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W D Flanders

Publications and source records attributed to W D Flanders.

At least 55 records · Page 3Linked to original sources
PubMed1996

Heat-related deaths during the July 1995 heat wave in Chicago.

BACKGROUND: During a record-setting heat wave in Chicago in July 1995, there were at least 700 excess deaths, most of which were classified as heat-related. We sought to determine who was at greatest risk for heat-related death. METHODS: We conducted a case-control study in Chicago to identify risk factors associated with heat-related death and death from cardiovascular causes from July 14 through July 17, 1995. Beginning on July 21, we interviewed 339 relatives, neighbors, or friends of those who died and 339 controls matched to the case subjects according to neighborhood and age. RESULTS: The risk of heat-related death was increased for people with known medical problems who were confined to bed (odds ratio as compared with those who were not confined to bed, 5.5) or who were unable to care for themselves (odds ratio, 4.1). Also at increased risk were those who did not leave home each day (odds ratio, 6.7), who lived alone (odds ratio, 2.3), or who lived on the top floor of a building (odds ratio, 4.7). Having social contacts such as group activities or friends in the area was protective. In a multivariate analysis, the strongest risk factors for heat-related death were being confined to bed (odds ratio, 8.2) and living alone (odds ratio, 2.3); the risk of death was reduced for people with working air conditioners (odds ratio, 0.3) and those with access to transportation (odds ratio, 0.3). Deaths classified as due to cardiovascular causes had risk factors similar to those for heat-related death. CONCLUSIONS: In this study of the 1995 Chicago heat wave, those at greatest risk of dying from the heat were people with medical illnesses who were socially isolated and did not have access to air conditioning. In future heat emergencies, interventions directed to such persons should reduce deaths related to the heat.

Aged↗
PubMed1996

Reliability of alcohol intake as recalled from 10 years in the past.

The authors assessed the reliability of alcohol intake as recalled from 10 years in the past in a cohort of 2,907 US adults. Participants reported their drinking habits in the First National Health and Nutrition Examination Survey interview during 1971-1975. During a follow-up interview in 1982-1984, they were asked to recall their drinking habits 10 years earlier and to report their current habits. In general, the correlation for recalled alcohol intake versus reported intake at baseline was good (r = 0.7). For all subgroups stratified by race, sex, education, smoking status, and disease status, the age-adjusted correlations for recalled alcohol intake versus baseline intake were equal to or higher than those for current alcohol intake versus baseline intake. The reliability of recall of alcohol intake in the past differs among subgroups with different age and education levels. Recalled alcohol intake was also highly correlated with current alcohol intake; in particular, current heavier drinkers tended to underestimate their previous amount of drinking, an effect that was independent of other factors. These data suggest that although recalled alcohol intake is a better predictor of past intake than are reports of current intake, current drinking habits may be an important influencing factor in the estimation of alcohol intake as recalled from the distant past.

Adult↗
PubMed1996

Bias in case-control studies of screening effectiveness.

Screening programs, such as annual mammography, are undertaken to reduce mortality and/or morbidity from chronic diseases such as cancer. Matched case-control studies have been used to assess the effectiveness of screening programs because of their relative simplicity and low cost. In such studies, the exposure history for controls consists of the number of screening examinations received prior to the date of diagnosis of the matched case. The authors know of no methodological evaluations that demonstrate the validity of such case-control studies. To examine the possible existence of bias due to design rules, the authors developed a simple deterministic model, which is used to calculate expected screening and disease patterns in a cohort. Cases and matched controls are selected from the cohort, and their screening histories are used to calculate an odds ratio, as is commonly done in practice. Results utilizing this simple model suggest that systematic inclusion of the examination from which diagnosis is made, which is the approach typically used in practice, leads to a positive bias (odds ratio > 1) in the absence of any real effect. Systematic exclusion of this examination appears to lead to a negative bias (odds ratio < 1). Although this simple approach has several limitations, the results suggest that a commonly used method of conducting case-control studies may yield biased odds ratios. Possible methods to reduce this bias may exist, such as defining exposure intervals differently.

Bias↗
PubMed1996

Genetic epidemiologic methods to screen for matrilineal inheritance in mitochondrial disorders.

We propose a method to screen for the matrilineal inheritance in mitochondrial disorders by comparing the risk of disease in a person whose mother is affected or whose maternal grandmother or aunt or uncle is affected to the risk of disease in a person whose father is affected or whose paternal grandmother or aunt or uncle is affected using a modification of the reconstructed cohort design. Sampling of pedigrees is accomplished via probands and must not be influenced by family history. The cohort of the proband's offspring, and offspring of the proband's siblings, can be analyzed using survival analysis. Cox proportional hazards model, Bonney's [(1986) Biometrics 42:611-625] model, and Liang's [(1991) Genet Epidemiol 8:329-338] model. Mitochondrial transmission can be distinguished from X-linked transmission by examining sex-specific patterns of disease expression in matrilineally transmitted diseases. To illustrate our epidemiologic method, we apply our screening method to pedigrees of two disorders which have been proposed to have a mitochondrial DNA component to their inheritance.

Bipolar Disorder↗
PubMed1996

Cigarette smoking and leukocyte subpopulations in men.

Because of previously reported associations among the total leukocyte count, cigarette smoking, and risk of cardiovascular disease, we examined the relation of cigarette smoking to various leukocyte subpopulations among 3467 men aged 31 to 45 years. The median total leukocyte count was 36% higher (7840 vs. 5760 cells/mL) among current cigarette smokers than among men who had never smoked, and both stratification and regression analyses were used to examine independent associations with leukocyte subpopulations. At equivalent counts of other subpopulations, CD4+ lymphocytes and neutrophils were the cell types most strongly associated with cigarette smoking; each standard deviation change in counts of these subpopulations increased the odds of current (vs. never) smoking by approximately threefold. Furthermore, whereas 15% of the 238 men with relatively low (< 25 percentile) counts of both neutrophils and CD4+ lymphocytes were cigarette smokers, 96% of the 249 men with relatively high counts of both subpopulations were current smokers. Counts of T lymphocytes also tended to be higher among the 32 men with self-reported ischemic heart disease than among other men. These results, along with previous reports of immunologically active T lymphocytes in atherosclerotic plaques, suggest that this subpopulation may be of particular interest in studies examining the relation of leukocytes to cardiovascular disease.

Adult↗
PubMed1996

Combat exposure and adult psychosocial adjustment among U.S. Army veterans serving in Vietnam, 1965-1971.

This study investigated the relationship between combat exposure and adult antisocial behavior in a sample of 2,490 male Army veterans of the Vietnam War who completed questionnaires about their psychological functioning. After adjustment for history of childhood behavior problems, posttraumatic stress disorder diagnosis, and demographic and military characteristics, it was found that veterans who experienced high and very high levels of combat were twice as likely to report adult antisocial behavior as veterans with no or low levels of combat and were also more likely to meet criteria for antisocial personality disorder. The results indicate that exposure to traumatic events during late adolescence or early adulthood is associated with multiple adult adjustment problems in vocational, interpersonal, and societal functioning. Treatment focusing on the effects of the trauma is likely to be necessary but not sufficient for improving affected veterans' behavior.

Adult↗
PubMed1996

Risk factors for self-reported uterine fibroids: a case-control study.

To identify risk factors for uterine fibroids, a case-control design used to analyze data from control subjects enrolled in the Cancer and Steroid Hormone Study. Case patients were 201 women who reported a history of uterine fibroids, and control subjects were 1503 women without fibroids, individually matched by age to case patients. Reporting of fibroids was more frequent among premenopausal women, women who had frequent Papanicolaou (Pap) smears, women who used oral contraceptives and had infrequent Pap smears, and women with higher education. Reporting of fibroids was less frequent among women with a lower body mass index who were current or long-time smokers.

Adult↗
PubMed1996

Advanced maternal age and the risk of Down syndrome characterized by the meiotic stage of chromosomal error: a population-based study.

The identification of DNA polymorphisms makes it possible to classify trisomy 21 according to the parental origin and stage (meiosis I [MI], meiosis II [MII], or postzygotic mitotic) of the chromosomal error. Studying the effect of parental age on these subgroups could shed light on parental exposures and their timing. From 1989 through 1993, 170 infants with trisomy 21 and 267 randomly selected control infants were ascertained in a population-based, case-control study in metropolitan Atlanta. Blood samples for genetic studies were obtained from case infants and their parents. Using logistic regression, we independently examined the association between maternal and paternal age and subgroups of trisomy 21 defined by parental origin and meiotic stage. The distribution of trisomy 21 by origin was 86% maternal (75% MI and 25% MII), 9% paternal (50% MI and 50% MII), and 5% mitotic. Compared with women <25 years of age, women > or = 40 years old had an odds ratio of 5.2 (95% confidence interval, 1.0-27.4) for maternal MI (MMI) errors and 51.4 (95% confidence interval, 2.3-999.0) for maternal MII (MMII) errors. Birth-prevalence rates for women > or = 40 years old were 4.2/1000 births for MMI errors and 1.9/1000 for MMII errors. These results support an association between advanced maternal age and both MMI and MMII errors. The association with MI does not pinpoint the timing of the error; however, the association with MII implies that there is at least one maternal-age related mechanism acting around the time of conception.

Adult↗
PubMed1996

A modified cluster-sampling method for post-disaster rapid assessment of needs.

The cluster-sampling method can be used to conduct rapid assessment of health and other needs in communities affected by natural disasters. It is modelled on WHO's Expanded Programme on Immunization method of estimating immunization coverage, but has been modified to provide (1) estimates of the population remaining in an area, and (2) estimates of the number of people in the post-disaster area with specific needs. This approach differs from that used previously in other disasters where rapid needs assessments only estimated the proportion of the population with specific needs. We propose a modified n x k survey design to estimate the remaining population, severity of damage, the proportion and number of people with specific needs, the number of damaged or destroyed and remaining housing units, and the changes in these estimates over a period of time as part of the survey.

Cluster Analysis↗
PubMed1996

Suicidal risk during controlled clinical investigations of fluvoxamine.

BACKGROUND: Suicide is a serious risk factor in major depressive disorder. Paradoxical emergence of suicidal ideation or behavior during antidepressant treatment has been reported in isolated cases. An evaluation was undertaken to assess the risk of suicidality during treatment with fluvoxamine, a serotonin selective reuptake inhibitor. METHOD: Meta-analyses were conducted on pooled data from double-blind, randomized, placebo-controlled, parallel-group clinical trials. The primary outcome measure was the suicide item of the Hamilton Rating Scale for Depression. Tests for emergence of substantial suicidal ideation and improvement or worsening in suicidal ideation were performed using the Mantel-Haenszel adjusted incidence difference. The Breslow-Day test was used to test for lack of homogeneity across trials. Secondary analysis, which consisted of Pearson's chi-square test, was used to confirm the Mantel-Haenszel result. RESULTS: In comparison to placebo, fluvoxamine was associated with significantly greater improvement in suicidal ideation (p = .01) and significantly less worsening of suicidal ideation (p < .01). No differences were found in the emergence of substantial suicidal ideation. CONCLUSION: These findings demonstrate that fluvoxamine is not associated with an increased risk of emergence of substantial suicidal thoughts among depressed patients. On the contrary, the results are suggestive of a protective effect of fluvoxamine upon the risk of suicidal ideation.

Adult↗
PubMed1995

Basic models for disease occurrence in epidemiology.

BACKGROUND: One of the epidemiologist's most basic tasks is estimation of disease occurrence. To perform this task, the epidemiologist frequently models variability in disease occurrence using one of three distributions--the binomial, the Poisson or the exponential distribution. Although epidemiologists often use them and their properties appear in standard texts, we know of no text or review that compares and contrasts epidemiological application of these distributions. METHODS: In this commentary, we discuss these three basic distributions. We note key assumptions as well as limitations, and compare results from analyses based on each distribution. RESULTS AND CONCLUSIONS: We illustrate that the three distributions, although superficially different, often lead to similar results. We argue that epidemiologists should often obtain similar results regardless of which distribution they use. We also point out that application of all three distributions can be inappropriate if assumptions of independence or homogeneity of risks fail to hold. Finally, we briefly review how these basic distributions can be used to justify use of other distributions, such as the Gaussian distribution, for studying disease-exposure associations.

Binomial Distribution↗
PubMed1995

Methodology to correct for differential misclassification.

Misclassification of exposure is a serious problem in epidemiology. Methods for addressing misclassification are available, but most are based on limiting assumptions such as availability of a "gold standard" measure of true exposure, or availability of two tests of exposure whose performance is nondifferential. In this paper, we discuss a method that allows the investigator to correct for differential misclassification in case-control studies. Our method only requires two potentially imperfect tests for measuring exposure. Importantly, the sensitivity and specificity of each test when applied to cases may differ from the sensitivity and specificity when applied to controls. The approach does require two subgroups of cases, such that each test's sensitivity and specificity is the same across these subgroups and requires analogous subgroups for controls. We exemplify our approach in several ways, using hypothetical data, using data from a case-control study of birth defects and service in Vietnam, and by a small Monte Carlo study. Finally, we discuss limitations of the method.

Bias↗
PubMed1995

Bias in using family history as a risk factor in case-control studies of disease.

In many case-control studies of common diseases, investigators use family history information to assess familial aggregation of the disease and the influence of genetic factors. Positive family history among first-degree relatives is often used as a risk factor, and its odds ratio is calculated. Although the limitations of this approach have been discussed, it is not clear how much impact such limitations could have on measuring familial aggregation. To assess this impact, we compare odds ratios derived from using a positive family history in case-control studies with measures of relative risk derived from comparing lifetime risks of disease among first-degree relatives of case subjects with those among first-degree relatives of control subjects. Positive family history is a function of the number of relatives, the background risk of disease, the age distribution of relatives, and the correlation in risk among relatives. It can be shown that even without case-control differences in the number or ages of relatives, positive family history tends to overestimate relative risk measures applied to individual relatives. This overestimation is accentuated with increasing frequency of the disease, with increasing number of relatives, and for diseases with earlier age at onset. It is further affected by even small case-control differences in family size and age distribution of relatives. As such, positive family history is not a stable indicator of familial aggregation across different case-control studies of the same disease.

Aged↗
PubMed1995

Half-life of polybrominated biphenyl in human sera.

Polybrominated biphenyl (PBB), a flame-retardant material, was introduced into the food chain in Michigan in 1973 due to a manufacturing and distribution mistake. Following public concern about the long-term health effects of PBB in humans, a cohort of PBB-exposed Michigan residents was assembled in 1975. We initiated this study to determine the half-life of PBB in human sera and to understand how continued body burden relates to the possible adverse health consequences of PBB exposure. To determine the half-life, eligible persons were selected from the cohort if they had at least two PBB measurements 1 year apart and had an initial level > or = 20 pbb. There were 163 persons who met the criteria with a median PBB level of 45.5 ppb. The estimated half-life is 10.8 years (95% CI, 9.2-14.7 years). The body burden of PBB in exposed persons will decrease only gradually over time. For persons with an initial level of 45.5 ppb of PBB, it will take more than 60 years for their PBB levels to fall below the current level of detection of 1 ppb.

Adult↗
PubMed1995

Excess mortality among cigarette smokers: changes in a 20-year interval.

OBJECTIVES: This study was undertaken to examine changes in smoking-specific death rates from the 1960s to the 1980s. METHODS: In two prospective studies, one from 1959 to 1965 and the other from 1982 to 1988, death rates from lung cancer, coronary heart disease, and other major smoking-related diseases were measured among more than 200,000 current smokers and 480,000 lifelong non-smokers in each study. RESULTS: From the first to the second study, lung cancer death rates (per 100,000) among current cigarette smokers increased from 26 to 155 in women and from 187 to 341 in men; the increase persisted after current daily cigarette consumption and years of smoking were controlled for. Rates among nonsmokers were stable. In contrast, coronary heart disease and stroke death rates decreased by more than 50% in both smokers and nonsmokers. The all-cause rate difference between smokers and nonsmokers doubled for women but was stable for men. CONCLUSIONS: Premature mortality (the difference in all-cause death rates between smokers and nonsmokers) doubled in women and continued unabated in men from the 1960s to the 1980s. Lung cancer surpassed coronary heart disease as the largest single contributor to smoking-attributable death among White middle-class smokers.

Adult↗
PubMed1994

Cigarette smoking: an independent risk factor for impotence?

The authors sought to determine whether current cigarette smoking was associated with impotence among middle-aged men. This is a secondary analysis of a cross-sectional survey of 4,462 US Army Vietnam-era veterans aged 31-49 years who took part in the Vietnam Experience Study in 1985-1986. The main outcome measurement was the odds ratio for reported impotence, which was calculated by comparing current smokers with nonsmokers while controlling for multiple confounders. The study sample consisted of 1,162 never smokers, 1,292 former smokers, and 2,008 current smokers. The prevalence of impotence was 2.2% among never smokers, 2.0% among former smokers, and 3.7% among current smokers (p = 0.005). The unadjusted odds ratio (OR) of the association between smoking and reported impotence was 1.8 (95% confidence interval (CI) 1.2-2.6). The association held even after adjustments were made for confounders, including vascular disease, psychiatric disease, hormonal factors, substance abuse, marital status, race, and age (OR = 1.5, 95% CI 1.0-2.2). Neither years smoked nor cigarettes smoked daily were significant predictors of impotence in current smokers. The authors concluded that, among the men in this study, a higher percentage of cigarette smokers reported impotence than did nonsmokers. This observation could not be totally explained by comorbidity factors related to smoking.

Adult↗
PubMed1994

Analysis of variations in mortality rates with small numbers.

OBJECTIVE: We present a Monte Carlo technique to evaluate if observed mortality rates differ from model-predicted rates for situations when the number of deaths is small. DATA SOURCES: We used Medicare hospital claims and model-predicted mortality rates from the Health Care Financing Administration (HCFA) for the 169 acute care hospitals in Georgia. The HCFA data provided model-predicted mortality rates at 30 days postadmission for 17 conditions and procedures of interest. The model-predicted rates calculated by HCFA were adjusted for patient factors, including demographic characteristics, principal diagnosis, and comorbidities. STUDY DESIGN: We test the hypothesis that model-predicted 30-day mortality rates at the 169 hospitals differ significantly from the observed 30-day mortality rates. Our approach uses a test statistic that resembles a chi-square statistic, and Monte Carlo simulations to estimate the distribution of the test statistic under the null hypothesis of no differences between the observed and predicted rates. We illustrate the method using two conceptually similar simulation models. We use results of the simulations to estimate p-values and compare these results with p-values associated with the nominal chi-square distribution. DATA EXTRACTION METHODS: We extracted 30-day observed and predicted mortality rates for Medicare beneficiaries for federal fiscal year 1990 for 17 conditions and procedures of interest. PRINCIPAL FINDINGS: If the number of deaths in some hospitals is small, p-values calculated using the nominal chi-square distribution can be misleading, thus supporting the usefulness of our simulation method. CONCLUSIONS: The Monte Carlo simulation is an appropriate approach to the analysis of hospital mortality or small area analysis for situations in which the number of deaths is small.

Analysis of Variance↗