Biomedical subjects

S Lipsitz

Publications and source records attributed to S Lipsitz.

24 records · Page 2Linked to original sources

PubMed1994

Dietary vitamin A intake and the risk of mortality among children.

Increased consumption of dietary vitamin A is advocated as a long-term solution to vitamin A deficiency. We prospectively examined the relationship of dietary vitamin A intake and child mortality among 28,753 Sudanese children aged 6 mo to 6 y, who participated in a trial of vitamin A supplementation. After 18 mo of follow-up, 232 children died. Total dietary vitamin A intake was strongly and inversely associated with risk of mortality. The age- and sex-adjusted relative risk (RR) of mortality for a comparison of children in extreme quintiles was 0.35 (95% CIs 0.21-0.60; P for trend over quintiles < 0.0001). Even after possible confounding by socioeconomic variables was adjusted for, vitamin A intake was significantly protective (multi-variate relative risk 0.53). Dietary vitamin A intake was especially protective among children who were wasted and stunted or who had diarrhea or cough. These prospective data support an important role of dietary vitamin A in reducing childhood mortality in developing countries.

Age Factors↗

PubMed1993

Vitamin A supplementation and dietary vitamin A in relation to the risk of xerophthalmia.

We examined the effect of 60-mg (200,000-IU) supplements of vitamin A administered every 6 mo on the incidence of xerophthalmia among preschool children who were free of eye symptoms and signs of vitamin A deficiency. We also prospectively studied the relationship of dietary vitamin A intake with the same endpoint. After 18 mo of follow-up, 400 children developed xerophthalmia during 80,104 child-periods of follow-up. Vitamin A supplementation only modestly reduced the risk of xerophthalmia (relative risk 0.88, 95% confidence interval 0.72-1.07, P = 0.19). On the other hand, total dietary vitamin A intake was strongly associated with reduced risk of xerophthalmia; the multivariate relative risk when children in extreme quintiles were compared was 0.38 (95% confidence interval 0.19-0.74; P for trend over quintiles = 0.002). These results emphasize the need for further data on factors that modify the bioavailability of large-dose vitamin A supplements. Increased consumption of inexpensive vegetables and fruits is highly likely to reduce significantly the risks of vitamin A deficiency, including nutritional blindness in developing countries.

Child↗

PubMed1992

Streptozocin-doxorubicin, streptozocin-fluorouracil or chlorozotocin in the treatment of advanced islet-cell carcinoma.

BACKGROUND: The combination of streptozocin and fluorouracil has become the standard therapy for advanced islet-cell carcinoma. However, doxorubicin has also been shown to be active against this type of tumor, as has chlorozotocin, a drug that is structurally similar to streptozocin but less frequently causes vomiting. METHODS: In this multicenter trial, we randomly assigned 105 patients with advanced islet-cell carcinoma to receive one of three treatment regimens: streptozocin plus fluorouracil, streptozocin plus doxorubicin, or chlorozotocin alone. The 31 patients in whom the disease did not respond to treatment were crossed over to chlorozotocin alone or to one of the combination regimens. RESULTS: Streptozocin plus doxorubicin was superior to streptozocin plus fluorouracil in terms of the rate of tumor regression, measured objectively (69 percent vs. 45 percent, P = 0.05), and the length of time to tumor progression (median, 20 vs. 6.9 months; P = 0.001). Streptozocin plus doxorubicin also had a significant advantage in terms of survival (median, 2.2 vs. 1.4 years; P = 0.004) that was accentuated when we considered long-term survival (greater than 2 years). Chlorozotocin alone produced a 30 percent regression rate, with the length of time to tumor progression and the survival time equivalent to those observed with streptozocin plus fluorouracil. Crossover therapy after the failure of either chlorozotocin alone or one of the combination regimens produced an overall response rate of only 17 percent, and the responses were transient. Toxic reactions to all regimens included vomiting, which was least severe with chlorozotocin; hematologic depression; and, with long-term therapy, renal insufficiency. CONCLUSIONS: The combination of streptozocin and doxorubicin is superior to the current standard regimen of streptozocin plus fluorouracil in the treatment of advanced islet-cell carcinoma. Chlorozotocin alone is similar in efficacy to streptozocin plus fluorouracil, but it produces fewer gastrointestinal side effects than the regimens containing streptozocin. It therefore merits study as a constituent of combination drug regimens.

Adenoma, Islet Cell↗

PubMed1992

Designs and analysis of two-stage studies.

This paper concerns the design and analysis of two-stage studies, where, at the first stage, the response and the exposure variables are available among a large group of subjects. The other covariables, however, are available in only a subset of the large group, obtained in a second-stage sample. This paper introduces a class of twelve such two-stage designs, including two-stage case-control and case-cohort designs as special cases. In analysing such two-stage data, one objective is to extract information about the relationship between the exposure variable and the response after controlling for other covariables. We discuss three statistical methods to analyse the data and report results of Monte Carlo stimulation to study the efficiency of the three methods.

Case-Control Studies↗

PubMed1992

Physicians' perceptions of the risk of being sued.

We explore the deterrent effect of the tort system by assessing physician perceptions of the risk of being sued and the impact of those perceptions on their own practice. The data are from a mailed survey conducted in 1989 of a random sample of physicians who were practicing in New York State in 1984. The survey results were compared to the actual risk of suit using the between-group (Wald) test and logistic regression methods. We also surveyed physicians about practice changes undertaken in the last ten years, factors influencing practice standards, and the costs of being sued and included these in the analysis. On average, physicians estimate that 19.5 out of one hundred of their colleagues will be sued in a given year, approximately three times the actual rate, with significant differences by specialty, location, and suit history. Perceived risk is associated with self-reported changes in test-ordering frequency and reduction in practice scope. The median number of days lost from practice to defend a malpractice suit was three to five, and 6 percent of the physicians surveyed incurred some out-of-pocket expenses. These findings suggest that physicians respond to the messages sent by litigation in a manner consistent with the deterrent theory of tort litigation.

Age Factors↗

PubMedDate not supplied

Issues in the analysis of repeated categorical outcomes.

This paper discusses statistical methods for the analysis of repeated observations of categorical variables as they might arise in longitudinal studies. Two general types of models are described: marginal models that give representations for the marginal distribution of response at each occasion, and transitional models that give representations for the transition probabilities between outcome states at successive occasions. The conceptual and technical differences are discussed and recent work advancing both approaches is reviewed. The two approaches are illustrated through analysis of repeated observations on interval history of the respiratory symptom 'persistent wheeze' in preadolescent children.

Asthma↗