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S D Halpern

Publications and source records attributed to S D Halpern.

11 recordsLinked to original sources
PubMed2001

Who will enroll? Predicting participation in a phase II AIDS vaccine trial.

BACKGROUND: The problems of underenrollment and selective enrollment may undermine AIDS vaccine trials. If prospective study subjects' stated willingness to participate (WTP) in hypothetical vaccine trials predicts future enrollment, then measuring WTP before recruitment may enhance the enrollment in, and ethics of, such trials. METHODS: We prospectively studied changes over an 18-month period in the stated WTP in, and knowledge of, a hypothetical AIDS vaccine trial among 610 Philadelphia residents at high risk for HIV infection. Of these people, 499 were subsequently recruited to participate in an actual, phase II AIDS vaccine trial. We used multivariable logistic regression and the area under the receiver-operating characteristic (ROC) curve to model predictors of actual enrollment. RESULTS: Actual enrollment rates were 8.3%, 6.8%, 15.8%, and 29.0% among those who had initially said they were "definitely not," "probably not," "probably," and "definitely" willing to participate, respectively (p =.006). The area under the ROC curve was 0.65, indicating a modest ability of stated WTP to differentiate those who enroll from those who do not. Knowledge of basic vaccine trial concepts, though unrelated to enrollment, increased over an 18-month period with repeated education sessions (p <.0001), whereas stated WTP declined over this same period (p <.0001). CONCLUSION: Although other factors not captured by stated WTP may also influence future enrollment, prospectively assessing stated WTP may augment the validity of the informed consent process, help prevent underenrollment, and clarify the population from which the study sample is drawn.

AIDS Vaccines↗
PubMed2001

Declining rate of substance abuse throughout the month.

PURPOSE: The timing of federal disbursements of welfare, disability, and military benefits may be associated with monthly patterns of substance abuse. We assessed whether this association was reflected in the pattern of psychiatric presentations to an emergency room. SUBJECTS AND METHODS: We conducted a retrospective, case-control study of 12,904 patient presentations to an urban emergency department for psychiatric reasons during a 7-year period. Cases were defined as patients (n = 2,403) given a primary diagnosis of substance abuse. Controls included patients (n = 10,501) with a primary diagnosis of another psychiatric illness. We calculated the "boundary effect" (R = 100 times the number of presentations during the first week of the month divided by number of presentations during the last week of the preceding month) for each month, and averaged these values across months to determine overall effects. RESULTS: The boundary effect was stronger for patients with primary substance abuse disorders (R = 134, 95% confidence interval [CI] = 118 to 151) than for patients with other psychiatric disorders (R = 106, 95% CI = 100 to 112; P < 0.001). Weekly presentations for substance abuse declined consistently throughout the month (P = 0.01), and declined significantly more than the incidence of other psychiatric presentations (P = 0.005). These effects remained, after adjusting for fluctuations in presentations around holidays and the new year. The lunar cycle did not influence the incidence of presentations. CONCLUSION: Our results confirm that substance-related morbidity is highest at the beginning of the month and declines thereafter, corresponding to the availability of disposable income from monthly checks.

Adult↗
PubMed1999

Interindividual variation in human visual performance.

The responses of 20 young adult emmetropes with normal color vision were measured on a battery of visual performance tasks. Using previously documented tests of known reliability, we evaluated orientation discrimination, contrast sensitivity, wavelength sensitivity, vernier acuity, direction-of-motion detection, velocity discrimination, and complex form identification. Performance varied markedly between individuals, both on a given test and when the scores from all tests were combined to give an overall indication of visual performance. Moreover, individual performances on tests of contrast sensitivity, orientation discrimination, wavelength discrimination, and vernier acuity covaried, such that proficiency on one test predicted proficiency on the others. These results indicate a wide range of visual abilities among normal subjects and provide the basis for an overall index of visual proficiency that can be used to determine whether the surprisingly large and coordinated size differences of the components of the human visual system (Andrews, Halpern, & Purves, 1997) are reflected in corresponding variations in visual performance.

Adult↗
PubMed1997

Correlated size variations in human visual cortex, lateral geniculate nucleus, and optic tract.

We have examined several components of the human visual system to determine how the dimensions of the optic tract, lateral geniculate nucleus (LGN), and primary visual cortex (V1) vary within the same brain. Measurements were made of the cross-sectional area of the optic tract, the volumes of the magnocellular and parvocellular layers of the LGN, and the surface area and volume of V1 in one or both cerebral hemispheres of 15 neurologically normal human brains obtained at autopsy. Consistent with previous observations, there was a two- to threefold variation in the size of each of these visual components among the individuals studied. Importantly, this variation was coordinated within the visual system of any one individual. That is, a relatively large V1 was associated with a commensurately large LGN and optic tract, whereas a relatively small V1 was associated with a commensurately smaller LGN and optic tract. This relationship among the components of the human visual system indicates that the development of its different parts is interdependent. Such coordinated variation should generate substantial differences in visual ability among humans.

Adult↗
PubMed1994

Emergency department patterns in psychiatric visits during the holiday season.

STUDY OBJECTIVE: To determine the prevalence of psychopathology during the holiday season and which subpopulations are at greatest risk for holiday decompensation. DESIGN: A retrospective analysis of emergency department records. SETTING: ED of a university-affiliated hospital located in a mixed urban-agricultural catchment area in North Carolina. PARTICIPANTS: Eight thousand seven hundred fifty-six patient visits to the ED, with subsequent triage for psychiatric evaluation, for a 6-year period (1987 to 1993), were analyzed. RESULTS: We observed seasonal patterns in visits, with a general decrease in visits preceding holidays followed by an increase afterward. Substance abusers, men, and black patients were more likely to visit the ED than expected, particularly during the weeks surrounding Christmas. CONCLUSION: These results support the existence of a "Christmas effect" on ED visitations by patients with psychiatric symptoms. Understanding of these patterns may help emergency physicians predict the seasonal variation of such patient visits and apply preventive measures accordingly.

Emergency Service, Hospital↗
PubMed1978

A comparison of intralingual and intravenous epinephrine before and during cardiovascular depression.

Dose-response methodology was used to evaluate the cardiopulmonary effects of epinephrine administered intravenously and intralingually to normotensive and acutely hypotensive dogs and monkeys. Results indicate that the intralingual route is much less effective than the intravenous route and that conventional doses of emergency drugs injected intralingually may not afford sufficient resuscitative effects to be lifesaving during cardiovascular depression.

Acute Disease↗