Normal Range of Methacholine Responsiveness in Relation to Prechallenge Pulmonary Function: Methods
The Normative Aging Study is a longitudinal cohort study of health and aging established at the Veterans Administration’s Outpatient Clinic in Boston in 1963. Volunteers were recruited by advertisement and accepted into the study only if initial health screening revealed no evidence of chronic diseases including asthma, sinusitis, hypertension, or heart disease. The initial cohort consisted of 2,280 men between the ages of 21 and 80 years. Since entry into the study, subjects have reported periodically for comprehensive health assessment, including medical history, physical examination, spirometry, electrocardiogram, chest radiograph, and blood tests. Beginning in 1984, subjects have completed respiratory illness and symptom questionnaires and have undergone methacholine challenge testing every 3 years. As described in detail below, the present analysis is based on 1,410 subjects who reported for at least one examination between April 1984 and June 1990. canadian health&care mall
A self-completed respiratory illness and symptom questionnaire adapted from the ATS-DLD questionnaire was completed by all subjects within 1 week prior to methacholine challenge testing. “Current asthma” was defined as an affirmative response to the questions “have you ever had asthma?” and “do you still have it?” “Former asthma” was defined as an affirmative response to the former question with a negative response to the latter question. “Episodic wheeze with dyspnea” was defined as an affirmative response to the question “have you ever had attacks of wheezing with shortness of breath?” “Persistent wheeze” was defined as an affirmative response to the question “have you ever had wheezing in your chest?” which included either “most days and nights” or both “with colds” and “occasionally apart from colds.” A subject was considered asymptomatic if he denied any history of asthma, wheezing, usual cough, usual phlegm, chronic bronchitis, or shortness of breath sufficient to cause stopping to catch breath. A subject was considered a lifetime nonsmoker if he denied smoking at least one cigarette per day at present and had smoked less than 20 packs in his lifetime.
Baseline (prechallenge) spirometry was performed in the standing position, wearing noseclips, with the use of a water-filled survey spirometer (Collins 8-L, Warren Collins, Inc, Braintree, Mass) in accordance with published guidelines. The FVC and FEV,, corrected to BTPS, were calculated by a microprocessor (Eagle II, Warren Collins Inc, Braintree, Mass).