI seems to exert a more "acute effect" on diabetes risk in later life, whereas excess weight at younger ages seems to set in motion the development of coronary heart disease. "If you are now in your 30s, but you were heavier when you were 17, but you lose weight, that could dramatically reduce your risk of diabetes" but does not protect against developing coronary disease.
The study findings "highlight the critical importance of considering BMI history when assessing the risk of coronary heart disease vs the risk of diabetes in overweight or obese young adults," the authors write. They also underscore the need for age-specific diabetes-prevention programs as something distinct from coronary-disease-prevention tactics.
Finally, Shai told heartwire , the study may help redefine "normal" BMIs in male adolescents. While she stopped short of saying their study warranted shifting the cutoffs for normal lower on the BMI continuum, she said that she believed their study would be useful for ongoing efforts to refine definitions of optimal BMI in young people.
1. Tirosh A, Shai I, Afek A, et al. Adolescent BMI trajectory and risk of diabetes versus coronary disease. N Engl J Med 2011; 364:1315-1325. Abstract
Physicians and the general public are paying increasing attention to the problem of obesity during adolescence. Not only has the rate of obesity among this age group increased significantly in the last 2 decades, but also obese teenagers are at increased risk for multiple negative health outcomes as adults. A study by Must and colleagues, which was published in the November 5, 1992, issue of The New England Journal of Medicine, described these outcomes. Overweight during adolescence predicted a higher risk for overall and CHD mortality among men, but not women. Men with a history of overweight during adolescence were also more likely to have incident colorectal cancer and gout, and overweight female teenagers were more likely to go on to have arthritis.
The current study uses a large patient cohort with a long duration of follow-up to further elucidate the risks of teenage overweight and obesity.