Forced vital capacity paired with Framingham Risk Score for prediction of all-cause mortality

Abstract

Forced vital capacity (FVC) measures lung function and predicts coronary heart disease (CHD); whether it provides additive prediction over CHD risk factors has not been established. We examined whether FVC adds to the prediction of all-cause mortality provided by Framingham Risk Score (FRS) alone. We examined 5,485 (61.1 million projected) nonsmoking adults from the USA who were aged 20-79 yrs. Subjects were from the Third National Health and Nutrition Examination Survey, were without obstructive lung disease, had FVC measurements and had ≤ 12 yrs (mean 8.8 yrs) mortality follow-up. We performed Cox regression analysis to examine whether FVC and forced expiratory volume in 1 s (FEV(1)) (categorised as low ≤ 85% predicted, borderline 86-94% predicted and normal ≥ 95% predicted) within FRS groups (10-yr risk of cardiovascular disease low <10%, intermediate 10-20%, high 20%) predict mortality. Receiver operator characteristic analysis examined whether FVC and FEV(1) added to the prediction provided by FRS. Low-, intermediate- and high-risk FRS groups had 79.5% (n = 4,361), 10.1% (n = 555) and 10.4% (n = 569) persons, respectively. Only the intermediate FRS group showed a graded increase in mortality (10.7, 18.2 and 42.8% per 1,000 person-yrs from highest to lowest FVC categories, respectively); those with low FVC had an almost three-fold greater risk of mortality (hazard ratio 2.64; p<0.01) than those with normal FVC. FVC provided incremental additive value for predicting mortality in addition to FRS for only this group (area under curve 0.65 versus 0.58; p<0.05). Similar results were obtained for FEV(1). Evaluation of lung function may be useful to improve risk stratification in persons with intermediate CHD risk where it adds to prediction of mortality over global risk assessment.