BACKGROUND: The presence of restrictive lung disease has classically required the measure of total lung capacity to document `true' restriction, which has limited its detection in large population-based studies.

METHODS: We used spirometric data to classify people with restricted spirometry (forced expiratory volume in 1 second [FEV1]/forced vital capacity ≥ 0.70 and FEV1 < 80% predicted) in the Burden of Lung Disease (BOLD) Study and determined the relation between this finding and demographic factors and the presence of chronic diseases, including diabetes mellitus, hypertension and cardiovascular disease.

RESULTS: Overall, we found that 11.7% of men (546/4664) and 16.4% of women (836/5098) had restricted spirometry. Prevalence varied widely by site, from a low of 4.2% among males in Sydney, Australia, to a high of 48.7% among females in Manila, The Philippines. Compared to people with normal lung function, those with restricted spirometry had a higher prevalence of diabetes (12.2% vs. 4.6%), heart disease (15.0% vs. 7.7%) and hypertension (38.8% vs. 22.8%).

CONCLUSIONS: Restricted spirometry is a common finding in population studies. Additional research is needed to better define and describe the mechanisms that lead to restricted spirometry and potential interventions.