Bronchial responsiveness, spirometry and mortality in a cohort of adults

Prospective population studies have reported that pulmonary function, measured by forced expiratory volume in one second (FEV(1)), is an independent predictor for mortality. Besides, several studies found that death from all causes is higher in asthmatics than in non-asthmatics. However, none of these studies examined whether bronchial hyperresponsiveness (BHR), one of the key features in asthma, can be used as a predictor for mortality. Thus, the aim of this study was to analyze the association between BHR, FEV(1), and all-cause mortality in a population-based cohort of adults.

Within the cross-sectional survey ECRHS-I Erfurt (1990-1992), 1162 adults aged 20-65 years performed lung function tests, including spirometry and BHR testing by methacholine inhalation up to a cumulative dose of 2 mg. BHR was assessed from the methacholine dose nebulized at ≥ 20% fall of FEV(1). After circa 20 years of follow-up, the association between baseline lung function, BHR, and mortality was investigated.

A total of 85 individuals (7.3%) died during a mean follow-up period of 17.4 years (SD = 2.4). FEV(1), but not forced vital capacity (FVC), was a predictor for mortality. In men, BHR increased the mortality risk (OR = 2.6, 95% CI: 1.3-5.3; adjusted for age and BMI). Additional adjustment for asthma did not change the results (OR = 2.4, 95% CI: 1.2-5.0). However, after an additional adjustment for pack years of cigarette smoking or airway obstruction, the association was not statistically significant anymore (OR = 1.8, 95% CI: 0.8-4.0, OR = 1.9, 95% CI: 0.9-4.3, respectively).

BHR was associated with an increased mortality risk in men. Potential explanatory factors for this association are cigarette smoking, chronic obstructive pulmonary disease (COPD), or asthma. Thus, BHR might be an indirect predictor for all-cause mortality. FEV(1) was an independent predictor for all-cause mortality.