Predictors of longitudinal change in diffusing capacity over 8 years.

Low single-breath diffusing capacity (DL(CO)) values are associated with anatomic emphysema, but the predictors of longitudinal change in DL(CO) over many years are unknown. Study subjects were adult participants in the longitudinal Tucson Epidemiology Study of Obstructive Lung Disease who had at least one DL(CO) measurement during either of two surveys 8 yr apart (n = 543). Smoking status was determined at each examination (current, former, or never smoker). Quitters were defined as those currently smoking at the baseline DL(CO) examination (1982-1983) and self-reported as no longer smoking at the follow-up exam (1990-1991). The longitudinal DL(CO) data were analyzed using repeated measures analysis; because of missing observations this was done using a saturated random effects model. The results showed that males had higher levels of DL(CO) than females, current smokers had significantly lower levels of DL(CO) than never smokers, but there was no difference in their mean slopes over time. Smoking history, assessed using pack-years of smoking, was associated with reduced DL(CO) levels, independent of whether current or ex-smokers. Males and females demonstrated equivalent rates of decline in DL(CO) that accelerated with increasing age, and mean DL(CO) declines were associated with declines in FEV(1) between surveys.

Risk factors associated with complaints of insomnia in a general adult population. Influence of previous complaints of insomnia.

BACKGROUND: Insomnia is a common complaint both in the general population and also in physician's offices. However, risk factors for the development of insomnia complaints have not been completely identified. METHODS: To identify population characteristics associated with increased prevalence of insomnia complaints, we surveyed a large general adult population in 1984 through 1985. We evaluated the relationship among current complaints of initiating and maintaining sleep and obesity, snoring, concomitant health problems, socioeconomic status, and documented complaints of difficulty with insomnia 10 to 12 years previously. RESULTS: The strongest risk factor for complaints of initiating and maintaining sleep was previous complaints of insomnia (odds ratio, 3.5). In addition, female gender (odds ratio, 1.5), advancing age (odds ratio, 1.3), snoring (odds ratio, 1.3), and multiple types of concomitant health problems (odds ratios, 1.1 to 1.7) were all risk factors associated with an increased rate of complaints of initiating and maintaining sleep. CONCLUSION: Complaints of insomnia tend to be a persistent or recurrent problem over long periods of time. Female gender, advancing age, and concomitant health problems also are important risk factors.

Expiratory computed tomography for assessment of suspected pulmonary emphysema.

Results of computed tomography of the lung performed at two levels in upper lung zones at full inspiration and full expiration were compared with results of tests of ventilatory function, lung mechanics, and single breath carbon monoxide diffusing capacity in 64 subjects, many of whom had some form of airflow obstruction. From the CT scans, the mean percentage of pixels in the range -900 to -1,024 Hounsfield units, or pixel index, was determined for each subject. The highest correlations of pixel index with physiologic variables consistent with a diagnosis of emphysema were observed for CT taken at full expiration. In some subjects, the inspiratory CT would give a "false positive" for emphysema when the hyperaeration observed at inspiration was not observed at expiration. We believe that the CT scan taken at full expiration can effectively reveal the abnormal permanent enlargement of airspaces which defines emphysema and provides a noninvasive method of assessing lung morphology in the living human subject.

A longitudinal study of respiratory symptoms in a community population sample. Correlations with smoking, allergen skin-test reactivity, and serum IgE.

Chronic cough and/or phlegm, wheeze in the absence of colds, and rhinitis attributed to allergies are three of the most common respiratory symptoms encountered in community populations. In this study, we have determined the prevalence of these complaints in a random population sample (n = 1,109) using standardized questionnaires at two points in time, eight years apart. Cross-sectional prevalence and changes in symptom occurrence have been correlated with smoking status, allergen skin test reactivity, and total serum IgE levels. Our objective was to determine the individual and combined influence of these three variables on symptom prevalence. Initially, 19.2 percent of the population admitted to wheeze, 17.9 percent to cough, and 44.1 percent to allergic rhinitis. Cough and wheeze prevalence changed little over the eight-year period, while rhinitis increased 11 percent by the second survey. The occurrence of chronic cough was strongly correlated with smoking, and was not further influenced by either allergen skin reactivity or IgE level. Conversely, rhinitis prevalence was related to skin test reactivity with no additional association with smoking or IgE level. The occurrence of wheeze in the absence of colds was associated with both smoking and allergen skin reactivity. Among smokers, the prevalence was over 30 percent and was similar in both skin test positive (STP) and skin test negative (STN) individuals. However, on both surveys, STP ex-smokers and nonsmokers had significantly more wheeze than those who were STN. While the prevalence of wheeze in STN nonsmokers was low (6.8 percent), an IgE-wheeze relationship was also suggested on the second survey. In addition to these cross-sectional symptom relationships, changes in either smoking status or allergen skin reactivity during the study period were associated with changes in the prevalence of each symptom.

Single breath carbon monoxide transfer factor in different forms of chronic airflow obstruction in a general population sample.

The single breath transfer factor for carbon monoxide (TLCO), TLCO/alveolar volume (VA), and standard spirometric indices were measured in a survey of the randomly selected population sample of 1174 subjects enrolled in the Tucson epidemiological study of airways obstructive disease. Subjects were subdivided according to whether the FEV1/FVC ratio was under 65%, 65-75%, or over 75%. The influence of smoking on TLCO was accounted for by expressing TLCO as a percentage of the expected value-that is, of the value expected from the reported cigarette consumption. The 63 subjects who gave a history of physician confirmed asthma in reply to a questionnaire tended to have high values for TLCO, even when FEV1/FVC was reduced. In the absence of a given diagnosis of asthma, however, TLCO and TLCO/VA were reduced when the FEV1/FVC ratio was reduced, whether or not a clinical diagnosis of emphysema had been reported. This suggests that these subjects may have undiagnosed emphysema. This cross sectional analysis of our survey data suggests that subjects in our sample with spirometric evidence of chronic airflow obstruction have different forms of disease, characterised by different physiological features, in addition to the different risk factors and clinical courses reported earlier.

The effects of cigarette smoking and smoking cessation on the carbon monoxide diffusing capacity of the lung in asymptomatic subjects.

The single-breath carbon monoxide diffusing capacity (DL) was measured together with standard spirometry as part of a survey of a randomly selected community population sample. Based on answers to a self-administered questionnaire, subjects free of respiratory symptoms or disease were identified. Data from subjects who had never regularly smoked cigarettes had been used to derive reference equations for the test variables, and data from the remaining subjects who had smoked were examined to determine the effect of smoking and smoking cessation on the DL. From this cross-sectional analysis, it is apparent that cigarette smoking is associated with a decrease in DL that occurs very soon after beginning the cigarette habit. There is an irreversible decrease in DL with cumulative cigarette consumption, but also a reversible phenomenon that leads to rapid improvement in DL on smoking cessation.

Subclinical effects of cigarette smoking. A five-year follow-up of physiologic comparisons of healthy middle-aged smokers and nonsmokers.

Measurements of ventilatory function, lung elastic recoil, diffusing capacity, and distribution of ventilation were obtained on healthy middle-aged cigarette smokers and nonsmokers on two occasions five years apart in order to assess the effects of smoking and the change which may occur over this five-year interval. Subjects were drawn from a randomly selected sample of the population of Tucson, AZ. Exactly the same protocol, methods, and equipment were employed in both studies. Although very few of these healthy subjects had abnormal function, there were significant differences in most indices of function between smokers and nonsmokers. However, we could discern no difference between smokers and nonsmokers in change in function over five years. It appears that, in smokers who remain free of serious respiratory trouble, there are subtle changes which accumulate over the years and which are too gradual to detect over a five-year interval.

Risk factors in a general population for snoring. Importance of cigarette smoking and obesity.

In order to study risk factors associated with snoring in a general adult population, 2,187 subjects in the Tucson Epidemiologic Study of Obstructive Airways Disease were surveyed to determine the prevalence of snoring. Major independent risk factors for snoring were male gender, age between 40 and 64 years, obesity, and current cigarette smoking. Furthermore, greater intensity of cigarette smoking also was associated with higher snoring prevalence rates. Snoring prevalence remained elevated in subjects who recently quit smoking, but declined in ex-smokers to the level of never smokers within four years of smoking cessation. The presence of cough or sputum production was associated with an increase in snoring prevalence especially in ex-smokers. Snoring prevalence was slightly increased in subjects who regularly used alcohol or medications as aids to sleep. We conclude that cigarette smoking, obesity, male gender, age over 40, and use of alcohol or sleep medications are important risk factors for snoring. We propose that the effect of smoking may be related to the production of upper airway inflammation and edema by cigarette smoke, and that smoking cessation may eventually reduce snoring risk.

Respiratory effects of non-tobacco cigarettes.

Data from the Tucson epidemiological study of airways obstructive disease on smoking of non-tobacco cigarettes such as marijuana were analysed to determine the effect of such smoking on respiratory symptoms and pulmonary function. Among adults aged under 40, 14% had smoked non-tobacco cigarettes at some time and 9% were current users. The prevalence of respiratory symptoms was increased in smokers of non-tobacco cigarettes. After tobacco smoking had been controlled for men who smoked non-tobacco cigarettes showed significant decreases in expiratory flow rates at low lung volumes and in the ratio of the forced expiratory volume in one second to the vital capacity. This effect on pulmonary function in male non-tobacco cigarette smokers was greater than the effect of tobacco cigarette smoking. These data suggest that non-tobacco cigarette smoking may be an important risk factor in young adults with respiratory symptoms or evidence of airways obstruction.

Physiologic characteristics of subjects exhibiting accelerated deterioration of ventilatory function.

From a randomly selected community population sample followed with sequential surveys since 1972, 13 subjects who exhibited a mean annual decline in FEV1 greater than 60 ml/yr were drawn for detailed studies of lung function. These subjects had developed clinically significant airway obstruction during this period of follow-up. Clinical evaluation was not successful in characterizing the nature of the disorder. None of the subjects had alpha-1-antitrypsin deficiency. In a small proportion of subjects, elevated total serum immunoglobulin E may have played a role in the obstructive airway disorder. Some subjects exhibited loss of lung elastic recoil and diminished carbon monoxide diffusing capacity suggestive of developing emphysema. Others appeared to have intrinsic airway disease involving large and/or small airways, which may be fixed in some and responsive to bronchodilator in others. Thus, neither the site nor the nature of the disorder inferred from results of physiologic tests was uniform, illustrating the heterogeneous nature of chronic obstructive lung disease.

The single-breath carbon monoxide diffusing capacity. Reference equations derived from a healthy nonsmoking population and effects of hematocrit.

Measurements of the single-breath carbon monoxide diffusing capacity (DL) were obtained on a randomly selected sample representative of the white non-Mexican-American population of Tucson, Arizona. Methods of measurement followed the guidelines set forth in the ATS-sponsored Epidemiology Standardization Project. There were 228 healthy nonsmokers who had duplicate tests that met the criteria for being acceptable. On the basis of data from these subjects, reference equations were derived for DL, alveolar volume (VA), and DL/VA. The data demonstrate the effects of growth and development, height, and age on these variables. Because a significant proportion of women, but not of men, had low hematocrit values, an effect of hematocrit on DL and DL/VA could be demonstrated only in females in this population sample.

Assessment of air vs helium-oxygen flow-volume curves as an epidemiologic screening test.

Air and helium-oxygen maximum expiratory flow-volume curves were employed in an epidemiologic field study to assess the utility of density dependence as a screening test. Of 1,584 subjects tested, only 54.1 percent were able to perform the test with vital capacities for the two gases that agreed to within 5 percent. Subjects unable to perform the test properly tended to be older, with a greater prevalence of ventilatory function abnormalities and respiratory problems, than those who could perform the test. There was poor concordance between density dependence, or lack thereof, and standard ventilatory function measurements or evidence of respiratory disease. Under field survey conditions, the test of density dependence did not appear to be a useful screening tool.

Subclinical effects of smoking. Physiologic comparison of healthy middle-aged smokers and nonsmokers and interrelationships of lung function measurements.

Measurements of ventilatory function, distribution of ventilation, diffusing capacity, and lung mechanics were made on healthy middle-aged smokers and nonsmokers drawn from a randomly selected population in order to assess the effects of cigarette smoking and the interrelationships of the several indices of lung function. Although very few subjects had abnormal function, there were significant differences in most indices of function between smokers and nonsmokers. For the total group studied, there were significant correlations between various indices of function. A significant proportion of the variance in diffusing capacity and in diffusing capacity per liter of lung volume can be accounted for by an index of lung recoil which may, in turn, be related to size of terminal air spaces.

Evaluation of lung elastic recoil by exponential curve analysis.

Static deflation pressure-volume curves for the lungs of 104 subjects were satisfactorily fitted to an exponential function, V = Vmax - Ae-kP (where Vmax is volume V extrapolated to infinite transpulmonary pressure P, and A and k are constants). Subjects included 48 who met rigorous criteria defining normal, 35 were PiM phenotype for alpha-1-antitrypsin deficiency and 21 were PiMZ phenotype. The shape constant k was significantly related to age, whereas an index of curve position was not. Values for k corresponded closely to the data of other investigators suggesting that it was independent of size and insensitive to differences in experimental technique. Elevated values of k, indicative of emphysema, were no more prevalent among PiMZ subjects than among subjects with no alpha-1-anti-trypsin deficiency. The natural logarithm (1n) of k, rather than k itself, appears to provide a useful, normally distributed, expression of lung distensibility.