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Flow chart of study population.COPD denotes chronic obstructive pulmonary disease. Missing data is in one or more of the following variables: height, ethnicity, educational attainment, income, Townsend deprivation index, smoking history, spirometry measurements, maternal COPD history, paternal COPD history, age at menarche, menopause status, age at natural menopause, parity, oral contraception use, hormone replacement therapy use or gynaecological surgery history.
