Spirometrically-defined restrictive ventilatory defect: population variability and individual determinants.

Background: A spirometrically-defined restrictive ventilatory defect is a common finding when performing spirometry.

Aims: We aimed to determine the frequency, geographical variation, individual consequences, and 'severity' of the restrictive ventilatory defect.

Methods: A population-based study was conducted in Spain. The response rate from 11 participating centres was 88.9%, totalling 3,802 participants. A restrictive ventilatory defect was defined according to pre-bronchodilator spirometry as forced expiratory volume in 1s/forced vital capacity (FEV1/FVC) >0.70 and a predicted FVC <80%, in accordance with current American Thoracic Society/European Respiratory Society guidelines.

Results: The prevalence of a restrictive ventilatory defect was 12.7% (95% CI 9.7% to 15.7%), with the highest in Seville (19.4%) and Burgos (18.5%) and the lowest in Oviedo (5.2%) and Madrid-La Princesa (5.7%) (p<0.000). Although most of the participants (97.1%) with a restrictive ventilatory defect were objectively considered 'mild' by spirometry (%predicted FVC 50-80%), they reported more phlegm, dyspnoea, and wheezing than healthy control participants (p<0.000), and scored worse in all St George's Respiratory Questionnaire domains of quality of life and activities of daily living (p<0.000). Interestingly, they scored similarly to participants with chronic obstructive pulmonary disease (COPD) in both (p=0.102 and p=0.217). In a multivariate analysis, older age, male gender, heavy smoking, low education, and high body mass index were independently associated with having a restrictive ventilatory defect.

Conclusions: A restrictive ventilatory defect in spirometry is a common finding (12.7%) with a highly variable geographical distribution (range 3.7) whose population burden is important in terms of quality of life and activities of daily living and similar to that of an obstructive pattern compatible with COPD.