Body fat and fat-free mass and all-cause mortality.

OBJECTIVE: To investigate whether the association between BMI and all-cause mortality could be disentangled into opposite effects of body fat and fat-free mass (FFM). RESEARCH METHODS AND PROCEDURES: All-cause mortality was studied in the Danish follow-up study "Diet, Cancer and Health" with 27,178 men and 29,875 women 50 to 64 years old recruited from 1993 to 1997. By the end of year 2001, the median follow-up was 5.8 years, and 1851 had died. Body composition was assessed by bioelectrical impedance. Cox regression models were used to estimate the relationships among body fat mass index (body fat mass divided by height squared), FFM index (FFM divided by height squared), and mortality. All analyses were adjusted for smoking habits. RESULTS: Men and women showed similar associations. J-shaped associations were found between body fat mass index and mortality adjusted for FFM and smoking. The mortality rate ratios in the upper part of body fat mass were 1.12 per kg/m2 (95% confidence interval: 1.07, 1.18) in men and 1.06 per kg/m2 (95% confidence interval: 1.02, 1.10) in women. Reversed J-shaped associations were found between FFM index and mortality with a tendency to level off for high values of FFM. DISCUSSION: Our findings suggest that BMI represents joint but opposite associations of body fat and FFM with mortality. Both high body fat and low FFM are independent predictors of all-cause mortality.

The validity of self-reported use of hormone replacement therapy among Danish nurses.

BACKGROUND: Recent findings from randomized clinical trials on the effects of hormone replacement therapy (HRT) among postmenopausal women contradict findings from observational studies indicating a protective effect on the development of cardiovascular disease. Most observational studies on HRT are based on self-reported data, although data on the validity of HRT in postmenopausal women are sparse. METHODS: We examined self-reported HRT use from questionnaires administered in 1993 (n = 2694) and again in 1999 (n = 2666) to a cohort of Danish nurses living in two Danish counties compared with prescription-reimbursement data from two administrative databases through the Danish National Health Service. RESULTS: The sensitivity and specificity of the self-reported, current HRT use in 1993 were 78.4%[95% confidence interval (95% CI) 75.4-81.4] and 98.4% (95% CI 97.8-98.9), respectively. In 1999, the estimates were 74.8% (95% CI 72.0-77.7) and 98.0% (95% CI 97.3-98.8), respectively. None of the factors examined--including age, alcohol intake, physical activity, smoking, presence of hypertension, and body mass index--was strongly associated with validity. We found a relatively high validity of self-reported data on HRT use. Furthermore, agreement between self-reported and registry-based data was not strongly associated with a range of demographic and lifestyle factors. CONCLUSION: These findings suggest that use of self-reported data is not an important contributor to the apparent discrepancy between observational studies and randomized trials on the cardiovascular effects of HRT use.