Biomedical subjects

M R Segal

Publications and source records attributed to M R Segal.

At least 19 recordsLinked to original sources

PubMed1992

An annotated bibliography of methods for analysing correlated categorical data.

This paper provides an annotated bibliography of over 100 articles concerning methods for analysing correlated categorical response data. Most of the papers listed here concern categorical regression models and estimation, with particular emphasis on binary responses. The papers are classified by several characteristics which group them according to common themes. The bibliography serves as a reference of methods for analysts of correlated categorical data, as well as for persons interested in methodologic work in this active area of statistical research.

Clinical Trials as Topic↗

PubMed1992

The relationship of nasal disorders to lower respiratory tract symptoms and illness in a random sample of children.

We examined the relationship of nasal disorders, defined as frequent colds and sinus trouble, to lower respiratory tract symptoms in a random population of 718 children aged 4 to 11 years in East Boston, Massachusetts. Frequent colds were significantly associated with maternal smoking (odds ratio (OR) = 3.00; 95% confidence interval (CI) = 1.97, 4.58), and so was sinus trouble (OR = 4.73; 95% CI = 1.78, 12.51). After adjustment for maternal smoking, age and sex, frequent colds (OR = 2.88; 95% CI = 1.87, 4.42) and sinus trouble (OR = 4.95, 95% CI = 1.83, 13.39) remained significant predictors of lower respiratory tract symptoms in separate logistic regressions. If one restricted the cohort to the 513 children who also had personal smoking information and adjusted for this variable as well, the results for colds were unchanged (OR = 2.94; 95% CI = 1.78, 4.84) but the results for sinus trouble were now not statistically significant (OR = 2.30, 95% CI = 0.67, 7.94). We conclude that nasal disorders are associated with lower respiratory tract symptoms in children.

Child↗

PubMed1992

Effects of asthma on pulmonary function in children. A longitudinal population-based study.

Data from a longitudinal study of childhood factors influencing the development of chronic obstructive lung disease were used to assess the effects of asthma on lung function development in male and female children. A population-based cohort of 602 white children, initially aged 5 to 9 yr, was observed prospectively for 13 yr. Spirometry was performed and a standardized respiratory and illness questionnaire was administered by trained interviewers on a yearly basis. Forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and forced expiratory flow between 25 and 75% of vital capacity (FEF25-75) were used as measures of lung function. The total number of children reporting asthma over the course of the study was 67. Male asthmatic subjects (n = 42) had larger average percentage of predicted FVC than nonasthmatic males (n = 277). Female asthmatic subjects (n = 23) had a lower average percentage of predicted FEV1 than nonasthmatic females (n = 260). In a multivariate analysis of the individual lung function measures, adjusting for previous level of pulmonary function, age, height, change in height, and personal and maternal smoking, males reporting active asthma had a significantly larger FVC than males with no history of asthma. In contrast, females with active asthma had a significantly smaller FEV1 than females with no history of asthma. Both males and females with active asthma had decreased FEF25-75. From our analysis, we would predict that a female who develops asthma at age 7 would experience a 5% reduction in FEV1 by age 10 and a 7% deficit by age 15.(ABSTRACT TRUNCATED AT 250 WORDS)

Asthma↗

PubMed1992

The effect of maternal smoking during pregnancy on early infant lung function.

We studied the effect of prenatal maternal cigarette smoking on the pulmonary function (PF) of 80 healthy infants tested shortly after birth (mean, 4.2 +/- 1.9 wk). Mothers' prenatal smoking was measured by: (1) questionnaire reports at each prenatal visit of the number of cigarettes smoked per day, and (2) urine cotinine concentrations (corrected for creatinine) obtained at each visit. Infant PF was assessed by partial expiratory flow-volume curves and helium-dilution measurement of FRC. Forced expiratory flow rates were significantly lower in infants born to smoking mothers, both when unadjusted and after controlling for infant size, age, sex, and passive exposure to environmental tobacco smoke (ETS) between birth and the time of PF testing. Flow at functional residual capacity (VFRC) in infants born to smoking mothers was lower than that found in infants whose mothers did not smoke during pregnancy (74.3 +/- 15.9 versus 150.4 +/- 8.9 ml/s; p = 0.0007). Differences remained significant when flow was corrected for lung size (VFRC/FRC: 0.87 +/- 0.26 versus 1.77 +/- 0.12 s-1; p = 0.013). No differences in pulmonary function were evident among infants exposed and unexposed to ETS in the home after stratifying by prenatal exposure status. We conclude that maternal smoking during pregnancy is associated with significant reductions in forced expiratory flow rates in young infants. The results suggest that maternal smoking during pregnancy may impair in utero airway development and/or alter lung elastic properties. We speculate that these effects of maternal prenatal smoking on early levels of forced expiratory flow may be an important factor predisposing infants to the occurrence of wheezing illness later in childhood.

Adult↗

PubMed1992

Living arrangements and survival among middle-aged and older adults in the NHANES I epidemiologic follow-up study.

BACKGROUND: There is concern about but little information on how living alone affects the health and survival of older adults. METHODS: We examined the association between living arrangements (living alone, with a spouse, or with someone other than a spouse) and survival among 7651 adults, aged 45 to 74 years in the National Health and Nutrition Examination Survey (NHANES I) (1971-1975) and traced at the NHANES I Follow-up Study (1982-1984), to see whether certain sociodemographic factors (race, education, income, and employment), health behaviors (alcohol, smoking, physical activity, and obesity), or chronic medical conditions were influential in the association. RESULTS: We found a stronger association of living arrangements with survival for men than for women, and for middle-aged men than for older men. For men, those living alone and those living with someone other than a spouse were equally disadvantaged in terms of survival. Income, race, employment, and physical activity influenced the association of living arrangements and survival, but their impact varied by age, gender, and living arrangement. CONCLUSION: Living arrangements had a weak impact on survival among men, but had no effect among women.

Age Factors↗

PubMed1992

Correlates of knee pain among US adults with and without radiographic knee osteoarthritis.

We examined the associations of sociodemographic variables, health behaviors, health status and psychological well being with radiographic knee osteoarthritis (OA) and self-reported knee pain for 4056 US adults aged 45-74 years. Among persons with or without knee OA known correlates of radiographic knee OA (age, sex, race, obesity) were generally not associated with knee pain. Radiographic severity, psychological well being and health status were associated with knee pain, both among persons with and without radiographic knee OA, suggesting that nonradiographic correlates of self-reported knee pain are independent of whether a person has radiographic knee OA.

Age Factors↗

PubMed1991

The influence of age and level of pulmonary function on nonspecific airway responsiveness. The Normative Aging Study.

The relationship of age and prechallenge FEV1 to methacholine airway responsiveness was examined among 914 male participants of the Normative Aging Study (age range 41 to 86 yr). Methacholine airway responsiveness was analyzed as both a continuous (dose-response slope) and categorical (PD20 FEV1 greater than 8.6 mumol; PD20 FEV1 less than or equal to 8.6 mumol) variable. Methacholine responsiveness, as assessed by dose-response slope, displayed a significant inverse relationship to the prechallenge level of FEV1 (p less than 0.001). The dose-response slope was directly related to age among former smokers (p = 0.003) but not among current and never smokers. Using a categorical variable rather than the dose-response slope to characterize responder status yielded very similar results. A logistic regression model of the data predicts an approximately threefold greater odds of a positive methacholine challenge test in association with a 500 ml lower FEV1. The model predicts that among former smokers a 20-yr increase in age is associated with an approximately fivefold increase in the odds of a positive methacholine challenge test. This analysis suggests that nonspecific airway responsiveness increases with advancing age among former smokers even after adjustment for prechallenge level of FEV1.

Adult↗

PubMed1991

Temporal trends in chronic obstructive lung disease case fatality in hospitalized US veterans: 1970-1987.

Vital statistics data have suggested that age-adjusted mortality from chronic obstructive lung diseases (CLD) is increasing. The present investigation has used the US Veterans Administration (VA) hospital computer database to determine whether trends in CLD case fatality follow trends in CLD population mortality. Data for male patients discharged from 172 VA hospitals from 1970 through 1987 were utilized. Patients were included if they had a CLD as a first-listed hospital discharge diagnosis, did not have any of a number of smoking-related cardiovascular or malignant diseases, and were born in the years 1900 through 1939. While crude case fatality for all CLD increased from 5.2 percent in 1970 to 7.4 percent in 1987, age-adjusted case fatality decreased from a peak of 8.5 percent in 1971 to 5.8 percent (95 percent confidence interval, 5.4 to 6.61 percent) in 1987. This trend was seen for all CLD diagnoses, including asthma. Age-specific case fatality decreased for each successive 5-year birth cohort, and age at death remained relatively constant over the last 14 years of the study. The declining case fatality could not be explained by changes in the ICD coding rubrics. The extent to which case fatality has been declining due to improved treatment and/or cohort-related changes in tobacco smoke exposure could not be determined definitively from the data.

Age Factors↗

PubMed1990

Body fat distribution, blood pressure, and hypertension. A prospective cohort study of men in the normative aging study.

The relation between the abdominal accumulation of body fat, blood pressure, and hypertension was assessed prospectively among 1972 male participants in the Veterans Administration Normative Aging Study. Body mass index (BMI = weight [kg]/height [m]2) and the ratio of abdominal circumference to hip breadth (AC/HB), measured at regular exams, were used as indices of total adiposity and body fat distribution, respectively. Considering blood pressure as a continuous outcome variable (in models that allowed for intraclass correlation), the AC/HB ratio was significantly positively associated with both diastolic and systolic blood pressure (P < 0.001), adjusting for age and BMI. Blood pressure was dichotomized and hypertension risk was assessed using the proportional hazards model, adjusting for age and BMI. Seven hundred cases of hypertension were recorded by study physicians during 35,496 person-years of follow-up. The risk of hypertension increased approximately three-fold (95% confidence interval, 1.7 to 5.2) with a change of one unit in the AC/HB ratio. These estimates were little changed when the effects of smoking and alcohol intake were considered. Thus, the abdominal accumulation of body fat, apart from overall level of adiposity, was associated with both increased blood pressure and an increased risk of hypertension.

Adult↗

PubMed1990

Patterns of weight change and their relation to diet in a cohort of healthy women.

Patterns of weight change for 31,940 non-smoking women aged 30-55 y in 1976 were examined for 8 y of follow-up. Each woman reported her weight every 2 y on questionnaires, and diet was assessed in 1980 with a semiquantitative food frequency questionnaire. Self-reported weight was highly correlated over time, decreasing from r = 0.95 over 2 y to r = 0.89 over 8 y. Weight gain was inversely related to age (r = -0.06). Weight change in a given 2-y interval was inversely related to change in weight over the subsequent 2 y (r = -0.30). Age, relative weight, and prior weight change were stronger predictors of recent weight change than were intake patterns of specific nutrients. Recent prior weight change was the strongest predictor of subsequent weight change. In a population of free-living women, prior weight loss and younger age are far stronger predictors of subsequent weight gain than are the qualitative aspects of diet.

Adult↗

PubMed1990

The relationship of nonspecific airway responsiveness and atopy to the rate of decline of lung function. The Normative Aging Study.

Nonspecific airway hyperresponsiveness and atopy have been postulated to be risk factors that predispose individuals to the development of chronic obstructive pulmonary disease. The purpose of the present study was to examine the relationship of methacholine airway responsiveness and markers of atopy to rate of decline in lung function among 790 men, age 40 to 79 yr, followed in the Normative Aging Study. Airway responsiveness was assessed at the end of follow-up, which ranged from 14 to 24 yr. Multiple linear regression analysis indicated that greater methacholine airway responsiveness was associated with more rapid annual FEV1 decline. Stratified analysis suggested that this association was stronger among skin test-negative, current smokers. No significant relationship was found between serum IgE level and annual FEV1 decline. A weak but statistically significant correlation between eosinophil count and mean annual FEV1 decline was noted among skin test-negative individuals (r = -0.08; p = 0.03). Results from the present study do not show a clear association between atopy and decline in FEV1. These data, however, do indicate an independent association between heightened methacholine responsiveness on decline in FEV1 in adult males.

Adult↗

PubMed1990

Pulmonary function measures in healthy infants. Variability and size correction.

We conducted 151 tests of pulmonary function (PF) on 72 healthy infants younger than 2 yr of age using partial expiratory flow volume (PEFV) maneuvers and helium dilution determination of FRC. After tests were grouped into four strata based on postconception (PC) age, variability and sex differences in level of PF were examined. No significant sex differences were found for any PF measure in any age stratum, even when somatic size was controlled by length correction. Force expiratory flow measures, however, tended to be greater in girls than in boys in the youngest infants. Flow measures demonstrated greater between-subject variability than did volumes, and variability was greatest in the youngest infants. Within-subject variability also was more pronounced for flow measures, particularly in infants younger than 50 PC wk of age. Across the age range of infants studied, all PF measures were related linearly to somatic size as measured by either length, weight, or chest circumference. Length offered the best individual size correction of the three size parameters studied. Linear regression of PF parameters versus length demonstrated FRC to increase at 5.39 ml/cm over this age range, whereas flow at FRC increased by 9.67 ml/s/cm. We conclude that the variability of infant PF measures is greatest in early infancy, that measures of forced expiratory flow are more variable than volume measures, and that sex differences in infant PF do not appear significant. Length is related linearly to PF measures and offers reasonable size correction for healthy infants younger than 18 months of age.

Age Factors↗

PubMed1990

The relationship of body fat distribution to blood pressure in normotensive men: the normative aging study.

Body fat distribution may be a more specific marker than obesity for risk of cardiovascular disease and diabetes. The relationship between body fat distribution and sitting systolic and diastolic blood pressure was examined in a cross-sectional analysis of 1936 normotensive men aged 21 to 80 years. In this analysis body fat distribution was represented by the ratio of abdomen circumference to hip breadth (denoted as WHbR). Pearson product-moment correlations adjusted for age revealed a positive correlation between WHbR and both systolic and diastolic blood pressure (r = 0.13 and r = 0.14, respectively). In a multiple linear regression model controlling for age, smoking status and body mass index (BMI), WHbR was associated with systolic blood pressure [regression coefficient (standard error) = 3.58 (1.8), P = 0.048)], but had much less of an association with diastolic blood pressure [regression coefficient (standard error) = 1.90 (1.3), P = 0.141]. Further adjustment for alcohol intake decreased the association between WHbR and systolic blood pressure [regression coefficient (standard error) = 2.90 (1.81), P = 0.110]. Body fat distribution, as represented by WHbR was associated with level of systolic blood pressure independently of overall level of obesity (BMI) in normotensive men; adjustment for alcohol intake attenuated the relationship. These data suggest that dietary factors, notably alcohol intake, may influence the effect of body fat distribution on blood pressure.

Adipose Tissue↗

PubMed1989

A comparison of estimated proportional hazards models and regression trees.

We present examples of the usage of regression trees for censored response via two real world datasets, one a rheumatoid arthritis survival study and the other a hip replacement study, and draw comparisons with the results of Cox proportional hazards modelling. The two methods pursue different goals. Motivation of the tree techniques is the desire to extract meaningful prognostic groups while the proportional hazards model enables assessment of the impact of risk factors. The methods are thus complementary. For the arthritis study the two techniques corroborate one another, although the flavour of the conclusions derived differ. For the hip replacement study, however, the regression tree approach reveals structure that would not emerge from a routine proportional hazards analysis. We also discuss the treatment of data analytic issues such as the handling of missing values and influence in the presence of non-uniform censoring.

Aged↗

PubMed1989

Comparison of questionnaire and diary methods in acute childhood respiratory illness surveillance.

We compared two prospective survey methods, an interviewer-administered questionnaire and a daily diary, used concurrently to record acute respiratory illness experience over a 2-yr period in 422 children 5 to 11 yr of age from East Boston, Massachusetts. Respondents contributed more months of data with the questionnaire than with the diary method. Respiratory symptom and illness rates, as determined for the first year by each of the methods, were compared for 277 children who had less than 4 months of missing data. Respondents from families with more children tended to report a lower total respiratory illness rate by the diary than by the questionnaire method (p = 0.006). Although upper respiratory illness rates did not differ by method, lower respiratory illnesses were reported more frequently (p = 0.0001) by questionnaire than by diary. In the group of 49 children who were identified as having had greater than one lower respiratory illness, 25% of the illnesses reported as having been lower respiratory by questionnaire were reported as having been another form of respiratory illness by diary. For this group the ratio of 3:1 of boys to girls for the diary as compared with 1.5:1 for the questionnaire suggests the presence of reporting bias and no comparability of methods. Standardization of an acute respiratory illness questionnaire would provide greater opportunity than use of diaries for synthesis of prospective data from different epidemiologic studies.

Acute Disease↗

PubMed1989

The relationship between longitudinal change in pulmonary function and nonspecific airway responsiveness in children and young adults.

The relationship between airway hyperresponsiveness and longitudinal change in lung function was assessed in a population-based sample of 184 children and young adults observed over a maximum span of 12 yr. Pulmonary function was assessed annually with spirometry, and health and household information was obtained with standardized questionnaires. Nonspecific airway responsiveness to eucapneic hyperventilation with subfreezing air was measured on at least two occasions between the sixth and twelfth annual surveys. At any given survey, a significant bronchoconstrictor response was defined as [( prechallenge FEV1-postchallenge FEV1]/pre-FEV1) greater than or equal to 0.13, a value that identified 10% of the population. Subjects were classified as "never", "always", or "inconsistent" responders according to the consistency of responsiveness determined in different surveys. Subjects were classified further as "labile" if their maximal survey-to-survey difference in delta FEV1/FEV1 was greater than or equal to 0.18, and as "nonlabile" otherwise. A Markov-type autoregressive model that adjusts for previous pulmonary function level, sex, growth variables, and smoking exposures was used to model growth of FEV1, FEF25-75, and FVC. Overall, 135 (73%) of subjects never responded to the cold air challenge, six (3%) always responded, and 43 (24%) responded on one but not all occasions. Levels and rates of increase in level of FEF25-75 were significantly lower in the inconsistent and always responders. In contrast, levels of FVC were greatest and increased most in the always responders. In labile subjects, both FEF25-75 and FEV1 growth rates were reduced. These effects persisted when asthmatics were excluded from the analyses.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1989

Firefighting acutely increases airway responsiveness.

The acute effects of the products of combustion and pyrolysis on airway responsiveness among firefighters are poorly documented. To study this relationship, spirometry and methacholine challenge testing (MCT) were performed on 18 active Seattle firefighters before and 5 to 24 h after firefighting. Body plethysmography was used to measure changes in specific airway conductance (SGaw), and results of MCT were analyzed using PD35-SGaw, the cumulative dose causing a 35% decrease in SGaw. Subjects who did not react by the end of the protocol were assigned a value of 640 inhalational units, the largest cumulative dose. Fire exposure was defined as the total time (hours) spent without a self-contained breathing apparatus at the firesite and was categorized as mild (less than 1 h, n = 7), moderate (1 to 2 h, n = 5), or severe (greater than 2 h, n = 6). Mean age of the 18 firefighters was 36.7 +/- 6.7 yr (range, 25 to 51), with a mean of 9.1 +/- 7.9 active years in the trade (range, zero to 22). None was known to be asthmatic. After firefighting, FEV1 % predicted (%pred) and FEF25-75 %pred significantly decreased by means of 3.4 +/- 1.1% and 5.6 +/- 2.6%, respectively. The mean decline in PD35-SGaw after firefighting was 184.5 +/- 53.2 units (p = 0.003). This observed decline in PD35-SGaw could not be explained by decrements in prechallenge SGaw, FEV1, or FVC.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1989

Alcohol consumption and chronic obstructive pulmonary disease.

This study examined the relationship between lifetime alcohol consumption and respiratory symptoms in 195 subjects (including 111 alcoholics) and FEV1 level in 165 subjects (including 91 alcoholics). After adjustment for age and cigarette smoking status, using multiple logistic regression, lifetime alcohol consumption was a significant predictor of chronic cough and chronic phlegm, but not of any wheeze or persistent wheeze. Multiple linear regression analysis indicated that lifetime alcohol consumption was also a predictor of lower levels of FEV1 in a model that included age, pack-years of cigarette smoking, and an interaction between alcohol consumption and pack-years. The interaction between smoking and alcohol consumption was in a direction opposite to the independent effects of alcohol and smoking, suggesting a protective effect of alcohol with heavier amounts of smoking. Additional study is needed to further assess the relationship between respiratory symptoms and alcohol consumption, and between pulmonary function and alcohol consumption.

Adult↗