Strother H. Walker

A method for estimating the probability of occurrence of an event from dichotomous or polychotomous data is developed, using a recursive approach. The method in the dichotomous case is applied to the data of a 10-year prospective study of coronary disease. Other areas of application are briefly indicated.

Follow-up of the prevalence study of respiratory symptoms and chronic airway obstruction was performed after a 6- to 7-year interval. One hundred fifteen of 117 subjects (98%) originally labeled "abnormal" (chronic bronchitis or asthma by history, or ratio of 1-sec forced expiratory volume to forced vital capacity less than 60 per cent), and 111 of a random sample of 116 subjects (96%) originally labeled "normal" were traced. Nineteen patients were dead, 14 "abnormal" subjects, and 5 "normal" subjects (P less than 0.01). Eighty-eight of the originally labeled "abnormal" subjects and 91 of the random "normal" sample could be retested by spirometry. Subjects with lower initial ratios of 1-sec forced expiratory volume to forced vital capacity tended to lose more 1-sec forced expiratory volume and forced vital capacity. Early identification of respiratory symptoms and spirometric abnormalities may identify persons at increased risk of death who could benefit from appropriate therapy.

Well defined methods for comparing mean polynomial growth curves exist when subjects are measured at identical times, modeled with polynomials of identical degree and when multivariate normality of the measurements can be assumed. Relaxing these conditions creates problems solved here for the special case of a completely randomized design by developing a randomization test which is both practical and interval specific. The procedure is applied to longitudinal data from a study of human growth.

A study of the prevalence of chronic respiratory disease symptoms in a random sample comprising one fifth of the adult population of Glenwood Springs, Colorado was conducted in the spring of 1967. Standard methods were used that permitted comparison of results with certain other studies. The high prevalence of chronic bronchitis was found to be strongly related to smoking, particularly of cigarettes, and was independent of age, sex, or history of dust exposure at work. Chronic airway obstruction was found to be predominantly a disease of elderly male smokers and increased in frequency with increasing age after 49 years. Male smokers with a history of dust exposure at work had a higher rate of chronic airway obstruction than smokers without such a history. The prevalence of nonobstructive chronic bronchitis did not change significantly with age in men whereas that of combined chronic bronchitis and chronic airway obstruction increased. Chronic airway obstruction without bronchitis increased with age in men older than 49. It was uncommon in women, regard· less of smoking habits. Exertional dyspnea was related to heart disease, increasing age, female sex, and smoking, but it correlated most strongly with spirometric evidence of airway obstruction. Wheezing was more common in male and female cigarette smokers, and hemoptysis was more common in male cigarette smokers than in nonsmokers. In all studies with which comparison was made, chronic bronchitis was strongly associated with smoking, but significant interstudy variation in prevalence was found both among smokers and nonsmokers, so that other factors might be of importance. More limited comparisons of the preva· lence of chronic airway obstruction showed a consistent relationship of this condition to smoking in men but not in women.