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In many countries obesity has increased dramatically during the last decades, while there has been a parallel decrease in smoking. The objective of the present study was to estimate the net effect on premature mortality of these trends. A simulation model was developed to estimate the expected number of deaths between ages 19-56 years for cohorts of young men (n = 50,000), depending on inputs of obesity and smoking prevalence. The model was populated with nationwide data of Swedish men performing mandatory military conscription tests between 1969 and 2005. Risk equations for all cause mortality with smoking and obesity status as predictors were developed based on the 1969-1970 conscription cohort (n = 45,920; 2,897 deaths, median follow-up 38 years). It was found that between 1969 and 2005, the prevalence of smoking decreased from 58.6 to 23.2%, while overweight increased from 5.7 to 15.6% and obesity from 0.8 to 5.5%. As a result of these trends, a 14% (CI₉₅(%) 6, 21%) reduction of premature deaths between ages 19 and 56 years was forecasted for men aged 19 year in 2004-2005 compared to men aged 19 years in 1969-1970 (2,679 vs. 3,116 deaths). However, one-third of the survival benefit from reduced smoking during the period was offset due to the parallel increase in obesity. This study shows that despite large increases in overweight and obesity, a continued decline in premature deaths among Swedish males is expected due to reduced smoking during the last four decades.

Background: Smoking and obesity are two of the most important risk factors for chronic disease today. Their combined effect on the risk of disability pension is not known., Methods: A nationwide cohort of 45 920 Swedish men (18.7 + or - 0.5 years) were followed for 38 years. The body mass index (BMI), based on measured height and weight, was used to define underweight (<18.5), normal weight (18.5-24.9), overweight (25.0-29.9) and obesity (> or = 30.0). The hazard ratios (HRs) associated with BMI and smoking status at baseline for receiving disability pension were adjusted for socio-economic index (SEI), muscular strength, geographic region and place of residence., Results: During 1.6 million person-years, 4631 disability pensions and 2897 deaths occurred. After adjustment, overweight (HR 1.34, 95% CI 1.19-1.51) and obesity (HR 1.55, 1.18-2.05) were associated with an increased risk of disability pension, independent of smoking, whereas underweight (18.5; HR 1.07, 0.97-1.17) was not compared with normal weight. Similarly, smoking 1-10 (HR 1.37, 1.27-1.49) or >10 cigarettes per day (HR 2.01, 1.86-2.17) showed independent risk increases versus non-smoking. Although obese individuals smoking >10 daily cigarettes were at greatly increased risk (HR 2.98, 1.98-4.47), no evidence of interaction between the two risk factors could be detected., Conclusions: Both increased adiposity and smoking are strong and independent predictors of disability pension, but they do not act synergistically.