PN Lee Statistics and Computing Ltd, Surrey, UK.
BMC Med. 2010 Dec 14;8:84. doi: 10.1186/1741-7015-8-84.
The rate of forced expiratory volume in 1 second (FEV1) decline ("beta") is a marker of chronic obstructive pulmonary disease risk. The reduction in beta after quitting smoking is an upper limit for the reduction achievable from switching to novel nicotine delivery products. We review available evidence to estimate this reduction and quantify the relationship of smoking to beta.
Studies were identified, in healthy individuals or patients with respiratory disease, that provided data on beta over at least 2 years of follow-up, separately for those who gave up smoking and other smoking groups. Publications to June 2010 were considered. Independent beta estimates were derived for four main smoking groups: never smokers, ex-smokers (before baseline), quitters (during follow-up) and continuing smokers. Unweighted and inverse variance-weighted regression analyses compared betas in the smoking groups, and in continuing smokers by amount smoked, and estimated whether beta or beta differences between smoking groups varied by age, sex and other factors.
Forty-seven studies had relevant data, 28 for both sexes and 19 for males. Sixteen studies started before 1970. Mean follow-up was 11 years. On the basis of weighted analysis of 303 betas for the four smoking groups, never smokers had a beta 10.8 mL/yr (95% confidence interval (CI), 8.9 to 12.8) less than continuing smokers. Betas for ex-smokers were 12.4 mL/yr (95% CI, 10.1 to 14.7) less than for continuing smokers, and for quitters, 8.5 mL/yr (95% CI, 5.6 to 11.4) less. These betas were similar to that for never smokers. In continuing smokers, beta increased 0.33 mL/yr per cigarette/day. Beta differences between continuing smokers and those who gave up were greater in patients with respiratory disease or with reduced baseline lung function, but were not clearly related to age or sex.
The available data have numerous limitations, but clearly show that continuing smokers have a beta that is dose-related and over 10 mL/yr greater than in never smokers, ex-smokers or quitters. The greater decline in those with respiratory disease or reduced lung function is consistent with some smokers having a more rapid rate of FEV1 decline. These results help in designing studies comparing continuing smokers of conventional cigarettes and switchers to novel products.
1 秒用力呼气容积（FEV1）下降率（“β”）是慢性阻塞性肺疾病风险的标志物。戒烟后β的下降是通过改用新型尼古丁输送产品可实现的下降幅度的上限。我们回顾了现有证据，以估计这种下降幅度，并量化吸烟与β的关系。
我们确定了在至少 2 年随访期间分别为戒烟者和其他吸烟组提供β数据的研究，这些研究在健康个体或患有呼吸道疾病的患者中进行。考虑了截至 2010 年 6 月的出版物。为四个主要吸烟组（从不吸烟者、戒烟前（基线前）的前吸烟者、戒烟者（随访期间）和持续吸烟者）得出了独立的β估计值。非加权和倒数方差加权回归分析比较了吸烟组的β值，以及按吸烟量划分的持续吸烟者的β值，并估计了β值或吸烟组之间的β值差异是否因年龄、性别和其他因素而异。
47 项研究有相关数据，其中 28 项为男女共同研究，19 项为男性研究。16 项研究开始于 1970 年之前。平均随访时间为 11 年。基于对四个吸烟组的 303 个β值的加权分析，从不吸烟者的β值比持续吸烟者低 10.8 mL/yr（95%置信区间（CI），8.9 至 12.8）。前吸烟者的β值比持续吸烟者低 12.4 mL/yr（95%CI，10.1 至 14.7），戒烟者的β值低 8.5 mL/yr（95%CI，5.6 至 11.4）。这些β值与从不吸烟者相似。在持续吸烟者中，β值每增加 1 支/天增加 0.33 mL/yr。与戒烟者相比，持续吸烟者的β值差异在患有呼吸道疾病或肺功能降低的患者中更大，但与年龄或性别无明显关系。
现有数据存在诸多局限性，但清楚地表明，持续吸烟者的β值与吸烟量有关，比从不吸烟者、前吸烟者或戒烟者高出 10 毫升/年以上。呼吸道疾病或肺功能降低患者的下降幅度更大，这与一些吸烟者的 FEV1 下降速度更快一致。这些结果有助于设计比较传统香烟的持续吸烟者和改用新型产品的吸烟者的研究。
