Weight change, body weight and mortality: the impact of smoking and ill health.

OBJECTIVES This paper examines the influence of cigarette smoking and ill health on the relationship between weight change, body weight and subsequent mortality to determine whether weight loss and leanness in middle to older age is deleterious to health. METHODS Men aged 40-59 years at screening drawn from one general practice in each of 24 British towns, who completed a questionnaire 5 years after screening (Q5) and provided full information on changes in weight and smoking status (n = 7065) were then followed up for an average of 13.8 years. RESULTS In all men a shallow U-shaped relationship was seen between body mass index (BMI) at Q5 and all-cause mortality rates. Weight loss and substantial weight gain (> or =10%) were associated with increased mortality rates compared to the stable weight group. The increased risk associated with weight loss was seen in long- term non-smokers (n = 4101) and recent ex-smokers (n = 722) but not in current smokers (n = 2242) after adjustment for a wide range of potential confounders. However, the increased risk was markedly attenuated after exclusion of those with ill health (relative risk [RR] = 1.16, 95% CI : 0.84-1.59 and RR = 0.79, 95% CI : 0.29-2.20 for long-term non-smokers and recent ex-smokers, respectively). Moderate weight gain (4-10%) was associated with lower risk of mortality than observed in those with stable weight but only in recent ex-smokers and in current smokers, not in long-term non-smokers. A positive association was seen between BMI at Q5 and all-cause mortality in non-smokers and this was strengthened by exclusion of men with weight loss. CONCLUSION The increased risk of mortality associated with weight loss or low body weight in middle-aged and older men appears to be a direct consequence of ill health leading to weight loss and leanness. In healthy non-smoking men weight loss and leanness are not associated with increased mortality and moderate weight gain (4-10%) was neither deleterious nor beneficial.