Peak flow lability: association with asthma and spirometry in an older cohort.

OBJECTIVE To determine the success rate and correlates of ambulatory peak expiratory flow (PEF) monitoring in an epidemiologic study. DESIGN An observational survey. SETTING Several communities in California. PARTICIPANTS We studied 1,223 nonsmoking men and women (mean age, 66 years) from an established cohort. OUTCOME MEASURES A standard respiratory symptoms and diagnoses questionnaire, spirometry before and after bronchodilator, and a diary of PEF recorded four times per day for 7 days at home. RESULTS A physician diagnosis of asthma was reported in 8.6% of the women and 9.4% of the men. Of those who agreed to complete PEF diaries at home, 87% successfully provided a valid measure of PEF lability. The mean PEF lability from those with asthma was significantly higher than the others (12.0% vs 8.9% in women and 10.2% vs 8.1% in men). Independent correlates of higher PEF lability included asthma, wheezing symptoms, airways obstruction by spirometry, older age, and male gender. CONCLUSIONS Middle-aged and elderly persons are largely successful at providing a measure of PEF lability at home. In nonsmoking adults living in California, increased PEF lability is correlated with asthma, wheezing, airways obstruction, and older age, validating its use in epidemiology studies as an index of airways hyperreactivity.