Reduced subjective awareness of bronchoconstriction provoked by methacholine in elderly asthmatic and normal subjects as measured on a simple awareness scale

Abstract

Background: Asthma death rates are rising, with the greatest rise and highest death rates in old age. A reduced cardiovascular response in the elderly may lead to the underestimation by physicians of the severity of acute asthma attacks. This would be compounded if elderly patients had reduced awareness of bronchoconstriction.

Methods: Methacholine provoked bronchoconstriction was compared in 34 elderly (17 asthmatic, 17 normal; age 60-83, mean 68 years) and 33 young subjects (16 asthmatic, 17 normal; 20-46, mean 30 years). None were smokers. All underwent inhaled methacholine challenge by the Newcastle dosimeter method, monitored by maximal expiratory flow-volume loops (MEFVL). The endpoints were a 35% fall in forced expiratory flow at 50% vital capacity or cumulative inhalation of 6.4 mg methacholine. The one second forced expiratory volume (FEV1) was derived from MEFVL. After challenge and before bronchodilatation subjects graded awareness of respiratory discomfort from 1 (no symptoms) to 4 (pronounced symptoms needing immediate treatment).

Results: Despite a greater fall in FEV1 in elderly asthmatic patients (mean (SE) 27.4% (2.2%)) than in young asthmatic patients (21.5% (1.7%)) elderly patients were less aware of bronchoconstriction (awareness score 2.00 (SE 0.15) than young patients (3.06 (0.11)). Similar differences in awareness score were seen between elderly normal subjects (1.53 (0.17)) and young normal subjects (2.76 (0.22)), despite no difference in degree of bronchoconstriction.

Conclusions: Reduced awareness of moderate acute bronchoconstriction in old age may delay self referral in acute asthma and contribute to higher asthma mortality in the elderly.