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Background Population studies that assess lung function usually exclude results of individuals with poor-quality measurements, which often means excluding many subjects. Impaired cognition is frequently associated with poor-quality spirometry; excluding such subjects may introduce a selection bias in studies with lung function as either outcome or exposure. We investigated the association between poor-quality spirometry and impaired cognitive function and whether poor-quality spirometry is associated with future mortality risk independently of cognitive function. Methods We used data from a prospective cohort in three Central and Eastern European countries; 12,087 individuals aged 45–75 years (54% females) with complete information on variables of interest were included. Standard memory, verbal fluency, and executive cognitive domain tests were converted into latent variable z-scores and divided into quartiles. Spirometry tests were classified into two categories based on repeatability criteria: good- (71%) vs. poor-quality spirometry (29% of participants). Those with good-quality spirometry were further classified, using forced vital capacity (FVC) and forced expiratory volume in the first second (FEV 1 ), as healthy spirometry (63%) or impaired spirometry (8%). Multinomial logistic regression was used to assess the association between poor-quality spirometry and cognitive function, and a Cox proportional regression was used to analyze the risk of total mortality over a 17-year follow-up. Results After controlling for a range of covariates, higher cognitive function predicted lower odds of poor-quality spirometry. In the highest cognitive function quartile, compared with the lowest quartile, the odds ratio of poor-quality spirometry was 0.82 (95%CI: 0.72–0.92). Impaired spirometry was associated with higher mortality risk even after adjusting for cognition (adjusted hazard ratio 1.63, 95%CI: 1.45–1.84), but mortality risk was similar in subjects with poor- vs. good-quality (HR 1.02, 95%CI: 0.93–1.10). Conclusion Higher cognitive function was associated with a lower risk of poor-quality spirometry. The lack of independent association of poor-quality spirometry with mortality suggests that excluding poor-quality spirometry measurements from analyses is unlikely to introduce a major bias. However, discarding poor-quality spirometry from epidemiological analyses might imply the exclusion of vulnerable subjects. These findings should be confirmed in future studies representing other populations.

BackgroundSocial differences in lung functioning have been reported, but the role of socioeconomic position (SEP) at different stages of life is less well understood, particularly in Central and Eastern Europe. This study addressed this question.MethodsThe analysis included 10 160 individuals aged 45–70 years from the Czech Republic, Poland and Lithuania. Lung function was either normal if values of forced expiratory volume in the first second divided by forced vital capacity (FEV1/FVC) and FVC were higher than the lower limit of normality or impaired if otherwise. SEP at three stages of life was assessed using maternal education (childhood), participant’s education (young adulthood), and current ability to pay for food, clothes and bills (late adulthood). SEP measures were dichotomised as advantaged versus disadvantaged. The associations between impaired lung function and life-course SEP were estimated by logistic regression.ResultsDisadvantaged SEP in young and late adulthood had higher odds of impaired lung function. In young adulthood, age-adjusted ORs were 1.26 (95% CI 1.06 to 1.49) in men and 1.56 (95% CI 1.29 to 1.88) in women, while in late adulthood, the ORs were 1.15 (95% CI 0.99 to 1.34) in men and 1.26 (95% CI 1.09 to 1.46) in women. Men and women disadvantaged at all three stages of life had ORs of 1.42 (95% CI 1.06 to 1.91) and 1.83 (95% CI 1.32 to 2.52), respectively, compared with those always advantaged. Smoking substantially attenuated the ORs in men but not in women.ConclusionReducing socioeconomic inequalities in young and late adulthood may contribute to reducing the risk of impaired lung function in late adulthood.