Body mass index and mortality: the influence of physical activity and smoking

• Published in: Medicine and science in sports and exercise Vol. 34; no. 7; p. 1065
• Main Authors: Meyer, Haakon E, Søgaard, Anne Johanne, Tverdal, Aage, Selmer, Randi M
• Format: Journal Article
• Language: English
• Published: United States 01.07.2002
• Subjects: Adult; Body Mass Index; Comorbidity; Confounding Factors (Epidemiology); Exercise - physiology; Humans; Male; Middle Aged; Norway - epidemiology; Obesity - epidemiology; Obesity - mortality; Physical Fitness; Prospective Studies; Risk Assessment; Smoking - epidemiology; Smoking - mortality; Norway
• ISSN: 0195-9131; 1530-0315
• DOI: 10.1097/00005768-200207000-00002

To study the association between body mass index (BMI) and mortality, and to evaluate the effect of physical activity during leisure time and smoking on this association in a general male population. During 1974-1978, all men aged 35-49 yr living in three Norwegian counties were invited to a cardiovascular screening, and 87.1% attended and had their weight and height measured. Men with recognized cardiovascular diseases, diabetes mellitus, or cancer at screening were excluded. The cohort (N = 22,304) was followed for an average of 16.3 yr with respect to total and cause-specific mortality. During follow-up, 1909 men died. We found a J-shaped association between BMI and total mortality, and the form of association was similar for death from cardiovascular diseases. Although not statistically significant, a J-shaped association was also suggested in never-smokers. Irrespective of BMI level, ex- and never-smokers had lower mortality than current smokers. Obese smoking men had a relative risk of dying of 2.01 (95% CI: 1.29-3.11) compared with obese never-smokers, and a relative risk of 4.55 (95% CI: 3.34-6.20) compared with normal weight never-smokers (BMI 22-24.9 kg x m(-2)). Within each category of physical activity during leisure time, obese men had a similar increased relative risk of death compared with normal-weight individuals. However, the U- to J-shaped association between BMI and mortality seemed to disappear by increasing level of physical activity, but this finding was not significant. This study suggests a J-shaped association between BMI and total mortality, also when stratified on smoking habits and physical activity. The suggested linear trend in the most physical active men needs to be reassessed.