The association between metabolic syndrome and restrictive ventilatory dysfunction in older persons

Background. The restrictive, but not the obstructive respiratory dysfunction, is associated with an increased risk of developing type 2 diabetes mellitus. Our aim was to verify in an elderly nondiabetic population whether a restrictive respiratory pattern was associated with a higher prevalence of metabolic syndrome and increased insulin resistance than were obstructive and normal respiratory patterns. Methods. We performed a cross-sectional study of 159 consecutive nondiabetic elderly persons attending two social centers. According to their spirometric pattern, volunteers were classified into the following categories: normal spirometry, obstructive (forced expiratory volume in 1 second/forced vital capacity < 0.70), and restrictive pattern (forced vital capacity < 80% predicted, forced expiratory volume in 1 second/forced vital capacity >= 0.70). Independent correlates of the metabolic syndrome were identified. Results. The prevalence of metabolic syndrome was higher in restrictive (56%) than in both normal (21.4%, p =.001) and obstructive volunteers (12.9%, p =.001). Insulin resistance, as assessed by the log transformation of the HOmeostasis Model Assessment (HOMA), was higher in restrictive than in obstructive and normal volunteers (1 +/- 0.6 vs 0.3 +/- 0.6 and 0.5 +/- 0.5, p <.001). Restriction was an independent correlate of metabolic syndrome, also after adjustment for waist circumference and body mass index (odds ratio = 3.23, 95% confidence interval, 1.23-8.48; p =.01). Conclusion. Restrictive, but not obstructive respiratory pattern, is associated with metabolic syndrome and insulin resistance, and does not only reflect a limitation of ventilation due to visceral obesity. Metabolic abnormalities likely mediate cardiovascular risk in patients with restrictive respiratory impairment.