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Biomedical subjects

T A Stukel

Publications and source records attributed to T A Stukel.

At least 19 recordsLinked to original sources
PubMed1998

Brain size, head size, and intelligence quotient in monozygotic twins.

Many studies of monozygotic (MZ) twins have revealed evidence of genetic influences on intellectual functions and their derangement in certain neurologic and psychiatric diseases afflicting the forebrain. Relatively little is known about genetic influences on the size and shape of the human forebrain and its gross morphologic subdivisions. Using MRI and quantitative image analysis techniques, we examined neuroanatomic similarities in MZ twins and their relationship to head size and intelligence quotient (IQ). ANOVA were carried out using each measure as the dependent variable and genotype, birth order, and sex, separately, as between-subject factors. Pairwise correlations between measures were also computed. We found significant effects of genotype but not birth order for the following neuroanatomic measures: forebrain volume (raw, p < or = 0.0001; normalized by body weight, p = 0.0003); cortical surface area (raw, p = 0.002; normalized, p = 0.001); and callosal area (raw, p < or = 0.0001; normalized by forebrain volume, p = 0.02). We also found significant effects of genotype but not birth order for head circumference (raw, p = 0.0002; normalized, p < or = 0.0001) and full-scale IQ (p = 0.001). There were no significant sex effects except for raw head circumference (p = 0.03). Significant correlations were observed among forebrain volume, cortical surface area, and callosal area and between each brain measure and head circumference. There was no significant correlation between IQ and any brain measure or head circumference. These results indicate that: 1) forebrain volume, cortical surface area, and callosal area are similar in MZ twins; and 2) these brain measures are tightly correlated with one another and with head circumference but not with IQ in young, healthy adults.

Adult↗
PubMed1998

Trends in pediatric asthma hospitalization rates: regional and socioeconomic differences.

OBJECTIVE: Asthma hospitalization rates continue to increase nationally for children despite efforts by the National Institutes of Health and specialty organizations to improve outcomes through the dissemination of practice guidelines. To understand the generalizability of national trends to regional populations, we studied childhood hospitalizations over a 10-year period in four northeastern states. DESIGN: Longitudinal analysis of hospitalization rates by patient residence and patient characteristics using state hospital discharge datasets. POPULATION: Age < 18 years residing in Maine, New Hampshire, Vermont, or New York state during the period 1985 to 1994. RESULTS: In multivariate analyses (controlling for age, sex, race/ethnicity, median household income, metropolitan status), we found that New York asthma hospitalization rates increased 3.8% per annum (95% confidence interval: 3.3, 4.2), whereas in New Hampshire, rates decreased 5.8% (95% confidence interval: 7.6, 4.1). Maine and Vermont rates did not change significantly during the study period. Increased asthma hospitalization rates were noted in black and Hispanic populations, in children residing in zip codes with lower median household incomes, and in those living in metropolitan areas. Hospitalization rates for nonasthma causes fell substantially. As a result, the proportion of hospital days attributed to childhood asthma increased in all population groups. CONCLUSIONS: Asthma discharge rates measured by the state of residence or socioeconomic characteristic do not necessarily parallel national trends. None of the current hypotheses offered to explain national trends in asthma hospitalization rates (changes in disease severity, diagnostic substitution, or differences in the supply and character of medical care) can be the sole explanation of these regional trends. Efforts intended to improve asthma outcomes may benefit a greater number of children by redirecting resources toward specific populations identified through state hospital discharge datasets.

Adolescent↗
PubMed1997

A comparison of clomiphene citrate and human menopausal gonadotropin for use in conjunction with intrauterine insemination.

OBJECTIVE: To compare the outcome of superovulation using clomiphene citrate (CC) versus hMG in conjunction with IUI. DESIGN: Sequentially assigned, observational study. Couples initially were assigned to receive either CC or hMG for three cycles. SETTING: The Clinical Outpatient Department of the Dartmouth-Hitchcock Medical Center. PATIENT(S): Eighty-three infertile couples. INTERVENTION(S): IUI with hMG use. MAIN OUTCOME MEASURE(S): Conception rate, term pregnancy rate (PR), and pregnancy complications, such as spontaneous miscarriage and multiple gestation. RESULT(S): Of 83 couples who underwent at least one treatment cycle, 29 (35%) conceived during the study period. The relative rate of conception for hMG versus CC was 2.08 (95% confidence interval [CI], 0.93 to 4.68). The relative term PR was 2.10 (95% CI, 0.77 to 5.73) for hMG versus CC. There was no difference in the miscarriage rate for hMG versus CC. CONCLUSION(S): Both the conception rate and the term PR were higher using hMG, compared with CC, in combination with IUI, and showed a trend toward statistical significance.

Adult↗
PubMed1997

Superficial femoral artery stenoses: characteristics of progressing lesions.

PURPOSE: The purpose of this study was to assess the effect of superficial femoral artery (SFA) stenosis morphologic characteristics and lesion location on the rate of atherosclerotic disease progression. METHODS: We identified 19 patients who required arteriography for treatment of critical leg ischemia and who had previously undergone arteriography of that leg when minimal or no symptoms were present. These initial incidental arteriographic evaluations were performed during evaluation of arterial disease in another vascular bed from 4 to 81 months (mean, 32 months) previously. Distinct SFA stenoses or occlusion on the final arteriogram (n = 98) were characterized by their location, length, stenosis severity, and morphologic appearance on the initial arteriogram. The contribution of patient-specific risk factors to disease progression was also assessed. RESULTS: Stenosis progression occurred independently among multiple lesions within the same patient (negligible intraclass correlation coefficient, r = 0.06). Lesions in the adductor canal region were more likely to occlude than lesions elsewhere in the SFA (adjusted odds ratio = 10.7; p = 0.03). Severity of initial lesion stenosis also was predictive of occlusion (adjusted odds ratio = 1.8; p = 0.04). However, most progressing lesions (93%) actually arose in areas of initially mild disease (stenoses < 50%) despite more severe initial lesions elsewhere. Increasing age (p = 0.023) and previous contralateral leg bypass (p = 0.036) were also associated with increasing rates of lesion progression. Smooth-asymmetric lesions progressed 11% more slowly than other lesion types (p = 0.003). CONCLUSIONS: Our analysis of atherosclerotic SFA lesion progression in patients with critical ischemia shows that initial stenosis severity was associated with higher occlusion rates and that smooth-asymmetric lesions progressed more slowly than lesions with other morphologic characteristics. Severe stenoses usually arose from minimally diseased regions and progressed more rapidly than preexisting, more highly stenotic lesions. Most SFA occlusions resulted from disease progression in the adductor canal region whether or not antecedent lesions were seen on arteriography and whether or not more severe stenoses were initially present elsewhere. Increased age and history of previous contralateral bypass were patient-specific predictors of lesion progression.

Aged↗
PubMed1997

Effects of anesthetic technique on myocardial wall motion abnormalities during abdominal aortic surgery.

OBJECTIVE: To assess the impact of regional supplemented general anesthesia (RSGEN) on regional myocardial function during abdominal aortic surgery (AAS). DESIGN: Prospective randomized study. SETTING: Single academic medical center. PARTICIPANTS: Seventy-three patients scheduled for infrarenal aortic aneursymectomy. INTERVENTIONS: Patients received standardized intraoperative anesthetic management consisting of either general anesthesia (GA; n = 37) or general anesthesia supplemented by epidural anesthesia (RSGEN; n = 36). MEASUREMENTS AND MAIN RESULTS: Hemodynamic measurements and transesophageal echocardiograms (TEE) were obtained at eight intraoperative times. The electrocardiogram (ECG) was continuously recorded using Holter monitoring. Of the 56 patients with interpretable TEE recordings, 8 of 30 (27%) GA patients and 7 of 26 (27%) RSGEN patients developed new segmental wall motion abnormalities (SWMAs). There was no treatment effect on either the incidence (p = 0.23) or the intensity (p = 0.34) of SWMAs. Cross-clamping of the aorta was associated with the onset of new SWMAs (odds ratio, 8.2; 95% CI, 1.1 to 64; p = 0.04). Among the 63 patients with interpretable Holter recordings, 9 of 34 (26%) GA patients and 9 of 29 (31%) RSGEN patients exhibited intraoperative ischemia. There was no treatment effect on the incidence (p = 0.22) or intensity (p = 0.67) of ECG ischemia. CONCLUSION: Despite providing modest hemodynamic depression, RSGEN did not reduce the incidence or intensity of either regional myocardial dysfunction or ECG ischemia. New SWMAs were temporally associated with cross-clamping of the aorta and tended to resolve with unclamping.

Aged↗
PubMed1997

The distance to community medical care and the likelihood of hospitalization: is closer always better?

OBJECTIVES: This study examined the influence that distance from residence to the nearest hospital had on the likelihood of hospitalization and mortality. METHODS: Hospitalizations were studied for Maine. New Hampshire, and Vermont during 1989 (adults) and for 1985 through 1989 (children) and for mortality (1989) in Medicare enrollees. RESULTS: After other known predictors of hospitalization (age, sex, bed supply, median household income, rural residence, academic medical center, and presence of nursing home patients) were controlled for, the adjusted rate ratio of medical hospitalization for residents living more than 30 minutes away was 0.85 (95% confidence interval [CI] = 0.82, 0.88) for adults and 0.78 (95% CI = 0.74, 0.81) for children, compared with those living in a zip code with a hospital. Similar effects were seen for the four most common diagnosis-related groups for both adults and children. The likelihood of hospitalization for conditions usually requiring hospitalization and for mortality in the elderly did not differ by distance. CONCLUSIONS: Distance to the hospital exerts an important influence on hospitalization rates that is unlikely to be explained by illness rates.

Adolescent↗
PubMed1997

Risk of squamous cell carcinoma of the skin in relation to plasma selenium, alpha-tocopherol, beta-carotene, and retinol: a nested case-control study.

We conducted a nested case-control study of squamous cell skin cancer (SCC) to determine whether risk was related to plasma concentrations of selenium, alpha-tocopherol, beta-carotene, and retinol. We derived the study sample from participants in our Skin Cancer Prevention Study, all of whom had at least one basal cell or squamous cell skin cancer before study entry. Those who developed a new squamous cell skin cancer during the 3-5-year follow-up period were selected as cases (n = 132). Controls (n = 264) were chosen at random, with matching by age, sex, and study center, from among those who did not develop SCC but were being followed actively at the time the SCC case was diagnosed. Prediagnostic plasma samples were analyzed for alpha-tocopherol, beta-carotene, and retinol using high-performance liquid chromatography. Selenium determinations were made using instrumental neutron activation analysis. Odds ratios were computed using conditional logistic regression for matched samples. We found no consistent pattern of SCC risk associated with any of the nutrients examined. The odds ratios (95% confidence intervals) for the highest versus the lowest quartiles of beta-carotene, retinol, alpha-tocopherol, and selenium were 0.73 (0.38-1.41), 1.43 (0.77-2.64), 0.89 (0.43-1.85), and 0.86 (0.47-1.58), respectively. Thus, our data add to the growing body of evidence that these nutrients, at the concentrations we evaluated, are not related strongly to SCC risk.

Adult↗
PubMed1997

Two-stage method of estimation for general linear growth curve models.

We extend the linear random-effects growth curve model (REGCM) (Laird and Ware, 1982, Biometrics 38, 963-974) to study the effects of population covariates on one or more characteristics of the growth curve when the characteristics are expressed as linear combinations of the growth curve parameters. This definition includes the actual growth curve parameters (the usual model) or any subset of these parameters. Such an analysis would be cumbersome using standard growth curve methods because it would require reparameterization of the original growth curve. We implement a two-stage method of estimation based on the two-stage growth curve model used to describe the response. The resulting generalized least squares (GLS) estimator for the population parameters is consistent, asymptotically efficient, and multivariate normal when the number of individuals is large. It is also robust to model misspecification in terms of bias and efficiency of the parameter estimates compared to maximum likelihood with the usual REGCM. We apply the method to a study of factors affecting the growth rate of salmonellae in a cubic growth model, a characteristic that cannot be analyzed easily using standard techniques.

Animals↗
PubMed1996

Risk of basal cell and squamous cell skin cancers after ionizing radiation therapy. For The Skin Cancer Prevention Study Group.

BACKGROUND: Human evidence that ionizing radiation is carcinogenic first came from reports of nonmelanoma skin cancers (NMSCs) on the hands of workers using early radiation devices. An increased risk of NMSC has been observed among uranium miners, radiologists, and individuals treated with x rays in childhood for tinea capitis (ringworm of the scalp) or for thymic enlargement; NMSC is one of the cancers most strongly associated with the atomic bombing of Hiroshima and Nagasaki. Although exposure to ionizing radiation is a known cause of NMSC, it is not yet clear whether therapeutic radiation causes both major histologic types of NMSC, basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). Additionally, the potentially modifying effects, such as latency, age when treated, and type of treatment, are not well understood. PURPOSE: We investigated the relative risks of BCC and SCC associated with previous radiation therapy and evaluated these risks in relation to age and time since initial treatment and the medical condition for which radiation therapy was given. METHODS: The study group comprised individual diagnosed with at least one BCC or SCC from January 1980 through February 1986, who were recruited to participate in a skin cancer prevention trial designed to test whether oral beta-carotene supplementation would reduce the risk of new NMSCs. Patients were identified through the dermatology and pathology records of academic medical centers in Hanover, NH; Los Angeles, CA; San Francisco, CA; and Minneapolis, MN. Each participant completed a questionnaire detailing lifetime residence, pigmentary characteristics, occupational and recreational sun exposure, and history of radiation therapy. At enrollment, a study dermatologist assessed skin type (tendency to burn or tan) and extent of actinic skin damage. Participants were followed with an annual dermatologic examination for an average of 4 years. Of the 5232 potentially eligible individuals, 1805 were enrolled in the trial. We excluded 112 patients who reported previous radiation therapy for skin cancer only and three with missing information on whether they were ever treated with radiation therapy, leaving 1690 patients for the analysis. Approximately 4% of the patients died or discontinued participation for other reasons during each study year. We examined time to occurrence of first new histopathologically confirmed BCC and SCC during the follow-up period in relation to history of radiation therapy (for reasons other than NMSC) using a proportional hazards model. A multiple end points survival model was used to compare the rate ratios (RRs) for BCC and SCC. We also used a longitudinal method of analysis to compute the RR of total new BCC and SCC tumors per person per study year associated with radiation therapy. Using this method, we additionally assessed the potential modifying effects of age at treatment, latency, and type of therapy. All P values were derived from two-sided statistical tests of significance. RESULTS: Among the participants we studied, 597 developed a new BCC (n = 1553 tumors) and 118 developed a new SCC (n = 179 tumors). The time to first new BCC, but not SCC, was associated with prior radiation therapy (RR = 1.7; 95% confidence interval [CI] = 1.4-2.0 and RR = 1.0; 95% CI = 0.6-1.7, respectively; P = .03 for the difference between the RRs). The RR of total BCC tumors was slightly higher (RR = 2.3; 95% CI = 1.7-3.1), but it was still unity for SCC (RR = 1.0; 95% CI = 0.5-1.9). BCC risk appeared to increase with younger age at exposure and time since initially treated, although these effects were only marginally statistically significant (P for trend = .06 and .07, respectively). Also, risk of BCC was more strongly related to treatment for acne (RR = 3.3; 95% CI = 2.1-5.2) than other conditions. CONCLUSIONS AND IMPLICATIONS: Our data suggest that exposure to therapeutic radiation is associated with BCC but not with SCC.

Adult↗
PubMed1996

Mortality associated with low plasma concentration of beta carotene and the effect of oral supplementation.

OBJECTIVE: To examine the relationship between beta carotene plasma concentration and beta carotene supplementation and risk of death from major disease causes. DESIGN: Cohort study of plasma concentrations; randomized, controlled clinical trial of supplementation. SETTING: Medical school-affiliated dermatology practices. PATIENTS: A total of 1188 men and 532 women with mean age of 63.2 years, who had enrolled in a randomized clinical trial of beta carotene supplementation to prevent nonmelanoma skin cancer. INTERVENTION: Oral beta carotene, 50 mg per day for a median of 4.3 years. MAIN OUTCOME MEASURES: All-cause mortality and mortality from cardiovascular disease and cancer. RESULTS: During a median follow-up period of 8.2 years, there were 285 deaths. Persons whose initial plasma beta carotene concentrations were in the highest quartile (>0.52 micromol/L [27.7 microg/dL]) had a lower risk of death from all causes (adjusted relative rate [RR], 0.52; 95% confidence interval [CI] 0.44 to 0.87) and from cardiovascular diseases (adjusted RR, 0.57; 95% CI, 0.34 to 0.95) compared with persons with initial concentrations in the lowest quartile (<0.21 micromol/L [11.2 microg/dL]). Patients randomly assigned to beta carotene supplementation showed no reduction in relative mortality rates from all causes (adjusted RR, 1.03; 95% CI, 0.82 to 1.30) or from cardiovascular disease (adjusted RR, 1.16; 95% CI, 0.82 to 1.64). There was no evidence of lower mortality following supplementation among patients with initial beta carotene concentrations below the median for the study group. CONCLUSIONS: These analyses provide no support for a strong effect of supplemental beta carotene in reducing mortality from cardiovascular disease or other causes. Although the possibility exists that beta carotene supplementation produces benefits that are too small or too delayed to have been detected in this study, noncausal explanations should be sought for the association between plasma concentrations of beta carotene and diminished risk of death.

Administration, Oral↗
PubMed1996

Utility of a risk assessment questionnaire in identifying children with lead exposure.

OBJECTIVE: To evaluate the utility of the Centers for Disease Control and Prevention (CDC) Risk Questionnaire and a behavioral risk factor questionnaire in identifying children with blood lead concentrations of 0.48 mumol/L (10 micrograms/dL) or more. DESIGN: Cross-sectional study of 463 urban Massachusetts children (6 to 72 months of age) screened for lead with venous blood. RESULTS: Twenty-two percent of the children had elevated blood lead concentrations. Of the five CDC questions, only one was significantly associated with an increased adjusted odds ratio for elevated blood lead: having a sibling, housemate, or playmate who was followed up or treated for lead poisoning (odds ratio, 2.7; 95% confidence interval, 1.7 to 4.2; P < .001). Children who had at least one positive or equivocal response to any of the five CDC questions (n = 318 [68.7%]) were not at higher risk than were children who displayed a negative response to all five questions (odds ratio, 1.1; 95% confidence interval, 0.7 to 1.8; P = .69). Of nine behaviors surveyed, two were associated with an increased adjusted odds for elevated blood lead: use of a pacifier (odds ratio, 2.4; 95% confidence interval, 1.3 to 4.4; P = .01) and playing near the outside of the home (odds ratio, 3.4; 95% confidence interval, 2.0 to 5.8; P < .001). CONCLUSIONS: In this population of children, the CDC risk questionnaire did not identify a group at higher risk for lead exposure. We suggest that practitioners in urban communities screen all children according to the same schedule. We conclude that risk factors differ by community and no risk questionnaire developed at the national level should be applied across communities to target screening.

Centers for Disease Control and Prevention, U.S.↗
PubMed1996

Iron deficiency in Massachusetts communities: Socioeconomic and demographic risk factors among children.

OBJECTIVES: This study examined the association between community rates of iron deficiency in children and sociodemographic characteristics of Massachusetts communities. METHODS: Between April 1990 and March 1991, 238 273 Mssachusetts children 6 through 59 months of age were screened; iron deficiency was defined as an erythrocyte protopophyrin concentration of 0.62 micromol/L or higher and a blood lead level of less than 1.2 micromol/L. Sociodemographic data were obtained from the 1990 US Census. RESULTS: Five percent of communities had iron deficiency rates greater than 13.9 per 100 children screened. Iron deficiency rate was positively associated with proportion of Southeast Asians (odds ratio [OR] = 1.10, 95% confidence interval [CI] = 1.08, 1.12), proportion of Hispanics (OR = 1.008, 95% CI = 1.002, 1.013), and high school incompletion (OR = 1.028, 95% CI = 1.020, 1.035). Similarly, an examination of three Massachusetts cities indicated that the iron deficiency rate was higher for children with Southeast Asian (relative risk [RR] = 3.6, 95% CI = 3.3, 3.8) and Hispanic (RR = 1.6, 95% CI = 1.5, 1.8) surnames than for all other children. CONCLUSIONS: Wide variation exists in iron deficiency rates for children in Massachusetts communities. Community iron deficiency was associated with low socioeconomic status and high proportions of Southeast Asians and Hispanics.

Anemia, Iron-Deficiency↗
PubMed1995

Long-term morbidity following jejunoileal bypass. The continuing potential need for surgical reversal.

OBJECTIVE: To review the late sequelae of jejunoileal bypass (JIB) and the potential role of late surgical reversal in ameliorating morbidity and mortality following JIB. DESIGN: Patients who underwent JIB between 1965 and 1977 were contacted and pertinent health-event information was gathered. Early sequelae were defined as disorders occurring within the first 2 years after JIB; late sequelae were those occurring after 2 years. Health events occurring between 0 and 23 years after JIB were documented. SETTING: A private, tertiary referral center. PATIENTS: Patients underwent JIB for morbid obesity that had failed medical and/or psychiatric interventions. MAIN OUTCOME MEASURES: Body mass index (BMI) (weight kilograms divided by the square of the height in meters), diarrhea, electrolyte imbalance, acute, and chronic liver disease, renal disease, JIB reversal, reason for JIB reversal, death, and cause of death. RESULTS: A total of 453 morbidity obese patients underwent JIB. By 2 years following JIB, the mean (+/- SD) BMI dropped from 49.3 +/- 8.1 to 31.1 +/- 0.8 and remained at this level until year 15, after which weight gradually increased (BMI, 35.4 +/- 3.1). The most severe early complication was acute liver failure, which occurred in 7% of patients and caused seven deaths. At 15 years, the actuarial probability of the most common serious late complications related to JIB were renal disease (37%), with two deaths; diarrhea (29%); and liver disease (10%), with three deaths. One hundred thirty-eight patients (31%) had a bypass reversal. The most common indications for reversal were diarrhea and electrolyte disturbance (29%), renal disease (19%), and liver disease (17%). Fifty-six patients died more than 30 days after JIB: 64% before JIB reversal, 13% at the time of reversal, and 23% subsequently. CONCLUSIONS: Jejunoileal bypass is associated with progressive accrual of serious, sometimes life-threatening complications. Lifelong follow-up for early diagnosis and surgical reversal before life is threatened should reduce the morbidity and mortality associated with this procedure.

Acid-Base Imbalance↗
PubMed1994

Hospital readmission rates for cohorts of Medicare beneficiaries in Boston and New Haven.

BACKGROUND: Geographic variations in the use of hospital services are associated with differences in the availability of hospital beds. There continues to be uncertainty about the extent to which unmeasured case-mix differences explain these findings. Previous research showed that the number of occupied beds per capita in Boston was substantially higher than the number of occupied beds per capita in New Haven, Connecticut, and that overall rates of hospital utilization were higher for Boston residents than for New Haven residents. METHODS: We used Medicare claims data to study cohorts of Medicare beneficiaries 65 years of age or older and residing in Boston or New Haven who were initially hospitalized for one of five indications (acute myocardial infarction, stroke, gastrointestinal bleeding, hip fracture, or potentially curative surgery for breast, colon, or lung cancer). Residents of Boston or New Haven who were discharged between October 1, 1987, and September 30, 1989, were enrolled in the cohort corresponding to the earliest such admission and followed for up to 35 months. RESULTS: The relative rate of readmission in Boston as compared with New Haven was 1.64 (95 percent confidence interval, 1.53 to 1.76) for all cohorts combined, with a similarly elevated rate for each of the five clinical cohorts and each age, sex, and race subgroup examined. Hospital-specific readmission rates varied substantially among the hospitals in Boston and were higher than those in New Haven. No relation was found between mortality (during the first 30 days after discharge or over the entire study period) and either community or hospital-specific readmission rates. CONCLUSIONS: Regardless of the initial cause of the admission, Medicare beneficiaries who were initially hospitalized in Boston had consistently higher rates of readmission than did Medicare beneficiaries hospitalized in New Haven. Differences in the severity of illness are unlikely to explain these findings. One possible explanation is a threshold effect of hospital-bed availability on decisions to admit patients.

Aged↗
PubMed1994

Standardized rates of recurrent outcomes.

Longitudinal studies are often concerned with estimating the rate of an event that may recur. Examples are nonmelanoma skin cancer rates, screening rates for breast cancer using mammography and hospital admission rates. We propose simple estimators for directly and indirectly standardized summary rates and relative rates of recurrent events and their variances. We also develop an estimator of the excess rate in an area if the rate in another area applied. For non-recurrent events, the estimators are identical to the usual standardized summary rates. The estimators are independent of the underlying distribution of the event of interest and allow for unequal follow-up times and event rate heterogeneity among individuals. The method is not computationally intensive and does not require specialized software. We illustrate the application of the method in a retrospective cohort study of hospital utilization patterns of Medicare enrollees in Boston and New Haven over a three and a half year period.

Boston↗
PubMed1994

Steady-state serum concentration of alpha tocopherol not altered by supplementation with oral beta carotene. The Polyp Prevention Study 1 Group.

BACKGROUND: The antioxidants beta carotene and vitamin E may play a role in cancer prevention. However, some studies have suggested that oral supplements of beta carotene may cause a decrease in serum levels of alpha tocopherol (vitamin E). PURPOSE: We conducted this study to determine if beta carotene supplements affect serum levels of vitamin E and vice versa. METHODS: Five hundred five patients in a clinical trial of antioxidant vitamins, used to prevent recurrences of colonic polyps, received either a placebo, 25 mg of beta carotene per day, 1 g ascorbic acid plus 400 mg alpha tocopherol per day, or all three agents combined. Serum levels of beta carotene and vitamin E were measured before and after 9 months of supplementation, using high-performance liquid chromatography. RESULTS: Vitamin E levels changed very little among the groups receiving placebo or beta carotene and went up substantially and equally in the groups receiving vitamin E plus ascorbic acid or all three agents together. Conversely, beta carotene levels changed very little for the groups receiving placebo or ascorbic acid plus vitamin E but went up substantially and equally for the groups receiving beta carotene alone or all three agents. CONCLUSIONS: We conclude that oral supplementation with beta carotene for 9 months does not alter serum concentration of vitamin E and that supplementation with vitamin E plus ascorbic acid does not alter serum beta carotene levels.

Administration, Oral↗