Elsevier

The Lancet

Volume 365, Issue 9471, 7–13 May 2005, Pages 1629-1635
The Lancet

Articles
Smoking cessation, lung function, and weight gain: a follow-up study

https://doi.org/10.1016/S0140-6736(05)66511-7Get rights and content

Summary

Background

Only one population-based study in one country has reported effects of smoking cessation and weight change on lung function, and none has reported the net effect. We estimated the net benefit of smoking cessation, and the independent effects of smoking and weight change on change in ventilatory lung function in the international European Community Respiratory Health Survey.

Methods

6654 participants in 27 centres had lung function measured in 1991–93, when aged 20–44 years, and in 1998–2002. Smoking information was obtained from detailed questionnaires. Changes in lung function were analysed by change in smoking and weight, adjusted for age and height, in men and women separately and together with interaction terms.

Findings

Compared with those who had never smoked, decline in FEV1 was lower in male sustained quitters (mean difference 5·4 mL per year, 95% CI 1·7 to 9·1) and those who quit between surveys (2·5 mL, −1·9 to 7·0), and greater in smokers (−4·8 mL, −7·9 to −1·6). In women, estimates were 1·3 mL per year (−1·5 to 4·1), 2·8 mL (−0·8 to 6·3) and −5·1 mL (−7·5 to −2·8), respectively. These sex differences were not significant. FEV1 changed by −11·5 mL (−13·3 to −9·6) per kg weight gained in men, and by −3·7 mL per kg (−5·0 to −2·5) in women, which diminished the benefit of quitting by 38% in men, and by 17% in women.

Interpretation

Smoking cessation is beneficial for lung function, but maximum benefit needs control of weight gain, especially in men.

Introduction

A review of the effect of smoking cessation on outcomes including lung function made no mention of adverse effects of concomitant weight gain,1 although these could be substantial.2 Longitudinal studies that have assessed the relation of change in lung function to smoking cessation and change in body-mass index (BMI) have shown that the beneficial effect of smoking cessation outweighs the adverse effect of weight gain.3, 4, 5 The estimates of the weight gain contribution vary,5 which could in part be due to the different populations studied. Only one study was of a general population,5 another was of steelworkers,3 and the third was a randomised controlled trial of smokers with mild to moderate chronic obstructive pulmonary disease.4 Two studies showed that weight gain had a more deleterious effect on lung function in men than in women,4, 5 and the Lung Health study6 also showed a greater net beneficial effect of smoking cessation in women than in men. The only population study, which used data from the Health and Lifestyle Survey,5 included data for 3391 British men and women aged 18–73 years, who were followed up for 7 years. Although the independent effects of quitting smoking and weight gain were estimated, the total effect of quitting (ie, the effect net of weight gain) was not reported.

The full effect of quitting smoking in the general population is therefore not known, nor is whether the effect is consistent across countries. The European Community Respiratory Health Survey II (ECRHS II)7 was a multicentre follow-up study of participants in ECRHS I, which selected adults aged 20–44 years.8 We analysed change in lung function to estimate the net effect of smoking cessation and independent effects of smoking cessation and weight change, to show whether these differ between men and women, and to study heterogeneity of findings across much of western Europe.

Section snippets

Participants

Each survey had a self-completed postal questionnaire, stage 1, followed by stage 2, which included an administered questionnaire and measurement of spirometric lung function. Only data for the random sample selected for ECRHS I stage 2, undertaken in 1991–93,8 were included. Participants in ECRHS I stage 2 were eligible for ECRHS II. Most centres that participated in ECRHS I stage 2 took part in ECRHS II.7 Follow-up was from 1998 to 2002. Ethical approval was obtained for each centre from the

Results

A total of 14 632 people in the random sample in the 27 centres were eligible to take part in ECRHS II, of whom 12 417 had lung function measured at ECRHS I (figure 1). Details of response to ECRHS II stage 1 are given elsewhere.13 Of the 12 417, 7738 (62·3%) were traced and responded to the main questionnaire in ECRHS II, and 6654 had valid lung function with at least one valid measurement of FEV1 or FVC. Overall, slightly more eligible men (3484 of 6987, 49·9%) than women (3654 of 7645,

Discussion

Our study has documented the effect of both smoking cessation and weight change on lung function in a general population, and the full (net) effect of smoking cessation in the community. We have found a similar net effect of smoking cessation in men and women, but a greater decline in lung function due to weight gain in men.

There was some differential loss to follow-up, as in the few other longitudinal studies which have reported on such loss.14, 15 This loss is unlikely to greatly bias the

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