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Biomedical subjects

W T Longstreth

Publications and source records attributed to W T Longstreth.

At least 127 records · Page 7Linked to original sources
PubMed1997

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.

Adolescent↗
PubMed1997

Factor V Leiden (resistance to activated protein C) increases the risk of myocardial infarction in young women.

Factor V Leiden (factor V Arg506Gln), the genetic defect underlying resistance to activated protein C, is the most common risk factor for venous thrombosis. The relationship between this genetic abnormality and arterial disease is still unresolved. To assess whether factor V Leiden increases the risk of myocardial infarction (MI), we conducted a population-based case-control study among women 18 to 44 years of age in western Washington state. We included 84 women with first MI and 388 control women, ie, women residing in the same area in the same age range without MI (n = 388). The control women were contacted by random digit dialing. Data on risk factor status were collected via personal interview, and data on the factor V genotype via polymerase chain reaction techniques. The factor V Leiden mutation was found more often in women with MI (10%) than among controls (4%). The odds ratio for MI was 2.4 [95% confidence interval (CI) 1.0 to 5.9]. The risk was increased fourfold (CIgs 1.2 to 12.1) when adjusted for major cardiovascular risk factors. Among nonsmokers the factor V Leiden mutation had little effect (odds ratio 1.1, CI95 0.1 to 8.5), whereas it had a large effect among smokers (odds ratio 3.6, CI95 0.9 to 14.4), which, because smoking was itself a strong risk factor for MI, led to an odds ratio for smoking carriers of the mutation that was 32-fold increased compared with nonsmoking noncarriers. We conclude that factor V Leiden increases the risk of MI in young women. This effect seems to be confined largely to current smokers.

Adult↗
PubMed1997

Hearing loss and antiretroviral therapy in patients infected with HIV-1.

OBJECTIVE: To explore the association between hearing loss and antiretroviral therapy in human immunodeficiency virus type 1 (HIV-1)-infected persons. DESIGN: Case-control study. SETTING: University-based HIV clinic. PARTICIPANTS: Volunteer sample of 99 HIV-infected patients. INTERVENTIONS: Standardized interview focusing on risks for hearing loss, review of clinic pharmacy records, and hearing tests by portable audiometry. MAIN OUTCOME MEASURE: Hearing loss, defined as threshold of more than a 25-dB hearing level at 4000 Hz in 1 or both ears. RESULTS: Hearing loss was common, seen in 29 subjects (29%). It was significantly associated with age and history of ear infection and tended to be more common in subjects prescribed antiretroviral agents. An interaction existed between age and antiretroviral therapy; the association between hearing loss and antiretroviral therapy was significant for subjects aged 35 years or older, but not for subjects younger than 35 years. In subjects aged 35 years or older, this association remained significant using a multivariate model that included those variables found to have the greatest potential for confounding (odds ratio, 4.6; 95% confidence interval, 1.0-20.5; P = .05). CONCLUSIONS: Hearing loss is common among HIV-infected individuals and is associated with antiretroviral therapy in those aged 35 years or older.

Adult↗
PubMed1997

The association of antihypertensive agents with MRI white matter findings and with Modified Mini-Mental State Examination in older adults.

OBJECTIVES: To examine the association of antihypertensive regimen with magnetic resonance imaging (MRI) white matter hyperintensity and with cognitive impairment in older adults. DESIGN: Cross-sectional study. SETTING: The Cardiovascular Health study, an observational prospective cohort study of risk factors for coronary heart disease and stroke in men and women 65 years of age and older. PARTICIPANTS: 1268 men and women with pharmacologically treated hypertension. MEASUREMENTS: Information on medication use, medical history, and health habits was collected at clinic examinations. Participants completed the Modified Mini-Mental State Examination (3MS) and underwent MRI examination. Without clinical information, study neuroradiologists assigned an overall grade of white matter signal intensity on MRI on a scale from 0 (no findings) to 9 (extensive findings). RESULTS: Adjusted mean white matter grade was higher for users of calcium channel blockers (2.59, P = .007) and users of loop diuretics (2.60, P = .015) than for users of beta blockers (2.12). The association was present for both dihydropyridine and non-dihydropyridine calcium channel blockers. Adjusted mean 3MS scores were lower for users of calcium channel blockers (89.6, P < .002), especially dihydropyridines, and users of loop diuretics (89.7, P < .006) than for users of beta blockers (92.3). No statistically significant association could be shown for users of other drug regimens, including thiazides and ACE inhibitors. CONCLUSION: In this study, users of antihypertensive regimens which included calcium channel blockers or loop diuretics had more severe white matter hyperintensity on MRI and worse performance on 3MS than users of beta blockers.

Adrenergic beta-Antagonists↗
PubMed1997

Sulcal, ventricular, and white matter changes at MR imaging in the aging brain: data from the cardiovascular health study.

PURPOSE: To determine the distribution of changes in sulcal size, ventricular size, and white matter signal intensity depicted on cranial magnetic resonance (MR) images, with stratification according to age, race, and sex. MATERIALS AND METHODS: Ventricular size, sulcal size, and white matter signal intensity changes were graded on cranial MR images of 3,660 community-living, elderly participants in the Cardiovascular Health Study. A healthier subgroup was also defined. Summary statistics for both groups were generated for age, race, and sex. RESULTS: Regression models of the entire imaged cohort showed higher grades of all variables with increasing age, and higher ventricular and sulcal grades in men and in nonblack individuals. White matter grade was greater in women and in black individuals. Regression models of the healthier subgroup showed similar associations, except for a lack of association of sulcal and ventricular size with race. CONCLUSION: Sulcal width, ventricular size, and white matter signal intensity change with age, sex, and race. Knowledge of these changes is important in appropriate interpretation of MR images of the elderly.

Aged↗
PubMed1997

Clinically serious abnormalities found incidentally at MR imaging of the brain: data from the Cardiovascular Health Study.

PURPOSE: To determine the prevalence of clinically serious findings unrelated to stroke on cranial magnetic resonance (MR) images in a population of community-dwelling elderly people. MATERIALS AND METHODS: Neuroradiologists reviewed MR images of 3,672 people aged 65 years and older who were enrolled in a longitudinal, population-based study of cardiovascular and cerebrovascular disease. The neuroradiologists alerted MR imaging field centers about potentially serious abnormalities. Clinical information was obtained from clinical examinations performed before MR imaging, hospital discharge summaries, and the field centers at which MR imaging was performed. RESULTS: On 3,672 image sets, 64 (1.74%) clinically serious abnormalities were found. Among the presumptive diagnoses were 19 meningiomas (0.52%), six pituitary adenomas (0.16%), five cavernous malformations (0.14%), eight vascular stenoses (0.22%), four aneurysms (0.11%), two intraventricular masses (0.05%), two subdural fluid collections (0.05%), and two other tumors (0.05%). Only nine participants with these abnormalities required surgery. All but one of the meningiomas were in women, and the prevalence of the tumor decreased with increasing age. CONCLUSION: Physicians should be alert to the possible presence of clinically serious conditions in otherwise asymptomatic elderly individuals.

Aged↗
PubMed1997

Cerebrospinal fluid creatine kinase BB isoenzyme activity and neurologic prognosis after cardiac arrest.

OBJECTIVE: To assess the relationship between CSF creatine kinase BB isoenzyme activity (CSF CKBB) and neurologic outcome after cardiac arrest in clinical practice. BACKGROUND: CSF CKBB reflects the extent of brain damage following cardiac arrest. METHODS: To help with prognosis, treating physicians ordered CSF CKBB tests on 474 patients over 7.5 years; 351 of these patients had experienced a cardiac arrest. Assays were performed in one laboratory using agarose electrophoresis. By chart review, we determined awakening status for all patients, defined as the patient having comprehensible speech or following commands. RESULTS: CSF CKBB was usually sampled 48 to 72 hours after cardiac arrest and was strongly associated with awakening (p < < 0.001). The median was 4 U/l for 61 patients who awakened and 191 U/l for 290 who never awakened. For those who awakened, 75% of CKBB levels were < 24 U/l, and for those who never awakened, 75% were > 86 U/l. The highest value in a patient who awakened was 204 U/l, a cutoff that yielded a specificity of 100% of never awakening but a sensitivity of forty-eight percent. Only nine patients who awakened had CSF CKBB values greater than 50 U/l, and none regained independence in activities of daily living. Only three unconscious patients were still alive at last contact, with follow-up of 63, 107, and 109 months. Using logistic regression, the probability of never awakening given a CSF CKBB result can be estimated as: 1/(1 + L), where L = e raised to (0.1267 - 0.0211 x CSF CKBB [U/l]). CONCLUSION: CSF CKBB measurement helps to estimate degree of brain damage and thus neurologic prognosis after cardiac arrest. However, results of this retrospective study could reflect in part a self-fulfilling prophecy.

Aged↗
PubMed1996

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.

Adult↗
PubMed1996

Plasma thyroid hormone profiles immediately following out-of-hospital cardiac arrest.

Previous studies have shown abnormal thyroid hormone profiles during cardiac arrest. We explored this association further by characterizing plasma thyroid hormone profiles in 473 patients with out-of-hospital cardiac arrest and correlating them with clinical outcomes. Paramedics collected blood at the end of attempted resuscitation regardless of success. Bloods were collected and processed in a similar manner from 18 control subjects randomly selected from the community. Total thyroxine and total triiodothyronine were lower and reverse triiodothyronine and thyrotropin were higher in cardiac arrest patients than control subjects (all p < 0.001). Except for reverse triiodothyronine, findings were similar for a subgroup of cardiac arrest patients considered to be previously healthy (n = 30). Being discharged alive was associated with total thyroxine, total triiodothyronine and reverse triiodothyronine concentrations closer to the control range and thyrotropin concentrations farther from it, namely higher. In a multivariate stepwise model, only total triiodothyronine and thyrotropin were significantly associated with outcome. Whether these profoundly abnormal profiles represent a pre-existing state or a sudden change of thyroid hormone concentrations cannot be answered with this retrospective study. These observations suggest that thyroid hormones may play a role in the etiology of cardiac arrest, its prognosis, or both.

Aged↗
PubMed1996

Clinical correlates of white matter findings on cranial magnetic resonance imaging of 3301 elderly people. The Cardiovascular Health Study.

BACKGROUND AND PURPOSE: Our aim was to identify potential risk factors for and clinical manifestations of white matter findings on cranial MRI in elderly people. METHODS: Medicare eligibility lists were used to obtain a representative sample of 5888 community-dwelling people aged 65 years or older. Correlates of white matter findings were sought among 3301 participants who underwent MRI scanning and denied a history of stroke or transient ischemic attack. Participants underwent extensive standardized evaluations at baseline and on follow-up, including standard questionnaires, physical examination, multiple blood tests, electrocardiogram, pulmonary function tests, carotid sonography, and M-mode echocardiography. Neuroradiologists graded white matter findings from 0 (none) to 9 (maximal) without clinical information. RESULTS: Many potential risk factors were related to the white matter grade, but in the multivariate model the factors significantly (all P < .01) and independently associated with increased grade were greater age, clinically silent stroke on MRI, higher systolic blood pressure, lower forced expiratory volume in 1 second (FEV1), and income less than $50,000 per year. If excluded, FEV1 was replaced in the model by female sex, history of smoking, and history of physician-diagnosed hypertension at the baseline examination. Many clinical features were correlated with the white matter grade, especially those indicating impaired cognitive and lower extremity function. CONCLUSIONS: White matter findings were significantly associated with age, silent stroke, hypertension, FEV1, and income. The white matter findings may not be considered benign because they are associated with impaired cognitive and lower extremity function.

Age Factors↗
PubMed1996

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.

Adult↗
PubMed1996

Neurologic Manifestations of HIV Infection Without AIDS:Follow-UP of a Cohort of Homosexual and Bisexual Men.

To identify neurological abnormalities in HIV infection, 159 HIV-seropositive men without AIDS and 76 seronegative controls underwent standardized general and neurological examinations, lumbar puncture (LP), neuropsychological (NP) assessment, and brain magnetic resonance (MR) imaging. History, physical, and laboratory evaluations were repeated every six months. NP tests (all subjects) and MR imaging (seropositives only) was repeated every 6-12 months; LP (seropositives only) was repeated yearly. Mean follow-up was 24.6 months. Neurological abnormalities, most related to hearing, were seen in 60 (38.2%) of 157 seropositives and 23 (30.3%) of 76 controls at baseline (p = NS). During follow-up, 43 (31.6%) of 136 seropositives had persistent hearing abnormalities compared to 9 (14.1%) of 64 seronegatives (p = 0.008). Seven HIV-seropositives developed peripheral neuropathy; this was more common among those with hearing abnormalities (p = 0.03). HIV-seropositives performed less well on NP tests than controls, but overall performance did not decline. Worsening brain atrophy by MR imaging or cerebrospinal fluid abnormalities are more common in HIV-seropositives than seronegatives and may share a common mechanism with peripheral neuropathy. Further study is needed to determine whether these abnormalities portend more serious neurological disease.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Subarachnoid hemorrhage and family history. A population-based case-control study.

OBJECTIVE: To evaluate family history as a risk factor for subarachnoid hemorrhage. DESIGN AND SETTING: A population-based case-control study in King County, Washington. SUBJECTS: Cases consisted of 149 patients with spontaneous subarachnoid hemorrhage. Two control subjects who were matched to cases by gender and age within 5 years were identified for each case using random digit telephone dialing. MAIN MEASURE: Detailed information on family history was obtained through an in-person interview. RESULTS: Some 11.4% of cases had a first-degree relative with a history of subarachnoid hemorrhage, compared with 6.4% of controls, yielding an odds ratio of 1.8 (95% CI, 0.92 to 3.7). The odds ratio for a positive family history among other relatives was 2.4 (95% CI, 1.1 to 5.2), likely reflecting family information bias. Findings were similar after adjustment was made for potential confounding variables, including cigarette smoking, a history of hypertension, and number of siblings and children. CONCLUSION: Although familial factors may be important in some families, overall they account for few cases of subarachnoid hemorrhage.

Case-Control Studies↗
PubMed1994

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.

Adult↗
PubMed1994

The clinical efficacy of magnetic resonance imaging in neuroimaging.

PURPOSE: To assess the clinical efficacy of magnetic resonance imaging (MRI) for neuroimaging and to provide guidelines for clinical practice. STUDY SELECTION: After a comprehensive literature search, studies of the diagnostic accuracy of MRI alone or compared with other tests and of any impact on therapeutic choices or patient outcomes were reviewed by independent readers, followed by discussion to reach consensus conclusions. DATA EXTRACTION: Of 3125 citations retrieved, 156 studies with original data could be rated according to methodologic criteria for study design. One article contributed grade A quality information about diagnostic accuracy, 28 were graded B or C, and 113 were graded D. One randomized trial and 2 comparison studies contributed grade B or C information about the impact on therapeutic choices. Only 2 studies surveyed health status before and after magnetic resonance scanning. RESULTS: For most abnormalities, the sensitivity of MRI is equal to or better than competing technologies. Magnetic resonance imaging shows greater contrast and detail than computed tomography (CT) but also shows more clinically silent abnormalities or incidental findings. A few studies found a modest impact on therapeutic choices but no impact on quality of life or disability. Costs for MRI are high. Computed tomography is sufficient for initial diagnosis of most mass lesions or intracranial hemorrhages requiring immediate intervention. Magnetic resonance imaging is more accurate in the temporal lobes, posterior fossa, brainstem, and spinal cord. For lumbar radiculopathy, MRI and plain spinal CT are as accurate as post-myelographic CT and are less invasive. The role of magnetic resonance angiography for carotid artery stenosis is being studied. CONCLUSIONS: Although suggestions for appropriate use of MRI in clinical practice can be made, the supporting evidence in published studies is weak. Firm guidelines for appropriate use of MRI should be based on further clinical research using more rigorous methods.

Angiography↗
PubMed1994

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.

Adolescent↗
PubMed1994

Presenting pulse pressure predicts thrombolytic therapy-related intracranial hemorrhage. Thrombolytic Predictive Instrument (TPI) Project results.

BACKGROUND: In selecting patients with acute myocardial infarction for thrombolytic therapy, it is important to identify patients who are at high risk for intracranial hemorrhage, for whom thrombolytic therapy is ill advised. We hypothesized that presenting pulse blood pressure, representing the "hammer" effect on cerebral vessels and the effects of age on arterial compliance, might predict thrombolysis-related intracranial hemorrhage better than systolic, diastolic, or mean arterial blood pressures. METHODS AND RESULTS: Of 3483 Thrombolytic Predictive Instrument (TPI) Project subjects receiving thrombolytic therapy for acute infarction, we identified and obtained detailed clinical data on the 19 with treatment-related intracranial hemorrhages confirmed by computed tomography and on 175 matched controls. Systolic, diastolic, mean arterial, and pulse blood pressures were each significantly related to the occurrence of intracranial hemorrhage, with pulse pressure most highly related. The mean pulse pressure in patients who developed intracranial hemorrhage was 63 mm Hg, 34% higher than the 47 mm Hg mean value for those not developing hemorrhage (P = .0001). Excess pulse pressure, defined as the extent to which a patient's pulse pressure exceeded 40 mm Hg for systolic blood pressures of at least 120 mm Hg, was even more strongly related: its mean value of 23 mm Hg for patients was 130% higher than its mean value of 10 mm Hg for controls (P < .0001). With logistic regression models to estimate the relative risks (odds ratios) for intracranial hemorrhage conferred by each form of blood pressure, the relative risk for hemorrhage was greatest for excess pulse pressure: for each 10-point pulse pressure excess, the relative risk for intracranial hemorrhage was increased by 1.85 (P = .0002; 95% confidence interval [CI], 1.34 to 2.55) by itself and 1.76 (P = .001; 95% CI, 1.26 to 2.46) when adjusted for age. In this sample, excess pulse pressure by itself predicted hemorrhage as well as systolic pressure and age together. When excess pulse pressure was combined with age to make a logistic regression model predicting intracranial hemorrhage, age contributed less to the prediction than when combined with the other blood pressure forms, even though this model predicted better than any other combination of age and pressure (receiver-operating characteristic curve area, 0.82 versus 0.77 with systolic pressure and age, 0.75 with mean arterial pressure, 0.71 with diastolic pressure, and 0.81 with both systolic and diastolic pressures). CONCLUSIONS: We found that excess pulse blood pressure predicted thrombolysis-related intracranial hemorrhage better than other forms of pretreatment blood pressure, perhaps better describing the pathophysiology of intracranial hemorrhage, including the effect of age. These findings will need confirmation in larger studies with comparable clinical detail.

Aged↗