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Global differences in lung function by region (PURE): an international, community-based prospective study

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Summary

Background

Despite the rising burden of chronic respiratory diseases, global data for lung function are not available. We investigated global variation in lung function in healthy populations by region to establish whether regional factors contribute to lung function.

Methods

In an international, community-based prospective study, we enrolled individuals from communities in 17 countries between Jan 1, 2005, and Dec 31, 2009 (except for in Karnataka, India, where enrolment began on Jan 1, 2003). Trained local staff obtained data from participants with interview-based questionnaires, measured weight and height, and recorded forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC). We analysed data from participants 130–190 cm tall and aged 34–80 years who had a 5 pack-year smoking history or less, who were not affected by specified disorders and were not pregnant, and for whom we had at least two FEV1 and FVC measurements that did not vary by more than 200 mL. We divided the countries into seven socioeconomic and geographical regions: south Asia (India, Bangladesh, and Pakistan), east Asia (China), southeast Asia (Malaysia), sub-Saharan Africa (South Africa and Zimbabwe), South America (Argentina, Brazil, Colombia, and Chile), the Middle East (Iran, United Arab Emirates, and Turkey), and North America or Europe (Canada, Sweden, and Poland). Data were analysed with non-linear regression to model height, age, sex, and region.

Findings

153 996 individuals were enrolled from 628 communities. Data from 38 517 asymptomatic, healthy non-smokers (25 614 women; 12 903 men) were analysed. For all regions, lung function increased with height non-linearly, decreased with age, and was proportionately higher in men than women. The quantitative effect of height, age, and sex on lung function differed by region. Compared with North America or Europe, FEV1 adjusted for height, age, and sex was 31·3% (95% CI 30·8–31·8%) lower in south Asia, 24·2% (23·5–24·9%) lower in southeast Asia, 12·8% (12·4–13·4%) lower in east Asia, 20·9% (19·9–22·0%) lower in sub-Saharan Africa, 5·7% (5·1–6·4%) lower in South America, and 11·2% (10·6–11·8%) lower in the Middle East. We recorded similar but larger differences in FVC. The differences were not accounted for by variation in weight, urban versus rural location, and education level between regions.

Interpretation

Lung function differs substantially between regions of the world. These large differences are not explained by factors investigated in this study; the contribution of socioeconomic, genetic, and environmental factors and their interactions with lung function and lung health need further clarification.

Funding

Full funding sources listed at end of the paper (see Acknowledgments).

Introduction

The global rise in disease burden from chronic respiratory diseases1 means that more information is needed about global lung health, particularly factors that adversely affect lung function.2 Differences in lung function between ethnic groups have previously been investigated, but generally within one country or region.3 The most widely reported comparisons of lung function (forced expiratory volume in 1 s [FEV1] and forced vital capacity [FVC]) are between white people and African Americans (decrease of 10–15%4, 5) and between white people and individuals of Asian origin (decrease of 6–12%6, 7). Few data are available for other ethnic groups and populations in different geographical regions with vastly different socioeconomic and environmental exposures that could affect lung function.8

Our aim was to document the risk factors for chronic respiratory disease burden in adults globally. We deliberately oversampled countries of low to middle income, where the disease burden is high9 and expected to rise further; little information about lung function and lung health is available for these regions. We postulated that, after adjustment for height, age, and sex, substantial global differences in lung function would be recorded, which would be a result of the complex interactions between genes and environment for each region. These differences could contribute to the baseline population risk for chronic respiratory disease and the global disparity in disease burden.

Section snippets

Study design and participants

In the international, community-based prospective Population Rural Urban Epidemiology (PURE) study, we enrolled individuals aged 34–80 years from 628 urban and rural communities in 17 countries across five continents. Enrolment occurred between Jan 1, 2005, and Dec 31, 2009, except in Karnataka, India, where it began on Jan 1, 2003.

Details of the enumeration and recruitment methods are provided in the appendix and have been reported elsewhere.10 We used a multistage, convenience-sampled survey;

Results

153 996 individuals were enrolled from the 628 communities (figure 1). The countries with the highest numbers of participants were China and India (table 1). The proportion of unacceptable data was highest for South America and lowest for North America or Europe (table 2). The large amount of unacceptable data was not associated with low unadjusted lung function measurements (table 2). Healthy individuals excluded because of unacceptable data had similar baseline characteristics to individuals

Discussion

To our knowledge, we have provided the first large-scale assessment of global variation in lung function in asymptomatic non-smokers in different regions of the world (panel). We reported a significant and substantial difference in lung function between regions, with North America and Europe having the highest lung function and south Asia the lowest. These differences are not explained by variation in distribution of height, age, sex, weight, urban versus rural settings, or education levels.

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