Abstract
BackgroundData for the U.S adult population from the National Health and Nutrition Examination Survey (NHANES) were used to evaluate risk factors for a restrictive pattern on spirometry and estimate the change in its prevalence from the 1988–1994 to 2007–2010 sampling periods. Several previous epidemiologic studies used the Global Initiative for Chronic Obstructive Lung Disease fixed forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) > 0.70 criteria for classifying restrictive pattern rather than the age-defined American Thoracic Society (ATS)/European Respiratory Society (ERS) lower limit of normal (LLN) criteria, which may lead to misclassification.MethodsSpirometry measurements from NHANES data for the 1988–1994 and 2007–2010 periods were analyzed to estimate the age-standardized prevalence of a restrictive pattern on spirometry and the change in prevalence over time for adults aged 20–79. A restrictive pattern was defined based on ATS/ERS LLN criteria as FEV1/FVC > LLN and FVC < LLN, and a moderate to more severe restrictive pattern was further evaluated using FEV1 < 70% predicted. The associations between demographic and other individual risk factors for restrictive lung impairment were examined using multivariable logistic regression models for the two consecutive time periods.ResultsThe overall age-standardized prevalence of restrictive pattern decreased significantly from 7.2% (1988–1994) to 5.4% (2007–2010) (p = 0.0013). The prevalence of moderate to more severe restrictive pattern also decreased significantly from 2.0% to 1.4% (p = 0.023). Factors positively associated with restrictive pattern on spirometry included age, female sex, white race, lower education, former and current smoking, and comorbidities including doctor-diagnosed cardiovascular disease, doctor-diagnosed diabetes, and abdominal obesity.ConclusionsThe overall prevalence of restrictive pattern and moderate to more severe restrictive pattern decreased between the 1988–1994 and 2007–2010 survey periods despite a population increase in the proportion of comorbidities associated with restrictive pattern (i.e. diabetes and abdominal obesity). This suggests a decline in individual risk factors for restrictive pattern and a need for future research.
Highlights
Data for the U.S adult population from the National Health and Nutrition Examination Survey (NHANES) were used to evaluate risk factors for a restrictive pattern on spirometry and estimate the change in its prevalence from the 1988–1994 to 2007–2010 sampling periods
The spirometry methods and equipment for the two periods differed by the following: 1) the flow-volume curve was displayed by the spirometry software for inspection by the technician in 1988–1994, while both the volume-time and flow-volume curves were available for inspection in 2007–2010; 2) the minimum number of acceptable maneuvers performed per test session was five (1988–1994) and three (2007–2010); 3) the test session repeatability requirement changed from 200 ml (1988–1994) to 150 ml (2007–2010); 4) the 2007–2010 survey included annual refresher training and bi-weekly, as opposed to monthly, quality control reports by the National Institute for Occupational Safety and Health [18,19]
This study estimated the age-standardized prevalence of and risk factors associated with a restrictive pattern on spirometry in two population samples of U.S adults surveyed approximately two decades apart
Summary
Data for the U.S adult population from the National Health and Nutrition Examination Survey (NHANES) were used to evaluate risk factors for a restrictive pattern on spirometry and estimate the change in its prevalence from the 1988–1994 to 2007–2010 sampling periods. Restrictive pattern on spirometry is associated with functional limitations, fair or poor self-reported health status [1], reduced physical performance and physical impairment in older adults [2], and increased morbidity and mortality [3,4,5,6]. National and global adult population-based epidemiologic studies report increased risk of a restrictive pattern on spirometry among older age groups [3,5,6], females [3,6], African American and other race/ethnicity groups [5], and smokers [3,5,6]. Exposure to substances found in the workplace including asbestos, silica, coal mine dust, and other organic and inorganic dusts are known to cause fibrotic tissue changes associated with restriction [11]
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