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RATIONALE: The term 'pre-COPD' refers to individuals at high-risk of developing Chronic Obstructive Pulmonary Disease (COPD) who do not meet conventional spirometric criteria for airflow obstruction. New approaches to identifying these individuals are needed, particularly in younger populations. OBJECTIVE: To determine whether lung function thresholds and respiratory symptoms can be used to identify individuals at-risk of developing COPD. METHODS: The Tasmanian Longitudinal Health Study is a population-based cohort first studied in 1968 (age 7). Respiratory symptoms, pre- and post-bronchodilator (BD) spirometry, diffusing capacity and static lung volumes were measured on a subgroup at age 45, and incidence of COPD was assessed at age 53. For each lung function measure, z-scores were calculated using Global Lung Initiative references. The optimal threshold for best discrimination of COPD incidence was determined by the unweighted Youden Index. MEASUREMENTS AND MAIN RESULTS: Among 801 participants who did not have COPD at age 45, the optimal threshold for COPD incidence by age 53 was pre-BD FEV1/FVC z-score < -1.264, corresponding to the lowest 10th percentile. Those below this threshold had 36-fold increased risk of developing COPD over an eight-year follow-up period (RR 35.8, 95%CI 8.88 to 144), corresponding to a risk difference of +16.4% (95%CI 3.7-67.4). The sensitivity was 88% and specificity 87%. Positive and negative likelihood ratios were 6.79 and 0.14, respectively. Respiratory symptoms, post-BD spirometry, diffusing capacity and static lung volumes did not improve on the classification achieved by pre-BD FEV1/FVC alone. CONCLUSION: Our findings support the inclusion of pre-BD spirometry in the physiological definition of pre-COPD and indicate that pre-BD FEV1/FVC at the 10th percentile accurately identifies individuals at high-risk of developing COPD in community-based settings.
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BACKGROUND: Residing in greener areas has several health benefits, but no study to date has examined the effects of greenness on metabolic syndrome (MetS). We aimed to assess associations between residential greenness and MetS prevalence in China, and to explore whether air pollution and physical activity mediated any observed associations. METHODS: We analyzed data from 15,477 adults who participated in the 33 Communities Chinese Health Study during 2009. We defined MetS according to standard guidelines for Chinese populations. Residential greenness was estimated using the Normalized Difference Vegetation Index (NDVI), the Soil Adjusted Vegetation Index (SAVI), and the Vegetation Continuous Field (VCF). We used generalized linear mixed models to assess the associations between greenness and MetS, and mediation analyses to explore potential mechanisms underlying the associations. RESULTS: Higher greenness levels were associated with lower odds of MetS [e.g., for every interquartile range increase of NDVI500-m, SAVI500-m, and VCF500-m, the adjusted odds ratio of MetS was 0.81 (95% confidence interval: 0.70-0.93), 0.80 (95% confidence interval: 0.69-0.93), and 0.91 (95% confidence interval: 0.83-1.00), respectively]. The direction and the magnitude of the associations persisted in several sensitivity analyses. Stratified analyses showed that age and household income modified the associations, with greater effect estimates observed in participants younger than 65 years old or those with higher household income. Particulate matter with an aerodynamic diameter ≤10 µm, nitrogen dioxide, and ozone mediated 2.1-20.3% of the associations between greenness and MetS; no evidence of mediation was observed for physical activity. CONCLUSIONS: Our findings suggest a beneficial association for residential greenness and MetS in Chinese urban dwellers, especially for participants younger than 65 years old and those with higher household income. Particulate matter with an aerodynamic diameter ≤10 µm, nitrogen dioxide and ozone, but not physical activity, may only partially mediate the association.