Obesity is a modifiable risk factor for acute myocardial infarction (MI), but lean body mass (LBM) may also be an important factor. Low LBM may increase the risk of MI and LBM may modify the effect of obesity on MI. Thus, the inability of the classical anthropometric measures to evaluate LBM may lead to misclassification of MI risk in both lean and obese persons. We investigated the associations between incident MI and bioelectrical impedance analyses (BIA) derived measures of body composition in combination with body mass index (BMI) and anthropometric measures of body fat distribution.
From 1993 to 1997, 27?148 men and 29?863 women, aged 50 to 64 year, were recruited into the Danish prospective study Diet, Cancer and Health. During 11.9 years of follow-up we identified 2028 cases of incident MI (1487 men and 541 women). BMI, waist circumference (WC), hip circumference and BIA of body composition including body fat mass (BFM), body fat percentage and LBM were measured at baseline. We used Cox proportional hazard models with age as time axis and performed extensive control for confounding. Weight, BMI, classical estimates of abdominal obesity and BIA estimates of obesity showed significant positive associations with incident MI. However, BFM adjusted for WC showed no association. Low LBM was associated with a higher risk of incident MI in both genders, and high LBM was associated with a higher risk in men.
Obesity was positively associated with MI. Estimates of obesity achieved by BIA seemed not to add additional information to classical anthropometric measures regarding MI risk. Both high and low LBM may be positively associated with MI.
Although the expectation is that weight gain increases mortality and weight loss among those overweight reduces mortality, results on weight gain and mortality in young adults are conflicting, and weight loss is less explored. We investigated the association between long-term weight change and all-cause mortality in a broad range of body mass index (BMI) in young men.
Among 362200 Danish draftees, examined between 1943 and 1977, all obese (BMI ?31.0?kg?m(-2); n=1930), and a random 1% sample of the others (n=3601) were identified at a mean age of 20 years (range: 18-25 years). All the obese and half the controls were re-examined between 4 and 40 years later (mean age 35 years). Weight changes were defined as: weight loss 0.1?kg?m(-2) per year. Hazard ratios (HR) and 95% confidence intervals (CI) were estimated using Cox regression.
Among the 908 obese and 1073 controls followed for 30 years after re-examination 220 and 232 died. HR of the weight stable obese was 2.32 (CI: 1.56-3.44) compared with the weight stable controls. In the obese cohort there was no association between weight loss, adjusted for initial BMI, and mortality (HR: 0.99; CI: 0.68-1.45) compared with weight stable obese. Too few controls lost weight to allow assessment of weight loss. Weight gain was associated with increased mortality in the obese (HR: 1.50; CI: 1.07-2.10) and controls (HR: 1.54; CI: 1.14-2.09) compared with weight stable obese and controls, respectively. Neither the time between the two examinations, life-style factors nor exclusion of diseased individuals influenced the results.
Although there were increased mortality of the weight-stable obese compared with controls, there was no association between weight loss and mortality in the obese. Weight gain increased mortality regardless of the initial weight.