No abstract

Bronchial responsiveness (BR) was assessed by the methacholine challenge test in 1,694 subjects from a sample of the general population (aged 8 to 73 yr) enrolled in a prospective epidemiologic study on the natural history of chronic obstructive pulmonary disease (COPD). Information on respiratory symptoms and risk factors for COPD were obtained with a standardized questionnaire. The provocative dose causing a 10%, 15%, and 20% decrease in FEV1 was reached in 939 (55%), 658 (39%), and 447 (26%) subjects, respectively, after the last cumulative dose of methacholine (i.e., 4.8 mg). The slope of the dose-response curve was also computed in order to attribute a parameter to subjects who did not reach the provocative dose. After natural log transformation, the slope (Ln Slope) of the curve showed a significant association with the degree of airway obstruction, as assessed by FEV1% predicted, FEV1/VC%, and FEV1/FVC%. Therefore, relationships between BR, sex, age, and smoking were evaluated after adjustments for the initial airway caliber (FEV1, FEV1 adjusted for height, and FEV1/VC%). Females showed significantly higher values of Ln Slope than did males after adjustments were made for baseline lung function. In males, higher BR was observed in childhood-adolescence age groups and at older ages, while in females a higher level of BR was observed during childhood. Significantly higher Ln Slope values were found for females who currently smoked than for non- and ex-smokers. No difference was observed in males in relation to smoking habit. (ABSTRACT TRUNCATED AT 250 WORDS)

We derived reference values for slow vital capacity (VC) and flow-volume curve indexes (FVC, FEV(1), and flows) from the 1,185 tracings provided by 1,039 "normal" subjects who participated in one or both cross-sectional surveys of the Po River Delta study in 1980-1982 and in 1988-1991. Definition of "normal" was based on negative answers to questions on respiratory symptoms/diseases or recent infections, current/past tobacco smoking, and work exposure to noxious agents. Reference equations were derived separately by sex as linear regressions of body mass index (BMI = weight/height(2)), BMI-squared, height, height-squared, and age. Age entered all the models by natural cubic splines using two break points, except for the ratios FEV(1)/VC and FEV(1)/FVC. Random effects models were applied to adjust for the potential intrasubject correlation. BMI, along with height and age, appeared to be an important predictor, which was significantly associated with VC, FEV(1), FVC, FEV(1)/FVC, and PEF in both sexes, and with FEV(1)/VC and FEF(25-75) in females. Natural cubic splines provided smooth reference equation curves (no "jumps" or "angled points") over the entire age span, differently from the conventional reference equations. Thus, we recommend the use of smooth continuous equations for predicting lung function indexes, along with the inclusion of BMI in the equations.