Table 1 Summary of population-based studies estimating prevalence of small airways obstruction
Author, year | Study design | Population | Sample size | Age (years) | Sex | Spirometry Parameter(s) used to define SAO | Definition of abnormal result | Prevalence estimate(s) for SAO | Study quality (NOS) |
|---|---|---|---|---|---|---|---|---|---|
Detels et al. 1979 [29] | Cross-sectional | Burbank and Lancaster, California, USA White (94%); black (1%); Spanish-surnamed (4%); other (1%) | N = 7974 | 18–65 +  | F = 4126 (51.7%) | FEF25–75 | < 75% predicted | > 18 years only Pre BD 21.4%# | Fair |
Wipf et al. 1982 [35] | Cohort Baseline and at 5 years follow-up | Geneva, Switzerland Current, former and never smokers | N = 272 | 18–50 +  | F = 112, (41.2%) | FEF25–75/VC | FEF25–75/VC < FEV1/VC | Pre BD Baseline: 32.3% | Fair |
Marazzini et al. 1989 [32] | Cohort Baseline and 6 years | Italy, White-collar workers Smokers and non-smokers | N = 85 | Mean (SD): 41.25 (7.4) | M = 85 (100%) | FEF25-75, FEF25 and CC | One of: FEF25–75 < 60%, FEF25 < 65% CC > 130% predicted FEV1 and VC > 80% predicted | Pre BD Baseline: 45.9%# | Fair |
Cullinan et al. 1997 [23] | Cross-sectional | Bhopal India Site of Union Carbide gas leak Never and ever smokers | Spirometry: N = 74 Total: N = 454 | Mean (SD): 35.5 (3.2) | F = 44 (59.6%) | FEF25-75 |  < Lowest quartile (< 67% predicted) | Pre BD 25.7%# | fair |
Nemoto et al. 2011 [14] | Cross-sectional | Takahata Japan, participants of an annual health check Never and ever smokers | N = 2917 | 40–90 | F = 1592 (54.6%) | FEF50/FEF25 |  > 4.0 | Pre BD 36.5% | Fair |
Lam et al. 2012 [40] | Cross-sectional | Hong Kong Chinese Smokers only | N = 525 | 18–60 +  | M = 525 (100%) | FEV3/FVC |  < LLN | Pre BD 18.1% | Fair |
Chen et al. 2013 [38] | Nested case–control, with prevalence of SAO estimated from larger cohort | Moss Green, Huangqi Peninsula, Fujian, China Current former and never smokers | N = 2873 SAO: N = 216 | Median (IQR): 50.5 (42–59) 50.5 (42–58) | F = 121 (56%) F = 240 (56%) | FEF50 |  < 70% predicted | Pre BD 7.5% | Fair |
Hansen et al. 2015 [12] | Cross-sectional | USA, NHANES-3 data Current smokers | N = 3508 | 20–79.9 | F = 1571 (44.7%) | FEV3/FVC FEV3/FEV6 | < LLN < LLN | Pre BD 16.3% 16.6% | Fair |
Johns et al. 2017 [42] | Cross-sectional Post BD only | BOLD study, Victoria and Tasmania, Australia Never and ever smokers | N = 890 | Mean (SD): 58.7 (10.8) | F = 466 (52.4%) | FEF25-75 Central concavity Peripheral | FEV1/FVC > LLN < LLN > ULN > ULN | Post BD 5.4% 7.5% 9.8% | Fair |
Xiao et al. 2020 [13] | Cross-sectional | CPH study, mainland China Covering all geographical regions Current, former and never smokers | N = 50,479 | Mean (SD) 49.3 (13.8) | F = 29,213 (57.9%) | FEF25–75, FEF50 and FEF75 FEF25–75 FEF50 FEV3/FVC | 2/3 < 65% predicted < LLN < 70% predicted < LLN With: FEV1 > 80% and FEV1/FVC > 0.7 | Pre BD 28.5% Post BD 13.3% Pre BD: 26.9% Pre BD: 36.5% Pre BD: 13.9% | Good |