Effects of Low Body Mass Index and Smoking on All-cause Mortality among Middle-aged and Elderly Japanese.

Abstract

To investigate effects of low body mass index (BMI) and smoking on all-cause mortality among middle-aged and elderly Japanese, we conducted a community-based prospective study. A mail survey was conducted in 1987-1990 in four towns, western Japan. A cohort of 7,301 Japanese men and 8,825 Japanese women was followed up from the date of the mail survey to 1995 in three of the towns and 1998 in the fourth town. We investigated the effect of BMI and smoking on all-cause mortality by using Cox's proportional hazards model. The relationship between BMI and all-cause mortality was a reverse J-shape with minimal mortality in 24 < or = BMI < 26 in men and a U-shape with minimal mortality in 22 < or = BMI < 24 in women, after adjusting for age and smoking. The lowest BMI category (BM < 20) had the highest all-cause mortality in men and also in women. Taking only never-smokers, the highest risk for all-cause mortality was observed in the lowest BMI category for men and for women. This does not seem to be explained by smoking and pre-existing diseases. More attention should be paid to persons with low BMI.

Body mass index and all-cause mortality in a large Chinese cohort

“…[22][23][24] Our findings support the results of previous studies that have shown smokers who have lower BMI values to be at higher risk of death than those who never smoked. 12,23 We found similar Ushaped associations between BMI and all-cause mortality among participants who never smoked, smokers who had fewer than 10 cumulative pack-years and smokers with 10 or more packyears.…”

Body Mass Index and Mortality: A 10-Year Prospective Study in China

“…As revealed in several studies, smoking was associated with lower body weight and an increased risk of mortality, and can therefore distort the relationship between BMI and risk of mortality25262728, and adjustment for smoking cannot fully address the issue. Sensitivity analysis by excluding smokers is a more powerful method to address this potential bias.…”

Body Mass Index and Mortality in Japan: The Miyagi Cohort Study

“…Although some results from previous studies have showed that obese subjects had much higher risks of death than those of normal weight subjects, 4,5,[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] other results have not showed the elevation of the risks. 4,10,18,19,21,[24][25][26][27][28][29] This discrepancy have been attributed to failure to properly take cigarette smoking into account and lack of exclusion of individuals with weight loss-related illness.…”

“…Although the adverse health effects of obesity are widely accepted, [1][2][3] the impact of obesity upon mortality is less well established and debates about the effects of leanness still continue. [4][5][6][7] Epidemiologic studies have reported six major patterns regarding the association between body mass index (BMI), weight (kg) divided by the square of height (m), and mortality linearly positive, [8][9][10][11][12][13][14] J-shaped, [11][12][13]15 U-shaped, 4,5,10,12,[16][17][18][19][20][21][22][23][24] inverse J-shaped, 10,19,21,[24][25][26][27][28] linearly inverse, 18,25,29 or no association. 4,27 This discrepancy have been attributed to methodological problems including failure to control for confounding by smoking and failure to exclusion of individuals with weight loss-related illness.…”