Long term effects of smoking on physical fitness and lung function: a longitudinal study of 1393 middle aged Norwegian men for seven years

Abstract

Objective:to study association between smoking habits and long term decline in physical fitness and lung function in middle aged men who remained healthy. Design: Baseline and follow up measurements performed during 1972-5 and 1980-2 respectively. Setting:National University Hospital of Oslo, Norway. Subjects:1393 men aged 40-59 at baseline who were all healthy at baseline and at follow up. Main outcome measures:Forced expiratory volume in one second and physical fitness (defined as total work done during a symptom limited bicycle ergometer test divided by body weight. Results: Initial fitness was substantially lower among 347 persistent smokers than among 791 persistent non-smokers (1349 J/kg v 1618 J/kg), as was initial forced expiratory volume (3341 ml v 3638 ml). Mean (95% confidence interval) decline in fitness over 7.2 years was 217 (185 to 249) J/kg among smokers compared with 86 (59 to 113) J/kg among non-smokers (P<0.001). Corresponding declines in forced expiratory volume were 271 (226 to 316) ml in smokers and 116 (85 to 147) ml in non-smokers (P<0.001). Differences between smokers and non-smokers remained practically unchanged after adjustment for age and level of physical activity. Changes in fitness and forced expiratory volume among 199 men who had stopped smoking mimicked the findings for persistent non-smokers, and 56 men who started smoking presented findings close to those of persistent smokers Conclusion:Decline in physical fitness and lung function among healthy middle aged men was considerably greater among smokers than among nonsmokers and could not be explained by differences in age and physical activity.