Baseline characteristics of the participants.

Definition of abbreviations; PY pack-years, BMI body mass index, FVC forced vital capacity, FEV1forced expiratory volume in one second *Cough or sputum for more than three months within a year. Proportion is calculated after excluding 4,324 participants without answer. Values are represented as number (%), or mean ± standard deviation unless otherwise stated. Baseline characteristics of the participants.缩写定义：PY（pack-years，包-年）、BMI（body mass index，体重指数）、FVC（forced vital capacity，用力肺活量）、FEV1（forced expiratory volume in one second，一秒用力呼气容积） * 年度内咳嗽或咳痰症状持续超过三个月。相关占比经剔除4324名未作答参与者后计算得出。 除非另有说明，数据以例数（百分比）或均值±标准差表示。 参与者的基线特征。