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Biomedical subjects

M J Stampfer

Publications and source records attributed to M J Stampfer.

At least 487 records · Page 27Linked to original sources
PubMed1985

Reproducibility and validity of a semiquantitative food frequency questionnaire.

The aim of this study was to evaluate the reproducibility and validity of a 61-item semiquantitative food frequency questionnaire used in a large prospective study among women. This form was administered twice to 173 participants at an interval of approximately one year (1980-1981), and four one-week diet records for each subject were collected during that period. Intraclass correlation coefficients for nutrient intakes estimated by the one-week diet records (range = 0.41 for total vitamin A without supplements to 0.79 for vitamin B6 with supplements) were similar to those computed from the questionnaire (range = 0.49 for total vitamin A without supplements to 0.71 for sucrose), indicating that these methods were generally comparable with respect to reproducibility. With the exception of sucrose and total carbohydrate, nutrient intakes from the diet records tended to correlate more strongly with those computed from the questionnaire after adjustment for total caloric intake. Correlation coefficients between the mean calorie-adjusted intakes from the four one-week diet records and those from the questionnaire completed after the diet records ranged from 0.36 for vitamin A without supplements to 0.75 for vitamin C with supplements. Overall, 48% of subjects in the lowest quintile of calorie-adjusted intake computed from the diet records were also in the lowest questionnaire quintile, and 74% were in the lowest one of two questionnaire quintiles. Similarly, 49% of those in the highest diet record quintile were also in the highest questionnaire quintile, and 77% were in the highest one or two questionnaire quintiles. These data indicate that a simple self-administered dietary questionnaire can provide useful information about individual nutrient intakes over a one-year period.

Adult↗
PubMed1985

Relative weight and risk of breast cancer among premenopausal women.

Although higher relative weight is generally considered to increase the risk of breast cancer, several case-control studies have suggested that the reverse may be true among premenopausal women. The association between Quetelet's index (a measure of relative weight calculated as weight/height) and the subsequent incidence of breast cancer was therefore examined during four years of follow-up among a cohort of 121,964 US women who were 30-55 years of age in 1976. In contrast to women who had experienced natural menopause or bilateral oophorectomy, the incidence of breast cancer among premenopausal women decreased with higher levels of relative weight. Age-adjusted relative risks for increasing quintiles of Quetelet's index were 1.00, 0.90, 0.90, 0.73, and 0.66 (Mantel extension test for trend = -2.82, p = 0.005). This inverse association was not explained by known risk factors for breast cancer and was somewhat stronger when Quetelet's index was computed using reported weight at age 18 years. The excess incidence of breast cancer among lean premenopausal women, however, was limited to tumors that were less than 2.0 cm in diameter, were not associated with metastases to lymph nodes, and were well-differentiated. These findings suggest that the apparent excess risk of breast cancer among lean premenopausal women may result at least in part from easier, and thus earlier, diagnosis of less aggressive tumors.

Adult↗
PubMed1985

Intravenous and intracoronary fibrinolytic therapy in acute myocardial infarction: overview of results on mortality, reinfarction and side-effects from 33 randomized controlled trials.

During the past 25 years, 24 randomized trials of intravenous (IV) fibrinolytic treatment have been reported, involving a total of some 6000 patients in the acute phase of myocardial infarction. Most tested IV streptokinase (SK), but a few tested IV urokinase (UK). In the past 2 or 3 years numerous small randomized trials of intracoronary (IC) SK have been started, 9 of which, involving a total of about 1000 such patients, have been reported. Because all of these IV and IC trials were small (the largest including only 747 patients), their separate results appear contradictory and unreliable. But, an overview of the data from these trials indicates that IV treatment produces a highly significant (22% +/- 5%, P less than 0.001) reduction in the odds of death, an even larger reduction in the odds of reinfarction, and an absolute frequency of serious adverse effects to set against this that is much smaller than the absolute mortality reduction. The apparent size of the mortality reduction in the IV trials was similar whether anticoagulants were compulsory or optional, whether treatment was in a coronary care unit or an ordinary ward and, surprisingly, whether treatment began early (less than 6 h from onset of symptoms) or late (generally 12-24 h). In addition, there was no evidence that UK was more effective than the less expensive SK, or that, despite their technical complexity, the new IC regimes were more effective than the old IV regimes. Even the IV schedules that have been studied in randomized trials were, however, quite complex, and the IC schedules were far more so. Perhaps partly because of this, none of them is widely used. If so, then some much simpler, and hence more widely practicable, IV SK regimes should be developed and tested. For example, a simple one hour high-dose IV SK infusion, without anticoagulation, will successfully convert virtually all of the available plasminogen into plasmin. But, it may be several years before the net effects on mortality of any more widely practicable IV SK regimes can be agreed unless many of the hospitals that do not wish routinely to use IC regimes or the complex previous IV regimes will collaborate in multicentre randomized trials that can, if necessary, continue rapid intake until some tens of thousands of patients have been randomized, and some thousands of deaths have been observed among the control and treated patients. The same, of course, may be true for any other fibrinolytic regimes (e.g. infusion of tissue plasminogen activator) if their net effects on mortality are comparable to those of IV SK.

Anticoagulants↗
PubMed1985

Cumulative antiplatelet effect of low-dose enteric coated aspirin.

Enteric coated aspirin (ECA) at doses of 325-1300 mg is an effective alternative to regular aspirin for inhibition of platelet activity while avoiding gastric irritation. The objectives of this study were to determine: (1) the lowest chronic dose of ECA providing effective inhibition of platelet activities, (2) the time course of the inhibition, and (3) the reappearance of platelet cyclo-oxygenase activity. Seven subjects were studied before and after seven daily doses of 40-325 mg ECA. Serum thromboxane (TX) B2 levels indicated that the lowest dose of ECA resulting in greater than 90% inhibition of platelet cyclo-oxygenase was 80 mg/d. Platelet aggregation and ATP release in response to collagen (1 microgram/ml) and arachidonic acid (1 mM) were abolished and bleeding times were prolonged from 6.1 +/- 1.5 min to 9.7 +/- 2.8 min (mean +/- SD, P less than 0.01). Examination of platelet cyclo-oxygenase activity on a daily basis revealed that 24 h after the first 80 mg dose serum TXB2 had decreased by approximately 60% and was suppressed by more than 90% after four doses. Recovery of platelet cyclo-oxygenase activity after a single 80 mg dose of ECA was delayed for 48-72 h indicating that aspirin reached the systemic circulation. We conclude that chronic inhibition of platelet activity may be achieved in a cumulative manner with 80 mg ECA/d.

Adenosine Triphosphate↗
PubMed1984

Relation of serum vitamins A and E and carotenoids to the risk of cancer.

Epidemiologic studies suggest that low carotene intake and low levels of serum retinol may be associated with an increased risk of cancer. Likewise, in some animal studies vitamin E has been associated with a reduced rate of induced cancers. Therefore, we measured retinol, retinol-binding protein, vitamin E (alpha-tocopherol), and total carotenoids in serum collected in 1973 from 111 participants in the Hypertension Detection and Follow-up Program who were free of cancer at the time but were diagnosed as having cancer during the subsequent five years. These measurements were compared with those in 210 controls who were matched for age, sex, race, and time of blood collection, and who remained free of cancer. Mean values for retinol were similar for cases and controls (67.3 and 68.7 micrograms per deciliter, respectively [95 per cent confidence limits for case-control difference, -6.7 to 3.5]). Values were also similar for retinol-binding protein (6.01 and 5.94 mg per deciliter [-0.42 to 0.56]), and carotenoids (114.5 and 111.6 micrograms per deciliter [-9.1 to 15.9]). The mean base-line retinol level in the 18 subjects with subsequent lung cancer was higher than that in their matched controls (79.0 vs. 71.4 micrograms per deciliter, -4.9 to 19.7). Serum vitamin E levels were somewhat lower in subjects who later had cancer than in controls (1.16 and 1.26 mg per deciliter, -0.22 to 0.02), in part because of the confounding effect of serum cholesterol levels (when adjusted for lipid levels, the case-control difference was -0.05 mg per deciliter; -0.17 to 0.07). These data do not support hypotheses relating intake or serum levels of antioxidant vitamins to a reduced cancer risk.

Adult↗
PubMed1984

A case-control study of risk indicators among women with premenopausal and early postmenopausal breast cancer.

Among 714 premenopausal and 130 postmenopausal breast cancer cases matched with 8440 controls for age in years and menopausal status, risk indicators for breast cancer were similar, although most associations were stronger in the premenopausal women. Compared with nulliparous women, the relative risk (RR) for those with first birth before age 25 years was 0.7 (95% confidence limits [CL] from 0.5 to 0.9) among premenopausal women, and 0.7 (0.4-1.4) for postmenopausal women. In the premenopausal cases, a history of breast cancer in a sister gave a RR of 3.0 (2.1-4.1) and in a mother 1.9 (1.4-2.5), whereas for the postmenopausal women the RRs were 1.4 (0.6-3.1) and 1.3 (0.6-2.6), respectively. Fibrocystic breast disease was also a significant predictor of subsequent breast cancer in the premenopausal and postmenopausal women. In relation to women having a single birth, premenopausal women with six or more births had a risk of breast cancer of 0.6 (0.4-1.0), which was present even after adjustment for age at first birth.

Age Factors↗
PubMed1984

The prognostic significance of proteinuria: the Framingham study.

Despite considerable clinical experience with proteinuria, its prognostic meaning in the ambulatory general population is poorly documented. From a 16-year study of 5209 men and women in the Framingham cohort it is evident that proteinuria, even in casual urine specimens, carries substantial risk with the mortality rate increased threefold. Proteinuria was three times as common in hypertensive persons and also occurred to excess in diabetic patients and in persons with cardiac enlargement. In the absence of these factors, proteinuria was so uncommon that its risk could not be accurately assessed. Among persons with these associated risk factors, those with proteinuria have higher death rates than those without proteinuria. In men, overall mortality and cardiovascular mortality rates remained significantly increased even when other contributors to risk were taken into account. Proteinuria in the ambulatory general population is not a benign condition and carries a serious prognosis. It appears to reflect widespread vascular damage.

Adult↗
PubMed1984

A case-control study of oral contraceptive use and breast cancer.

Among 989 cases of breast cancer and 9,890 controls selected from a cohort of married, female registered nurses aged 30-55 years, the relative risk (RR) of breast cancer for women who had ever used oral contraceptives (OC) compared with those who had never used them was 1.0, with 95% confidence limits 0.9-1.2. Among OC users, there was no consistent pattern of excess risk with increasing duration; in fact, the few women who had used OC longest (greater than 10 yr) had a slightly lower risk than never-users. Moreover, there was no association between OC use and breast cancer among women with a positive history of breast cancer in the mother or sister or with OC use before their first pregnancy. The only subgroup of women among whom any adverse effect was apparent was current OC users aged 50-55 years (two onsets expected vs. seven observed). This finding is consistent with earlier reports of an increased risk of breast cancer among older OC users; however, it is also likely to reflect, at least to some extent, the play of chance, since at ages 45-49 and in each younger age group fewer cases than expected were observed among current OC users.

Adult↗
PubMed1984

Micronutrients and cancer chemoprevention.

Accumulating evidence suggests that a number of micronutrients may decrease the incidence of cancer of epithelial cell origin. These include vitamins A, C and E, beta-carotene and selenium. Few lines of research, apart from means to reduce cigarette smoking or heavy alcohol consumption, are as promising in terms of substantially decreasing human cancer incidence as studies of such micronutrients as dietary inhibitors of cancer. In this paper, we review the mechanisms by which these micronutrients may act to inhibit carcinogenesis, as well as the current animal and epidemiologic evidence supporting their role as chemopreventive agents. With respect to areas of future study, valuable information can be obtained from basic research as well as observational analytic epidemiologic studies utilizing dietary questionnaires which are more specifically focused and have been more rigorously evaluated than those previously employed. Another promising avenue of epidemiologic research is prospective studies of cancer incidence in relation to biochemical parameters in stored blood samples collected at baseline. The most reliable way to test directly whether a micronutrient prevents the development of human cancer is a large, randomized placebo-controlled trial among individuals with no previous history of the disease. The timely conduct of such trials is particularly important, since regular intake of nutritional supplements is already widespread in the United States, despite the lack of reliable evidence as to their benefits.

Ascorbic Acid↗
PubMed1984

Vitamin A supplementation and plasma retinol levels: a randomized trial among women.

Although dietary intake of vitamin A has little, if any, overall effect on blood retinol in generally well-nourished populations, subgroups may exist that would be responsive to supplementation. The hypothesis that vitamin A supplementation increases blood retinol in apparently well-fed individuals with lower than usual blood levels was tested in female health workers, with relatively low blood retinol values, who were randomly assigned to receive vitamin A (10,000 IU daily) or placebo. After 4 weeks the mean change in plasma retinol was -0.4 micrograms/dl for the group receiving placebo and +4.1 micrograms/dl (an increase of 9% over base-line values) for the group receiving vitamin A (P = .02). The results were similar when the base-line retinol level and several other covariates were considered. Thirteen women who had initially received placebo were then switched to vitamin A for 4 weeks. These women experienced a mean increase of 5.3 micrograms/dl in plasma retinol (P = .04). Responses to vitamin A supplementation tend to be greater among women with lower previous total vitamin A intake, as assessed by questionnaire [Spearman rank correlation coefficient (r) = 0.50; P = .01].

Breast Neoplasms↗
PubMed1984

Some factors affecting determination of carotenoids in serum.

Because of increasing interest in carotenoid pigments, we conducted a study of the methods of determining carotenoids in serum. We found 1 mol of KOH per liter of absolute methanol to be the most effective saponifying solution. The absorbance of beta-carotene in petroleum ether, the extraction solvent, is proportional to dilution up to an absorbance of 0.85 at 450 nm. Beta-carotene in petroleum ether solution is not impracticably sensitive to ambient light at room temperature. However, if vitamin A is also to be measured in these serum specimens or petroleum ether extracts, exposure to light should be minimized. We found that serum may be shipped either in cold packs or at ambient temperature (tested up to five days) without significant change in carotenoid concentration. Serum samples for carotenoid determination are best stored at -70 degrees C: samples stored at -20 degrees C deteriorate substantially over several months.

Carotenoids↗
PubMed1983

Prediagnostic serum selenium and risk of cancer.

Selenium levels in serum samples collected in 1973 from 111 subjects in whom cancer developed during the subsequent 5 years were compared with those in serum samples from 210 cancer-free subjects matched for age, race, sex, and smoking history. The mean selenium level of cases (0.129 +/- SEM 0.002 micrograms/ml) was significantly lower than that of controls (0.136 +/- 0.002 micrograms/ml). The risk of cancer for subjects in the lowest quintile of serum selenium was twice that of subjects in the highest. Multivariate adjustment for geographical area and serum levels of lipids, vitamins A and E, and carotene, did not alter this relation. The association between low selenium level and cancer was strongest for gastrointestinal and prostatic cancers. Serum levels of vitamins A and E compounded the effect of low selenium; relative risks for the lowest tertile of selenium were 2.4 and 3.9 in the lowest tertiles of vitamins E and A, respectively.

Adult↗
PubMed1983

Vitamins A, E, and carotene: effects of supplementation on their plasma levels.

We conducted a randomized, double-blind trial among 59 generally well-nourished adults to determine the effects of vitamin A, vitamin E, and beta-carotene supplements on plasma retinol, alpha-tocopherol, and carotenoid levels. Over a period of 16 wk a daily alpha-tocopherol supplement of 800 IU approximately doubled plasma alpha-tocopherol levels (p less than 0.001), caused a small decrease in plasma carotenoids (p = 0.02), and produced a slight and statistically insignificant reduction in plasma retinol. A daily beta-carotene supplement of 30 mg (5000 retinol equivalents) approximately tripled plasma carotenoid levels (p less than 0.001) but did not affect plasma retinol or alpha-tocopherol. A daily retinyl palmitate supplement of 25,000 IU (13,750 retinol equivalents) did not appreciably affect plasma retinol, alpha-tocopherol, or carotenoid.

Adult↗
PubMed1983

Validation of a dietary questionnaire with plasma carotenoid and alpha-tocopherol levels.

We assessed the validity of a self-administered semiquantitative food frequency questionnaire by comparing carotene and vitamin E intake scores derived from form with plasma carotenoid and alpha-tocopherol levels among a group of 59 men and women. The simple correlation between carotene intake and plasma carotenoid was 0.29 (p = 0.02) and the partial correlation was 0.35 (p = 0.005) after adjustment for age, sex, total caloric intake, and plasma cholesterol and triglycerides. The simple correlation between vitamin E intake and plasma alpha-tocopherol was 0.12 (p = 0.19). However, adjustment for total caloric intake and plasma lipids each substantially increased this association so that the partial correlation adjusting simultaneously for caloric intake, plasma lipids, age, and sex was 0.34 (p = 0.006). As expected on the basis of previous randomized trials, the correlation between preformed vitamin A intake and plasma retinol was weak and not statistically significant. These data support the utility of self-administered food frequency questionnaires for use in epidemiological studies. In addition, they illustrate the importance of adjusting blood alpha-tocopherol levels for lipid concentrations when the former are used as surrogates for vitamin E intake.

Adult↗
PubMed1983

Effect of vitamin E on lipids.

A recent clinical report noted that vitamin E administration was followed by a dramatic elevation of high-density lipoprotein cholesterol (HDL-C). Since HDL-C is inversely associated with coronary heart disease, we conducted a randomized, double-blind, placebo-controlled clinical trial of vitamin E administration (800 IU/day) for 16 weeks. The subjects were 30 adults aged 30-60 years, with 15 participants in each group. We measured fasting HDL-C, total cholesterol, and triglycerides at baseline and at 8 and 16 weeks. Vitamin E had no effect on HDL-C; the mean changes at 8 and 16 weeks in the placebo group were -0.3 mg/dL and -2.6 mg/dL, and in the vitamin E group -0.4 and -0.9 mg/dL. Aside from a marginal decrease in calculated low-density lipoprotein cholesterol, at 16 weeks there were no significant differences for any of the lipids. These data, in conjunction with other information in the literature, indicate that vitamin E does not alter plasma lipids in normal adults.

Adult↗
PubMed1983

Cigarette smoking, relative weight, and menopause.

To examine the interrelationships of cigarette smoking, relative weight, and the occurrence of natural menopause, the authors prospectively evaluated the experience of 66,663 female US registered nurses who were premenopausal in 1976. Over a two-year period, 5004 women became post-menopausal. Current smokers were more likely than past or never smokers to develop menopause, although the effects of smoking diminished with age. The rate ratios of menopause for current smokers vs. never smokers (with 95% confidence limits) for women aged 30-39, 40-44, 45-49, and 50-55 years were 1.90 (1.10-3.28), 2.16 (1.73-2.69), 1.53 (1.41-1.67), and 1.20 (1.12-1.28). These rate ratios were not appreciably affected by adjustment for relative weight. Median ages at menopause were 52.4 for never smokers and 51.9, 51.0, 50.7, and 50.4 years for women who currently smoked 1-14, 15-24, 25-34, and 35 or more cigarettes per day. A crude linear relationship between relative weight and occurrence of menopause was observed. Comparing the leanest and heaviest quintiles, rate ratios for menopause among women aged 30-39, 40-44, 45-49, and 50-55 years were 1.42 (0.74-2.75), 1.26 (0.95-1.69), 1.25 (1.13-1.41) and 1.08 (0.99-1.19). The effect of relative weight was in part explained by the tendency of current smokers to weigh less than nonsmokers. After adjustment for current cigarette consumption a weak linear relationship between relative weight and menopause remained among women who smoked, although no such association was seen among nonsmokers.

Adult↗