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Variation in “normal values” of forced vital capacity (FVC) and ratio of one-second Forced Expiratory Volume (FEV1)/FVC between 42 Burden of Obstructive Lung Disease (BOLD) sites

Background: “Normal” lung function is generally defined in relation to the values found in a symptom free, non-smoking population, after adjustment for age and height. We investigated these values for >12,000 adults aged > 40 living in 42 BOLD sites. Methods: The sites were grouped into 4 “regions”, Europe (including US, Canada and Australia), Near East (including North Africa and Central Asia), Africa (including Caribbean) and Far East (including South, South East and East Asia). FVC and FEV1/FVC in never-smokers without respiratory symptoms or diagnoses were regressed against age, age2, and height2 within each centre. Coefficients were compared between sites and regions. Results: FVC was best described by age and height2. Both coefficients varied between regions with less variation within regions, but significant variation in the coefficient for height2 within both Africa and the Far East. Compared with Europe, after adjusting for age and height, values for men/women were on average 12%/8% lower in the Near East, 14%/20% lower in Africa and 24%/25% lower in the Far East, but this value was highly variable within all regions except Europe. The FEV1/FVC ratio varied weakly with both age and height2. Though the value adjusted for age and height varied significantly this variation was not substantial (0.84 in Europe and Far East, 0.85 in the Near East and Africa). This value varied significantly within Africa. Conclusion: There is significant variation in the associations of FVC with age, height and by region, but there is also significant variation within regions.