Intracranial meningioma and ionizing radiation in medical and occupational settings

In a population-based case-control study of 200 cases and 400 controls in western Washington State, the authors assessed associations between meningioma and ionizing radiation in medical and occupational settings. No significant associations were observed for diagnostic studies or occupational settings, but associations were observed for radiation therapy to head or neck (odds ratio 3.7, 95% CI 1.5 to 9.5), especially for neoplastic conditions. Only four patients (2%) had meningiomas that followed high-dose cranial radiation.

Statin therapy and risk of dementia in the elderly: a community-based prospective cohort study

OBJECTIVE

To assess the association between statin therapy and risk of Alzheimer disease (AD) in a prospective cohort study with documented statin exposure and incident dementia.

METHODS

This is a prospective, cohort study of statin use and incident dementia and probable AD. A cohort of 2,356 cognitively intact persons, aged 65 and older, were randomly selected from a health maintenance organization (HMO), and were assessed biennially for dementia. Statin use was identified using the HMO pharmacy database. A proportional hazards model with statin use as a time-dependent covariate was used to assess the statin-dementia/AD association.

RESULTS

Among 312 participants with incident dementia, 168 had probable AD. The unadjusted hazard ratios (HRs) with statin use were 1.33 (95% CI 0.95 to 1.85) for all-cause dementia and 0.90 (CI 0.54 to 1.51) for probable AD. Adjusted corresponding HRs were 1.19 (CI 0.82 to 1.75) and 0.82 (CI 0.46 to 1.46). A subgroup analysis of participants with at least one APOE-epsilon4 allele who entered the study before age 80 produced an adjusted HR of 0.33 (CI 0.10 to 1.04).

CONCLUSION

Employing time-dependent proportional hazards modeling, the authors found no significant association between statin use and incident dementia or probable AD. In contrast, when the data were analyzed, inappropriately, as a case-control study, the authors found an OR of 0.55 for probable AD, falsely indicating a protective effect of statins. Study design and analytic methods may explain the discrepancy between the current null findings and earlier findings.

Prognosis in amyotrophic lateral sclerosis: a population-based study

BACKGROUND

Accurate information on prognosis of ALS is useful to patients, families, and clinicians.

METHODS

In a population-based study of ALS in western Washington, the authors assembled a cohort of 180 patients with incident ALS between 1990 and 1994. Information on potential prognostic factors was collected during an in-person interview. Patients also completed the Medical Outcomes Study Short Form 36 (SF-36). Vital status through December 1999 was known for all patients.

RESULTS

Median survival was 32 months from onset of symptoms and 19 months from diagnosis. The 5-year survival after diagnosis was 7%. Older age and female sex were strongly associated with poor survival. In multivariable Cox proportional hazards regression models, factors significantly and independently associated with a worse prognosis included older age, any bulbar features at onset, shorter time from symptom onset to diagnosis, lack of a marital partner, and residence in King County. Recursive partitioning identified age, time from symptom onset to diagnosis, and marital status as the strongest predictors of survival. Good summary scores for physical health on the SF-36, but not for mental health, were significantly associated with longer survival than poor scores.

CONCLUSION

These findings are consistent with other population-based studies of ALS and confirm its pernicious nature. Older age, female sex, any bulbar features at onset, short time from symptom onset to diagnosis, lack of a marital partner, and disease severity are key prognostic factors. Serial measurement of severity would likely improve predictions.

History of head trauma and risk of intracranial meningioma: population-based case-control study

A population-based case-control study in western Washington state was performed to assess the relation between head trauma and meningioma. Based on 200 case and 400 control subjects, head trauma was associated with an increased risk of meningioma (odds ratio = 1.83; 95% CI = 1.28, 2.62), especially head traumas occurring 10 to 19 years before reference date (odds ratio = 4.33; 95% CI = 2.06, 9.10). A dose-response relationship was present for number, but not severity, of head traumas. Whether the associations observed in this study are causal remains unclear.

Brain SPECT: a controlled, blinded assessment of intra-reader and inter-reader agreement

A detailed assessment of intra- and inter-reader variation in the interpretation of brain SPECT scans has been performed. A random sample was selected from scans performed at a community/teaching hospital in Seattle. Scans were interpreted independently by three experienced readers who were blinded to all patient information. Forty-eight scans were interpreted twice by each reader, for a total of 288 readings. Readers recorded detailed assessments of individual lesions and overall impressions using a standardized reporting form. Intra-observer agreement as reflected in per cent agreement for severity scores ranged from 65% to 100%. Intra-observer agreement on the 'overall impression' was very good for Alzheimer's pattern (kappa=0.73-1.00), and fair to good for the 'heterogeneous pattern' (kappa=0.30-0.63). Inter-observer agreement, as reflected in per cent agreement, ranged from 29% to 100%. Inter-observer agreement about the 'overall impression' was fair to moderate for Alzheimer's pattern (kappa=0.24-0.54) and was poor for the descriptors 'heterogeneous' and 'normal'. It is concluded that brain SPECT has great potential value in many important conditions. This study demonstrates a need for further work in the areas of pattern definition and reduction of observer variation.

DNA double-strand breaks in mouse kidney cells with age

A Biojector device fitted with a CO2 cartridge was used to prepare single cell suspensions from kidneys of 12-month- (middle-aged) and 24-month-old (old) C57B1/6 mice. Microgel electrophoresis of DNA from these cells revealed a modest but significant 7.3% increase (P = 0.04) in DNA double-strand breaks in old mice. This increase is equivalent to the DNA damage induced by 0.1 Gray of X-rays (5 double-strand breaks) in kidney cells of 10-month-old mice, as determined by a standard calibration curve. Greater DNA damage with aging was also positively correlated with higher levels of pathology in the kidneys.

Dietary soy isoflavone intake in older Japanese American women

OBJECTIVE

In a sample of older Japanese American women, we aimed to: (1) describe the most commonly consumed soy foods, (2) estimate dietary soy isoflavone intake, (3) describe characteristics associated with dietary soy isoflavone intake, and (4) compare our estimates with previously published estimates in other Japanese samples.

DESIGN

A 14-item soy food-frequency questionnaire was administered to older Japanese American women and responses were converted to quantitative estimates of soy isoflavones (genistein plus daidzein). Multiple regression was used to examine characteristics associated with dietary soy isoflavone intake, including self-reported lifestyle and cultural factors and dietary intake of various foods ascertained from a semi-quantitative food-frequency questionnaire. To compare our estimates with other samples, a review of the literature was conducted.

SETTING/SUBJECTS

Data are from 274 women aged 65+ years, recruited from a longitudinal cohort study of Japanese Americans in King County, Washington State.

RESULTS

The soy foods most commonly consumed were tofu (soybean curd), miso (fermented soybean paste) and aburaage (fried thin soybean curd). The mean intake of dietary soy isoflavones was 10.2 (standard deviation (SD), 12.4) mg day(-1), approximately a quarter to a half that of previously published estimates in Japanese samples. Dietary soy isoflavone intake was positively associated with speaking Japanese, the consumption of traditional Japanese dishes (kamaboko, manju and mochi), low-fat/non-fat milk and yellow/red vegetables, vitamin E supplement use, and walking several blocks each day. Dietary soy isoflavone intake was negatively associated with the consumption of butter.

CONCLUSIONS

The estimated dietary soy isoflavone intake in Japanese American women living in King County, Washington State was about a quarter to a half that of women living in Japan. Dietary soy isoflavone intake was associated with speaking Japanese and healthy lifestyle and dietary habits.

Air sampling at the chest and ear as representative of the breathing zone

Tracer gas concentrations were measured on a 60%-sized mannequin holding a pure sulfur hexafluoride source in its hands at waist height while it stood in a wind tunnel. Samplers were placed at the mannequin's mouth, in front of the ear, and at three chest locations at lapel level. Simultaneous 15-min time-weighted average samples were taken by drawing air into different sampling bags with sampling pumps. For the factorial study design, test conditions included cross-draft velocities of 10, 22, 47, and 80 ft/min; three mannequin orientations (facing to, side to, and back to cross-draft), and rotating speed through an 80 degrees arc (fast, slow, and no movement). Each study condition was tested twice. Concentrations at all sampling locations when the mannequin faced to the front and side were less than a tenth of the levels measured at the nose (Cnose) when the mannequin faced downstream. Higher velocities significantly increased concentration at the Back orientation and generally reduced it at the Side and Facing orientations. Concentrations at the nose were different from concentrations at other sites. For 34 of 36 samples the mean chest concentration (Cchest,) was higher than the Cnose (geometric mean three times higher). The ratio of ear (Cear) and Cnose varied with orientation. At the Back orientation, Cear, was lower than Cnose, whereas Cear was higher than Cnose at the Side and Facing to flow orientations. Velocity affected the ratios of concentrations. At the Back orientation, the chest sampler provided lower overestimates of Cnose, at higher velocities than at lower values. Mannequin movement, done only at the Back orientation, proved important only for the ear location. Results showed significant and substantial differences between concentrations at the nose and lapel. However, these findings should be interpreted with caution because a very dense tracer gas and an unheated, nonbreathing mannequin were used. In more realistic conditions, the findings probably would show far smaller differences in concentrations at different sampling sites.

Using census data and birth certificates to reconstruct the early-life socioeconomic environment and the relation to the development of Alzheimer's disease

The early-life environment and its effect on growth and maturation of children and adolescents are associated with several adult chronic diseases, including Alzheimer's disease. Because it is not feasible to collect information prospectively over the average life span, methods to reconstruct the early-life environment of the aged are necessary to evaluate these associations. In a community-based case-control study conducted in the United States, we collected U.S. census records and birth certificates to reconstruct the early-life socioeconomic environment of each elderly subject. Information was found on 82% of the available Alzheimer's disease cases (239 of 292) and 87% of the available controls (245 of 282). We investigated risk of Alzheimer's disease associated with father's occupation, parental age, household size, sibship size, and birth order. Subjects whose fathers were unskilled manual workers or laborers were at higher risk for Alzheimer's disease (odds ratio = 1.80, 95% confidence interval = 1.19--2.73). The risk of Alzheimer's disease was increased with increasing number of people in the household. We also evaluated whether subjects with the apolipoprotein epsilon 4 allele (APOE epsilon 4), a strong genetic risk factor that is not a necessary cause or a sufficient cause by itself for the development of Alzheimer's disease, were at higher risk than subjects who did not carry this allele. Among subjects with the APOE epsilon 4 allele whose fathers held lower-socioeconomic level occupations, the odds of developing Alzheimer's disease were higher (odds ratio = 2.35, 95% confidence interval = 1.07--5.16) compared with subjects without the allele (odds ratio = 1.40, 95% confidence interval = 0.78--2.52). Subjects carrying the APOE epsilon 4 allele alone have a threefold increased risk of Alzheimer's disease (odds ratio = 3.17, 95% confidence interval = 1.99--5.04). Compared with subjects with neither risk factor, subjects with both the genetic and the environmental risk factors (household size of seven or more and father's occupation being manual) had a relatively high risk of Alzheimer's disease (odds ratio = 14.8, 95% confidence interval = 4.9--46). The data suggest that APOE epsilon 4 may modify the associations between father's occupation, other early-life environmental factors, and development of Alzheimer's disease in late life.

Reliability of cognitive tests used in Alzheimer's disease

Assessment of cognitive status is a key component of monitoring Alzheimer's patients during the course of their illness. The reliability of a cognitive test is a measure of its reproducibility under replicate conditions. In the classical setting, reliability is defined in three ways: the ratio of the variance of the true scores to the variance of the observed scores; the correlation of observed scores on two parallel forms of the test, and the square of the correlation between the observed score and the true score. In the classical case of independence of true scores and measurement errors, the three definitions are equivalent. Estimation of reliability through analysis of variance techniques and construction of confidence intervals is accomplished when the true scores and errors are normally distributed. This paper examines a non-parametric, probabilistic estimate of reliability as the probability that, given a parallel test, the second set of scores has the same ranking as the first set. In the classical case there is a monotonic relationship between this measure and the reliability. This measure is also linked to Kendall's tau. The performance of the probabilistic measure is compared with the traditional measures in a variety of models, including those with bounded scales, and those with skewed distributions. The ideas are extended to the case of the reliability of change scores and to biased estimators of true scores. In this context truncation models and Bayes estimates of true scores are considered.

Early-life risk factors and the development of Alzheimer's disease

OBJECTIVE

To investigate the association of early-life factors with AD.

BACKGROUND

The early-life environment and its effect on growth and maturation of children and adolescents are linked to many adult chronic diseases (heart disease, stroke, hypertension, and diabetes mellitus), and these effects are also linked to maternal reproduction. AD may have an early-life link. The areas of the brain that show the earliest signs of AD are the same areas of the brain that take the longest to mature during childhood and adolescence. A poor-quality childhood or adolescent environment could prevent the brain from reaching complete levels of maturation. Lower levels of brain maturation may put people at higher risk for AD.

METHODS

In a community-based case-control study (393 cases, 377 controls), we investigated the association of early-life factors and AD. Early-life variables include mother's age at patient's birth, birth order, number of siblings, and area of residence before age 18 years. Patient education level and apolipoprotein E (APOE) genotypes were also included in the analysis.

RESULTS

Area of residence before age 18 years and number of siblings are associated with subsequent development of AD. For each additional child in the family the risk of AD increases by 8% (OR = 1.08, 95% CI = 1.01 to 1.15). More controls compared with cases grew up in the suburbs (OR = 0.45, 95% CI = 0.25 to 0.82). APOE epsilon 4 and the patient's education level did not confound or modify the associations.

CONCLUSIONS

The early-life childhood and adolescent environment is associated with the risk of AD.

Cross-sectional versus longitudinal estimates of cognitive change in nondemented older people: a CERAD study. Consortium to Establish a Registry for Alzheimer's Disease

OBJECTIVES

To investigate the effect of increasing age on cognition in nondemented older people.

DESIGN

A cross-sectional and longitudinal analysis.

PARTICIPANTS

A total of 454 control subjects for Alzheimer's cases from the cohort assembled by the Consortium to Establish a Registry for Alzheimer's Disease (CERAD).

MEASUREMENT

The Mini-Mental State Examination (MMSE) to assess cognitive function.

RESULTS

Cross-sectional estimates were derived by generalized linear models and longitudinal estimates by generalized estimating equations. The cross-sectional model indicated a small but significant decline in MMSE of -.4 points per 10 years. The longitudinal model indicated a small but significant increase in MMSE of about +.6 points per 10 years. Evidence of an early learning effect and nonrandom dropout exists.

CONCLUSIONS

The question of "normal" aging can be approached by considering cross-sectional information and, usually separately, longitudinal information. This study does both using recently developed statistical methods. We conclude that there is a small but significant decline in scores on the MMSE with increasing population age. The effect can be masked in longitudinal cohorts by a learning effect (especially early in follow-up) and other factors associated with repeated testing.

Evaluation of a public-private certified nurse-midwife maternity program for indigent women

OBJECTIVES

This study assessed the impact of a public-private certified nurse-midwife program on prenatal and delivery outcomes among medically indigent women.

METHODS

A population-based quasi-experimental design was used to compare 1 intervention county with 2 nonintervention counties.

RESULTS

The program significantly reduced the number of women who received no prenatal care and the risk of acquiring less than adequate prenatal care. Reductions in the proportion of infants born premature or with low birth-weights were of borderline significance. The use of induction and/or stimulation of labor was statistically elevated.

CONCLUSIONS

These results suggest that the intervention program was instrumental in reducing some, but not all, negative prenatal and delivery outcomes.

Risk of amyotrophic lateral sclerosis and history of physical activity: a population-based case-control study

OBJECTIVE

To assess in greater detail than previous studies the purported association between a history of physical activity and amyotrophic lateral sclerosis (ALS).

METHODS

A population-based case-control study was used to identify risk factors for ALS. Case patients were from 3 counties of western Washington State who were newly diagnosed as having ALS by a neurologist. Two control subjects matched with each case patient for sex and age within 5 years were identified by random digit telephone dialing or random selection from Medicare eligibility lists. All subjects underwent an in-person structured interview including detailed information about physical activity before a reference date, which was the month and year the case patient was diagnosed as having ALS. Various measures of physical activity both at work and leisure time were evaluated using conditional logistic regression taking into account the matching for sex and age.

RESULTS

One hundred seventy-four case patients and 348 control subjects participated in the study. Physical activity was not significantly different between case patients and controls--whether at work, leisure time or both combined, and whether during a person's lifetime (from 10 years before reference date back to age 15 years) or during specific decades before reference date. An exception was that case patients reported having participated in organized sports in high school slightly more frequently than control subjects (odds ratio, 1.52; 95% confidence interval, 1.03-2.25).

CONCLUSION

A history of physical activity has little, if any, effect on the risk of ALS.

Behavioral changes following participation in a home health promotional program in King County, Washington

This study examined behavioral changes in households after participation in a home environmental assessment. Home assessment visits by a trained coach, which involved a walk-through in the home with the home residents, were conducted in 36 homes. The walk-through included a list of recommended behavioral changes that the residents could make to reduce their exposures to home pollutants in areas such as dust control, moisture problems, indoor air, hazardous household products, and hobbies. Recruited households were surveyed 3 months after the home assessment to evaluate their implementation of the recommendations. Following the home visits, 31 of 36 households reported making at least one behavioral change, and 41% of the recommendations made by the volunteer coaches were implemented. In conclusion, this study found that the majority of the households who participated in the home assessment reported implementing at least one recommendation. This home health promotional method was effective in influencing behavioral changes.

Mesothelioma surveillance to locate sources of exposure to asbestos

To determine whether there were previously unrecognized sources of asbestos exposure in British Columbia, incident mesothelioma cases (n = 51) and population-based controls (n = 154) were interviewed about their occupational histories and asbestos exposures. The following occupations were at elevated risk: sheet metal workers (OR = 9.6, 95% CI: 1.5-106), plumbers and pipefitters (OR = 8.3, 95% CI: 1.5-86), shipbuilding workers (OR = 5.0, 95% CI: 1.2-23), painters (OR = 4.5, 95% CI: 1.0-24), welders (OR = 3.9, 95% CI: 0.8-22), gardeners (OR = 3.9, 95% CI: 0.8-22), bricklayers (OR = 3.5, 95% CI: 0.9-14), miners (OR = 3.4, 95% CI: 0.9-13), machinists (OR = 3.2, 95% CI: 1.0-11), construction foremen (OR = 3.1, 95% CI: 0.9-11), and electricians (OR = 3.0, 95% CI: 0.8-12). In a reanalysis excluding subjects who worked in occupations or processes considered strongly a priori at risk, three groups remained of interest: non-asbestos miners (OR = 9.6, 95% CI: 1.8-53), bricklayers (OR = 5.4, 95% CI: 1.0-28), and construction labourers (OR = 2.8, 95% CI: 0.7-10.6).

Consortium to establish a registry for Alzheimer's disease: development, database structure, and selected findings

The Consortium to Establish a Registry for Alzheimer's Disease (CERAD) was funded in 1986 by the National Institute on Aging to develop standardized assessments for patients with Alzheimer's disease (AD). Since that time, CERAD has developed and evaluated clinical and neuropsychological test batteries, a neuroimaging protocol, and an assessment of the neuropathological findings of the brains of these patients at autopsy. Approximately 1,200 carefully screened patients with AD and 450 control subjects were evaluated using these instruments at 24 major medical centers around the United States. Annual follow-up observations of these subjects were made for up to eight years. Autopsy examinations of the brain were done in over half of the deceased cases and the clinical diagnosis of AD was confirmed in 85 percent of them. This article outlines the procedures used for identifying the clinical sites, the entry and annual evaluations of patients and control subjects, the collection and analysis of data at a central Methodology and Data Management Center, and evaluation of the CERAD measures. We also present selected data from the 50 or so peer-reviewed papers published to date, with particular emphasis on findings from African-American patients with AD, and related policy implications.

Occupational exposures and amyotrophic lateral sclerosis. A population-based case-control study

This population-based case-control study was conducted in three countries in western Washington State to evaluate associations between workplace exposures and the risk of amyotrophic lateral sclerosis (ALS). Cases (n = 174) were all newly diagnosed with ALS by neurologists during 1990-1994, and controls (n = 348), who were matched according to age (+/-5 years) and sex, were identified via random-digit dialing or Medicare enrollment files. Four industrial hygienists blindly assessed detailed lifetime job histories for exposures to metals, solvents, and agricultural chemicals. Case-control comparisons were made for jobs held between 15 years of age and 10 years prior to the cases' dates of diagnosis. After adjustment for age and education, ever exposure to agricultural chemicals was associated with ALS (odds ratio (OR) = 2.0, 95% confidence interval (CI) 1.1-3.5); this association was observed separately in men (OR = 2.4, 95% CI 1.2-4.8) but not in women (OR = 0.9, 95% CI 0.2-3.8). Among men, the odds ratio for low exposure to agricultural chemicals (below the median level for exposed controls) relative to no exposure was 1.5 (95% CI 0.4-5.3), and for high exposure, it was 2.8 (95% CI 1.3-6.1) (p for trend = 0.03). Similar analyses based on the panel's assessment of exposures to metals and solvents showed no associations. These findings suggest an association between ALS and agricultural chemicals in men.

Surveillance of nasal and bladder cancer to locate sources of exposure to occupational carcinogens

OBJECTIVE

To locate sources of occupational exposure to nasal and bladder carcinogens for surveillance follow up in British Columbia, Canada.

METHODS

Incident cases of nasal cancer (n = 48), bladder cancer (n = 105), and population based controls (n = 159) matched for sex and age, were interviewed about their jobs, exposures, and smoking histories. Odds ratios (ORs) were calculated for 57 occupational groups with stratified exact methods to control for age, sex, and smoking.

RESULTS

Occupational groups at increased risk of nasal cancer included: textile workers (six cases, OR 7.6); miners, drillers, and blasters (six cases, OR 3.5); welders (two cases, OR 3.5); pulp and paper workers (three cases, OR 3.1); and plumbers and pipefitters (two cases, OR 3.0). Nasal cancer ORs were not increased in occupations exposed to wood dust, possibly due to low exposures in local wood industries. Strongly increased risks of bladder cancer were found for sheet metal workers (four cases, OR 5.3), miners (19 cases, OR 4.5), gardeners (six cases, OR 3.7), and hairdressers (three cases, OR 3.2). Among occupations originally considered at risk, the following had increased risks of bladder cancer: painters (four cases, OR 2.8); laundry workers (five cases, OR 2.3); chemical and petroleum workers (15 cases, OR 1.8); machinists (eight cases, OR 1.6); and textile workers (three cases, OR 1.5).

CONCLUSIONS

Occupational groups with increased risks and three or more cases with similar duties were selected for surveillance follow up. For nasal cancer, these included textile workers (five were garment makers) and pulp and paper workers (three performed maintenance tasks likely to entail stainless steel welding). For bladder cancer, these included miners (12 worked underground), machinists (five worked in traditional machining), hairdressers (three had applied hair dyes), and laundry workers (three were drycleaners).

Pulmonary function and respiratory symptoms in forest firefighters

This study evaluated effects on respiratory health of forest firefighters exposed to high concentrations of smoke during their work shift. This is the first study of cross-shift respiratory effects in forest firefighters conducted on the job. Spirometric measurements and self-administered questionnaire data were collected before and after the 1992 firefighting season. Seventy-six (76) subjects were studied for cross-shift and 53 for cross-season analysis. On average, the cross-season data were collected 77.7 days after the last occupational smoke exposure. The cross-shift analysis identified significant mean individual declines in FVC. FEV1, and FEF25 75. The preshift to midshift decreases were 0.089 L, 0.190 L, and 0.439 I/sec. respectively, with preshift to postshift declines of 0.065 L, 0.150 L, and 0.496 L/sec. Mean individual declines for FVC, FEV1 and FEF25 75 of 0.033 L, 0.104 L, and 0.275 I/sec. respectively, also were noted in the cross-season analysis. The FEV1 changed significantly (p < 0.05). The use of wood for indoor heat also was associated with the declines in FEV1. Although annual lung function changes for a small subset (n = 10) indicated reversibility of effect, this study suggests a concern for potential adverse respiratory effects in forest firefighters.

Counting plaques and tangles in Alzheimer's disease: concordance of technicians and pathologists

Our primary aim is to provide a descriptive approach to the analysis of counts of plaques and tangles by different readers. We wanted to find out whether subjects with minimal training can count plaques and tangles in histological specimens of patients with Alzheimer's disease and controls. Two experienced neuropathologists trained three student helpers to recognize plaques and tangles in slides obtained from autopsy material. After training, the students and pathologists examined coded slides from patients with Alzheimer's disease and controls. Some of the slides were repeated to provide an estimate of reliability. Each reader read four fields which were averaged to obtain estimates of plaque and tangle counts. Raters are compared on four aspects of concordance: location, scale, precision and accuracy. Precision and accuracy are combined to provide an estimate of concordance. We conclude that subjects with minimal training can be taught to count plaques and tangles. Concordance with the neuropathologists was somewhat greater for tangles. This paper also provides a methodology for comparing raters.

Randomized trial of leaving messages on telephone answering machines for control recruitment in an epidemiologic study

To determine whether leaving messages on answering machines would aid control recruitment via random-digit telephone dialing, a randomized trial was conducted during 1992-1994 involving 1,323 western Washington households with answering machines. For the experimental group, a message was left informing them about the study and promising a call-back; for the control group, no message was left. Leaving a message increased the response rate by about 20 percentage points (p = 0.002). More households were successfully screened for eligible controls, and individuals found eligible were more likely to participate. Leaving a message can help to improve response rates in telephone surveys.

Incidence of amyotrophic lateral sclerosis in three counties in western Washington state

We conducted a population-based study of amyotrophic lateral sclerosis (ALS) in King, Pierce, and Snohomish counties in western Washington state. Between April 1, 1990 and March 31, 1995, neurologists diagnosed 235 patients with ALS, including 127 men (54%) and 108 women (46%). The incidence rate, age-adjusted to the 1990 total U.S. population, was higher for men at 2.1 per 100,000 per year (95% CI, 1.3 to 2.9) than for women at 1.9 (95% CI, 1.1, 2.7) and increased with age for both men and women. These incidence rates are consistent with other studies from northern latitudes.

Geographically overlapping Alzheimer's disease registries: comparisons and implications

In the medical and epidemiologic literature, a registry denotes a data base in which registrants share some common characteristic such as disease category. One criticism of registries is that they frequently collect subjects in a haphazard fashion and, hence, are "nonrepresentative of the population purportedly being represented." In this report, we compare two registries: an incident-based Alzheimer's Disease Patient Registry (ADPR) recruiting subjects for epidemiologic studies from a large health maintenance organization; and an Alzheimer's Disease Research Center (ADRC) registry recruiting subjects for phenomenologic, biologic, and pharmacologic studies. While these registries share personnel, overlap geographically, and use similar diagnostic procedures, they differ substantially in their missions and resulting recruitment strategies. We compared these registries with respect to demographic characteristics and cognitive features at subject entry. Subjects enrolled in the incident-based registry are older and report shorter time between symptom onset and recruitment. They are less demented and mirror the general population demographically more closely than do subjects in the other registry. The ADRC registry contains a much greater proportion of subjects with higher educational attainment.

Solvent exposure as a risk factor for Alzheimer's disease: a case-control study

This case-control study investigates whether history of organic solvent exposure is associated with increased risk of Alzheimer's disease. The study base includes about 23,000 persons aged 60 years or more from the local membership of a health maintenance organization in Seattle, Washington, who entered the study between 1987 and 1992. Probable Alzheimer's disease cases (n = 193) who had presented with new dementia symptoms were identified, enrolled, and diagnosed by our Alzheimer's Disease Patient Registry following standardized criteria. Control subjects (n = 243), free of dementia and neurologic disease causing dementia, were selected randomly from the study base and frequency matched to cases for age and sex. Proxy informants provided specific solvent exposure history as well as job descriptions likely to involve solvent use as part of a comprehensive risk factor interview. Kappa statistics indicated substantial agreement for control-control proxy solvent responses. History of exposure to one or more solvent groups (benzene and toluene; phenols and alcohols; ketones; other solvents) yielded an adjusted Alzheimer's disease odds ratio of 2.3 (95 percent confidence interval 1.1-4.7); among males only, it increased to 6.0 (95% confidence interval 2.1-17.2). Thus, past exposure to organic solvents may be associated with onset of Alzheimer's disease.

The effect of diagnosing Alzheimer's disease on frequency of physician visits: a case-control study

OBJECTIVE

Two groups of elderly subjects were studied to see whether patterns of visits to physicians changed after one group received the diagnosis of Alzheimer's disease.

DESIGN

Case-control study.

SETTING

Health maintenance organization (HMO).

PATIENTS/PARTICIPANTS

Two groups of ambulatory subjects (mean age 77 years) were enrolled from an HMO population for this case-control study: 120 cases had probable Alzheimer's disease diagnosed at enrollment, and another 120 cognitively intact controls with similar comorbidity were enrolled after being frequency-matched for age and gender. Exclusion criteria were nursing home admission and death during the study period.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Medical records were examined for a four-year period: two years prior to and two years following enrollment and diagnosis. Physician visits declined slightly after enrollment for the persons receiving the diagnosis of Alzheimer's disease [17.5/2 years prior vs 16.5/2 years after (NS)], whereas visits increased over time for the controls [13.7/2 vs 16.3/2 (p < 0.05)], hence the rates were similar after enrollment [16.5 vs 16.3 (NS)]. The proportion of subjects with fewer visits during the period after enrollment was higher among the cases than it was among the controls [54% vs 37%; odds ratio = 2.0 (95% confidence interval = 1.6, 3.1)]. Hospitalizations and emergency department use did not change significantly after enrollment.

CONCLUSIONS

Physician visit frequency was high before, then decreased after, demented patients received their diagnosis, approaching the frequency in a control population without dementia. This phenomenon cannot be accounted for by nursing home placement, comorbidity, or mortality. Increased hospitalization and emergency department use did not ensue after diagnosis.

Lack of cholinergic regulation of vasopressin and norepinephrine responses to hypertonic saline in humans

In vitro studies in hypothalamic-pituitary explants in the rat have suggested cholinergic mediation of arginine vasopressin (AVP) osmoregulation. In this study we attempted to demonstrate, in humans, cholinergic mediation of AVP osmoregulation. Specifically, we tested the hypothesis that the plasma AVP response to an osmolar stimulus would be attenuated by pharmacologic blockade of central nervous system muscarinic or nicotinic receptors in humans. We also evaluated the effects of cholinergic blockade on the norepinephrine (NE) response to an osmolar stimulus. Young normal males underwent hypertonic saline infusion following administration of the centrally active muscarinic antagonist scopolamine or the centrally active nicotinic antagonist mecamylamine. Neither mecamylamine nor scopolamine affected the AVP response to hypertonic saline infusion. Mecamylamine reduced NE concentrations in a dose-dependent manner, but did not affect the slope of the NE increase during hypertonic saline infusion. In a second experiment, we evaluated the effects of scopolamine and mecamylamine on the AVP and NE responses to physostigmine, a cholinesterase inhibitor which stimulates AVP release into plasma through a non-osmolar central nervous system cholinergic mechanism. Scopolamine eliminated the AVP response to physostigmine. Mecamylamine reduced NE concentrations both before and after scopolamine administration but did not affect the slope of the AVP response. These results fail to support cholinergic regulation of the AVP response to osmolar stimulation in humans.

Aspartame ingestion and headaches: a randomized crossover trial

To examine whether ingestion of aspartame is associated with headaches, we conducted a double-blind crossover study using volunteers with self-identified headaches after using aspartame. Of the 32 subjects randomized to receive aspartame (approximately 30 mg/kg/d) and placebo in a two-treatment, four-period crossover design, 18 completed the full protocol, seven completed part of the protocol before withdrawing due to adverse effects, three withdrew for other reasons, two were lost to follow-up, one was withdrawn due to noncompliance, and one withdrew and gave no reason. Each experimental period was 7 days long. Subjects reported headaches on 33% of the days during aspartame treatment, compared with 24% on placebo treatment (p = 0.04). Subjects who were "very sure" prior to the study that aspartame triggered some of their headaches reported larger treatment differences (aspartame = 0.37 headache-days, placebo = 0.18 headache-days; p < 0.001) than subjects who were "somewhat sure" (aspartame = 0.29 headache-days, placebo = 0.22 headache-days; p = 0.51) or "not sure" (aspartame = 0.33 headache-days, placebo = 0.39 headache-days; p = 0.51). There was no significant treatment difference in the length or intensity of headaches or in the occurrence of side effects associated with the headaches. This experiment provides evidence that, among individuals with self-reported headaches after ingestion of aspartame, a subset of this group report more headaches when tested under controlled conditions. It appears that some people are particularly susceptible to headaches caused by aspartame and may want to limit their consumption.

Subarachnoid hemorrhage and hormonal factors in women. A population-based case-control study

OBJECTIVE

To determine the degree to which endogenous and exogenous hormonal factors influence the risk for subarachnoid hemorrhage in women.

DESIGN

A population-based case-control study.

SETTING

King County, Washington.

PARTICIPANTS

103 women with an incident, spontaneous subarachnoid hemorrhage and 2 age- and sex-matched controls per case-patient who were identified through random-digit dialing.

MEASUREMENTS

Information on exposures was collected during in-person interviews of case-patients, controls, and their surrogates.

RESULTS

Premenopausal women, especially those without a history of smoking or hypertension, were at a reduced risk for subarachnoid hemorrhage compared with age-matched postmenopausal women (odds ratio, 0.24; 95% CI, 0.09 to 0.68). The use of hormone replacement therapy was associated with a reduced risk (odds ratio, 0.47; CI, 0.26 to 0.86); the reduction was significantly greater in women who had smoked than in those that had never smoked. Of the 23 premenopausal case-patients, 74% were either menstruating when hemorrhaging occurred or had had their last menstrual period 21 or more days before hemorrhaging compared with the expected 43% (difference, 31%; CI, 4% to 58%).

CONCLUSIONS

Premenopausal women are at reduced risk for subarachnoid hemorrhage, especially those without a history of smoking or hypertension. Hormone replacement therapy reduced the risk only in postmenopausal women who had ever smoked. Among women still menstruating, the risk for hemorrhage was greatest in the perimenstrual period.

Postmenopausal estrogen replacement therapy and the risk of Alzheimer's disease: a population-based case-control study

Preliminary animal and human data suggest that estrogens may be protective against Alzheimer's disease in women. In a population-based case-control study at Group Health Cooperative of Puget Sound, Seattle, Washington, the authors compared the exposure of estrogen replacement therapy of 107 female Alzheimer's disease cases with 120 age- and sex-matched controls by using computerized pharmacy data. The cases were obtained from the Alzheimer's Disease Patient Registry of the University of Washington, Seattle, Washington, which is based on the enumerated health plan population from 1987 to 1992. Newly recognized cases of probable Alzheimer's disease according to standardized diagnostic criteria were ascertained, evaluated, and enrolled in the Registry. The controls were selected from the same defined population by stratified random sampling. When the authors applied logistic regression, ever use of estrogens did not show an association with Alzheimer's disease (adjusted odds ratio = 1.1, 95 percent confidence interval 0.6-1.8). Oral and vaginal estrogens yielded similar results. In conclusion, this study provides no evidence that estrogen replacement therapy has an impact on the risk of Alzheimer's disease in women.

Interlaboratory comparison of neuropathology assessments in Alzheimer's disease: a study of the Consortium to Establish a Registry for Alzheimer's Disease (CERAD)

Concerns about intercenter variation in methods and interpretation prompted CERAD investigators to examine standardization of the neuropathological assessment of Alzheimer's disease (AD). Contiguous frontal lobe sections derived from autopsy brains of eight patients clinically diagnosed as having probable AD and two cognitively normal individuals were distributed to 24 neuropathologists from 18 medical centers in the United States and Canada. Using their routine staining method(s), neuropathologists determined the rank order of severity of AD neuropathology in these cases, as well as semiquantitative and quantitative senile plaque and neurofibrillary tangle frequencies. Ranking of the ten cases revealed 75% inter-rater reliability among the 24 raters. Semiquantitative analyses showed reasonable inter-rater agreement, whereas quantitative measures yielded significant differences between raters for plaque and tangle counts (p < 0.0001). These differences reflected variation in stain sensitivity, staining technique (even when the same stain was used), and interpretation of the histological findings. Ratings on the cases with the highest proportions of diffuse plaques showed the greatest dependence upon stain sensitivity and variability in interpretation. This study indicates that greater attention to quality improvement is needed for the neuropathological evaluation of AD, particularly when pooling data in multicenter studies such as CERAD.

Symptom patterns and comorbidity in the early stages of Alzheimer's disease

OBJECTIVE

To learn whether patients with early Alzheimer's disease tend to under-report or over-report symptoms and to compare their comorbidity with non-demented patients.

DESIGN

Case Control Study in a population-based dementia registry.

SETTING AND PATIENTS

Three groups of subjects (mean age 76) were enrolled from an HMO base population: 154 cases had clinically diagnosed probable Alzheimer's disease, 92 subjects were found to be not demented although they had complaints of cognitive impairment, and another 129 cognitively intact controls were enrolled after frequency-matching for age and sex.

MEASUREMENTS AND RESULTS

Medical records were examined for the 2 years prior to enrollment. Symptoms suggestive of cognitive impairment were evident 7.8 months prior to enrollment (median 6 months) in 95% of cases, in 77% of the not demented subjects, and in 6% of controls. After corrections for multiple comparisons, only symptoms of cognitive impairment were more frequent in cases, whereas several common symptoms not suggestive of cognitive impairment (eg, gastrointestinal discomfort, joint pain, vision problems) occurred more often in controls and the not demented group, even though comorbidity was similar among all three groups (Charlson Index mean scores: case = 0.7, not demented = 0.7, control = 0.5).

CONCLUSIONS

Persons with Alzheimer's disease do complain of symptoms clearly related to cognitive impairment early in the course of illness, but may under-report common symptoms not suggestive of cognitive impairment, even though their comorbidity is similar to patients without dementia.

Completeness and accuracy of interview data from proxy respondents: demographic, medical, and life-style factors

To evaluate the quality of exposure data provided by proxy respondents, we used a dual interview protocol in a case-control study of subarachnoid hemorrhage. All control subjects and their proxy respondents were interviewed (N = 283 control-proxy pairs), as were the cases who were able to provide their own information and their proxy respondents (N = 68 case-proxy pairs). The reliability of proxy-derived data was excellent for demographic and body habitus measures (kappa or intraclass correlation range = 0.86-0.99), and all aspects of cigarette smoking history (range = 0.79-0.93). Proxy reliability was somewhat lower for questions regarding medications and hormone preparations (range = 0.55-0.88), alcohol consumption (range = 0.52-0.82), and recreational physical activity (range = 0.55-0.67). Proxy reliability varied according to the relationship of the proxy to the index subject. Relative to the index subjects, proxy respondents tended to underreport the presence or level of exposure. For most exposures, odds ratios computed with proxy-derived data were similar in magnitude to odds ratios obtained with index subject data; important bias due to differential nonresponse or differential misclassification was suggested only for questions regarding hormone replacement therapy. Epidemiologic studies that rely on proxy respondents may require more subjects to offset the effect of nondifferential nonresponse and misclassification on the precision of effect estimates.

The consortium to establish a registry for Alzheimer's disease (CERAD). Part IV. Rates of cognitive change in the longitudinal assessment of probable Alzheimer's disease

Reliable information on rate of progression of cognitive impairment in probable Alzheimer's disease (AD) is important for evaluating possible beneficial effects of therapeutic agents and in planning long-term care for patients with this chronic illness. However, wide variability exists in published rates of change for psychometric measures of the dementing process, and there is need for an accurate analysis of large numbers of persons with the disorder studied over long periods. Utilizing the large, well-characterized sample of the Consortium to Establish a Registry for Alzheimer's Disease and employing a least squares regression method to adjust for different levels of impairment and periods of observation, we report rates of change on the Short Blessed Test, Mini-Mental State Examination, Blessed Dementia Scale, Clinical Dementia Rating, and other cognitive measures in 430 patients with probable AD (mean age at entry = 70.9 +/- 8.0 SD years) studied for up to 4 years. We found that rate-of-change determinations are less reliable when the observation period is 1 year or less, that dementia progression may be nonlinear when described by certain measures, and that simple change scores do not accurately characterize the rate of decline. We also found that rate of progression in AD is determined by the severity of cognitive impairment: the less severe the dementia, the slower the rate of decline.

Clinical course of spontaneous subarachnoid hemorrhage: a population-based study in King County, Washington

Over 2 years, we identified 171 patients in King County, Washington, experiencing an incident subarachnoid hemorrhage and characterized their clinical course and outcome. Most (65%) were women and most (68%) were under age sixty-five. Only five died without medical attention. The remaining 166 patients were hospitalized and had CTs of the head. Of these, 103 underwent aneurysm surgery, 40 developed acute hydrocephalus, 32 had symptomatic vasospasm, and 30 re-bled. Sixty-eight percent (68%) survived to 1 month after the bleed and 62% to 1 year. Independent predictors of good recovery by 1 month after the bleed included youth, a high score on the admission Glasgow Coma Scale, and absence of blood on the first CT. In this population-based series, at 1 month after the bleed, approximately one-third of patients were dead, one-third had neurologic deficits, and one-third were doing well.

Relationship between cigarette smoking and Alzheimer's disease in a population-based case-control study

We investigated whether cigarette smoking is negatively associated with Alzheimer's disease (AD) in a population-based, frequency-matched, case-control study of 152 AD patients and 180 controls. Ever having smoked was associated with lower risk of AD (adjusted odds ratio = 0.61; 95% confidence interval: 0.37-0.99). Additional multivariate analyses demonstrated that education and history of hypertension modified this association. The direction of the modification was for higher education level and history of hypertension to further reduce the risk. The "dose-response" pattern showed the greatest risk reduction among those who smoked least and suggests a biologic mechanism of a dose-dependent up-regulation of nicotinic (cholinergic) brain receptors. These data, although consistent with current opinion about pathophysiology of AD, do not suggest smoking should be used as a preventive strategy for AD.

Relationship between epidemiologic risk factors and clinicopathologic findings in the sudden infant death syndrome

The risk of sudden infant death syndrome (SIDS) is said to be enhanced by factors such as prematurity, low birth weight, and perinatal distress. The significance of risk factors for SIDS research was questioned because the majority of SIDS victims seem to lack them. Therefore, postmortem records of 1144 infants who died suddenly and unexpectedly in King County, Washington, over a 25-year period were studied. Deaths were classified as "explained" if a cause was apparent, "classic" SIDS if the history and autopsy were unrevealing or, where the diagnosis of SIDS was doubtful, as "probable" or "possible" SIDS. The infants' birth certificates were compared with those of 3647 infants born during a similar period. Seventy-nine deaths (7%) were explained. The 1065 previously certified as SIDS were reclassified classic SIDS (82%), probable SIDS (13%), and possible SIDS (5%). Low birth weight, small size for gestational age, prematurity, and low 5-minute Apgar scores each form a "continuum"; the possible-SIDS group had the highest proportion of such infants, followed by the probable- and classic-SIDS groups, which exhibit extensive overlap with the control population. A 5-minute Apgar score of less than 7 and delayed postnatal growth rate are not risk factors for classic SIDS. Risk factors are more prevalent in SIDS infants where the diagnosis may be doubtful. The great majority of SIDS victims possess fewer risk factors. To avoid the bias of confounding variables, SIDS research should focus on as "pure" a SIDS population as is possible.

Respiratory epithelial cell invasion by group B streptococci

Group B streptococci (GBS) are the most common cause of pneumonia and sepsis during the neonatal period; however, the pathogenesis of this infection is poorly understood. We investigated the ability of GBS to enter epithelial cells in culture. Two strains of GBS were capable of invading immortalized respiratory epithelial cell lines in vitro at different levels, suggesting strain differences in invasiveness. Intracellular replication was not observed. Invasion required actin microfilaments but not microtubular cytoskeletal elements. Active bacterial protein, DNA, and RNA syntheses were required for invasion. These findings are consistent with our previous observation of intracellular GBS in the lungs of infected primates. We hypothesize that this organism may access the bloodstream by direct invasion of the epithelial cell barrier.

Cigarette smoking, alcohol use, and subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Subarachnoid hemorrhage remains a devastating disease. Identification of etiologic risk factors would allow the possibility of prevention.

METHODS

We conducted a population-based case-control study in King County, Washington. Patients whose bleeds originated from a source other than an aneurysm were excluded. Two age- and gender-matched control subjects were identified for each case through random digit telephone dialing. A standardized in-person interview was conducted with the patient whenever possible, a proxy respondent for the case in all instances, the two control subjects, and their proxies. Analyses involved conditional logistic regression taking into account matching on age, gender and respondent type.

RESULTS

Over 2 years, 169 cases were identified, and 149 participated in the case-control study. Compared with those who never smoked, the odds ratio for current heavy smokers (greater than 20 cigarettes/day) was 11.1 (95% confidence interval [CI], 5.0-24.9); for current light smokers (less than or equal to 20 cigarettes/day), 4.1 (95% CI, 2.3-7.3); and for former smokers, 1.8 (95% CI, 1.0-3.2). The risk associated with smoking was greatest in the 3 hours after a cigarette (odds ratio [OR] = 7.0; 95% CI, 3.7-13.1) and then fell, not reaching the risk in those who had never smoked until more than 10 years had passed since the last cigarette. Heavy alcohol use (greater than 2 drinks/day) was also associated with bleeds (OR = 2.2; 95% CI, 0.9-5.1, after adjusting for smoking status). These associations were not substantially altered after adjusting for several possible confounding factors, including a history of hypertension.

CONCLUSIONS

Cigarette smoking and heavy alcohol use are associated with the occurrence of subarachnoid hemorrhage.

Increased platelet membrane fluidity as a diagnostic marker for Alzheimer's disease: a test in population-based cases and controls

To test whether increased platelet membrane fluidity as measured by decreased steady state fluorescence anisotropy (rs) of diphenylhexatriene is a biologic/diagnostic marker for Alzheimer's disease (AD), we enrolled 95 clinically diagnosed, probable AD cases from our Alzheimer's Disease Patient Registry and 133 control subjects of similar age and sex randomly selected from the same population base as the cases. We measured rs in platelet membranes following published assay procedures. Laboratory personnel and investigators were blind to the identity of the samples; cases and controls were assayed in random order. Our analyses showed that the distributions of rs values were unimodal and similar for cases and controls. The overall mean differences (control mean-case mean) for the two established assay methods tested were 0.0011 and 0.0003. A nonparametric Wilcoxon rank sum test also showed no difference between cases and controls. Multivariate analysis adjusted for the significant effects of the processing date and analysis platelet recovery led to a final model with the adjusted mean difference of 0.0007 for the principal method. Increased platelet membrane fluidity is not an antemortem diagnostic or biologic marker for AD in our population.