Body mass index and all-cause mortality in a nationwide US cohort

Abstract

Objective: To investigate whether the nature of the relationship between body mass index (BMI (kg/m 2 )) and all-cause mortality is direct, J-or U-shaped, and whether this relationship changes as people age. Design: Prospective nationwide cohort study of US radiologic technologists (USRT). Subjects: Sixty-four thousand seven hundred and thirty-three female and 19 011 male certified radiation technologists. Methods: We prospectively followed participants from the USRT study who completed a mail survey in 1983-1989 through 2000. During an average of 14.7 years of follow-up or 1.23 million person-years, 2278 women and 1495 men died. Using Cox's proportional-hazards regression analyses, we analyzed the relationship between BMI and all-cause mortality by gender and by age group (o55 years; X55 years). We also examined risk in never-smokers after the first 5 years of follow-up to limit bias owing to the confounding effects of smoking and illness-related weight loss on BMI and mortality. Results: Risks were generally J-shaped for both genders and age groups. When we excluded smokers and the first 5 year of follow-up, risks were substantially reduced in those with low BMIs. In never-smoking women under the age of 55 years (excluding the initial 5-year follow-up period), risk rose as BMI increased above 21.0 kg/m 2 , whereas in older women, risk increased beginning at a higher BMI (X25.0 kg/m 2 ). Among younger men who never smoked (excluding the initial 5-year follow-up period), risk began to rise above a BMI of 23.0 kg/m 2 , whereas in older men, risk did not begin to increase until exceeding a BMI of 30.0 kg/m 2 . Conclusions: In younger/middle-aged, but not older, women and men, mortality risks appear directly related to BMI. The more complicated relationship between BMI and mortality in older subjects suggests the importance of assessing whether other markers of body composition better explain mortality risk in older adults.

Fat distribution in men of different waist girth, fitness level and exercise habit

“…For example, we estimate that 45 participants would be required in each group to give a 90% probability at the 5% level of significance of detecting differences of 0.8±0.96 mmol l À1 in low-density lipoprotein cholesterol concentration. [43][44][45] Our findings are in keeping with prospective studies suggesting that 'optimal' BMI is around 23 in young, white runners 46 and young white men in the general population; 47 but, these findings cannot be generalized to women, older adults and other groups. Cross-sectional data cannot be used to infer causality, but several randomized, controlled trials have found that aerobic exercise is accompanied by preferential reductions in visceral adipose tissue.…”

Bariatric surgery and reduction in morbidity and mortality: experiences from the SOS study

“…[1][2][3][4][5][6][7] Weight loss is known to be associated with improvement of intermediate risk factors for disease, 8 suggesting that weight loss would also reduce mortality. Although four retrospective, bariatric cohort studies have indicated that this may be the case, 9-12 the prospective, controlled, interventional studies showing that weight loss is in fact reducing mortality have been lacking.…”

Effects of physical activity, body mass index, waist-to-hip ratio and waist circumference on total mortality risk in the Swedish National March Cohort

“…Epidemiological studies have shown an inconsistent relationship between body mass index (BMI) and mortality risk, with associations being J-or U-shaped [4][5][6][7][8][9][10][11][12], direct linear [13][14][15][16] or absent [17,18]. This could be due to the inadequate control for smoking status and pre-existing chronic diseases, both of which are associated with a low BMI and an increased risk of death [19].…”