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Biomedical subjects

W Willett

Publications and source records attributed to W Willett.

At least 73 records · Page 4Linked to original sources
PubMed1986

Total energy intake: implications for epidemiologic analyses.

Associations between intake of specific nutrients and disease cannot be considered primary effects of diet if they are simply the result of differences between cases and noncases in body size, physical activity, and metabolic efficiency. Epidemiologic studies of diet and disease should therefore be directed at the effect of nutrient intakes independent of total caloric intake in most instances. This is not accomplished with nutrient density measures of dietary intake but can be achieved by employing nutrient intakes adjusted for caloric intake by regression analysis. While pitfalls in the manipulation and interpretation of energy intake data in epidemiologic studies have been emphasized, these considerations also highlight the usefulness of obtaining a measurement of total caloric intake. For instance, if a questionnaire obtained information on only cholesterol intake in a study of coronary heart disease, it is possible that no association with disease would be found even if a real positive effect of a high cholesterol diet existed, since the caloric intake of cases is likely to be less than that of noncases. Such a finding could be appropriately interpreted if an estimate of total caloric intake were available. The relationships between dietary factors and disease are complex. Even with carefully collected measures of intake, consideration of the biologic implications of various analytic approaches is needed to avoid misleading conclusions.

Adult↗
PubMed1985

A case-control study of BCG and childhood tuberculosis in Cali, Colombia.

We conducted a case-control study to evaluate the effectiveness of BCG vaccination in preventing childhood tuberculosis (TB) in Cali, Colombia. We ascertained 178 cases aged 0 to 14 years from the respiratory clinics with cough or fever for at least three weeks and a positive chest X-ray for TB, as well as 320 controls who were from the same households but had no symptoms and negative X-rays. Using matched set multiple logistic regression analysis, we found the age- and sex-adjusted relative risk (RR) of TB among vaccinees compared with non-vaccinees to be 0.84 with 95% confidence limits (CL) from 0.43 to 1.62. There was, however, a significantly lowered relative risk of TB with increasing time since vaccination (RR = 0.83 per year since time of vaccination with 95% CL from 0.74 to 0.94.)

Adolescent↗
PubMed1985

Vitamin A and selenium intake in relation to human cancer risk.

The possibility that dietary intake of certain vitamins and minerals may influence the occurrence of human cancer is receiving considerable scientific attention. One prominent hypothesis, that increased dietary intake of vitamin A reduces the occurrence of cancer, has received support from a large number of epidemiologic studies in which an inverse association was observed. The largest body of evidence relates to lung cancer. However, when examined in further detail, this apparent protective effect appears primarily attributable to higher intakes of green and yellow vegetables, which contain the carotenoid precursors of vitamin A. In contrast, there is little evidence to support an association between preformed vitamin A intake and cancer risk. In several studies based on prospectively collected sera, retinol levels were inversely related to subsequent cancer risk. However, these have not been supported by further investigations and appear to be the result of methodologic artifact. Available evidence thus suggests that factors associated with green and yellow vegetables provides modest protection against certain forms of cancer; beta-carotene is a likely candidate and is the focus of considerable research activity. Stimulated by the results of many animal studies and ecologic comparisons, we and other investigators have examined the association of serum selenium levels with subsequent risk of cancer. In the three published prospective studies an inverse association was observed, with a 2-to 5-fold increase in overall cancer risk among those with lowest selenium levels. As would be predicted by animal studies, the combination of low selenium and low vitamin E appears to be particularly deleterious.(ABSTRACT TRUNCATED AT 250 WORDS)

Carotenoids↗
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

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

Dietary animal fat in relation to ovarian cancer risk.

Food and beverage frequency questionnaires were administered to 215 white women with epithelial ovarian cancer and to 215 control women matched by age, race, and residence. Women with ovarian cancer favored foods higher in animal fats and consumed significantly greater amounts of animal fat and significantly less vegetable fat compared with control subjects. Adjusted for potential confounding due to differences between case and control subjects in weight and parity, there was a significant trend for increasing risk for ovarian cancer with increasing animal fat consumption. No major differences were noted between patients and control subjects in coffee, alcohol, and tobacco use. Dietary factors may partially explain variation in the international incidence of this disease and suggest a new pathway for its etiology.

Alcohol Drinking↗
PubMed1983

Effects of cigarette smoking on fasting triglyceride, total cholesterol, and HDL-cholesterol in women.

We examined the relationships of cigarette smoking with fasting triglycerides, total cholesterol, and high-density lipoprotein cholesterol (HDL-C) levels among a group of 191 white women aged 20 to 40 years. The mean triglyceride level among current smokers was 100.0 mg/100 ml and among nonsmokers was 68.4 mg/dl (p less than 0.005). Mean total cholesterol values among current smokers and nonsmokers were, respectively, 197.0 and 189.1 mg/dl (p less than 0.1). Mean HDL-C levels were 45.0 mg/dl among women who were smoking and 52.1 mg/dl among nonsmokers (p less than 0.005). Simultaneous adjustments for the effects of age, weight, height, blood glucose, resting pulse, and oral contraceptive use did not materially alter these relationships. A modest portion of the effect of cigarette smoking on risk of coronary heart disease may be explained by an adverse effect of cigarette smoking on blood lipids.

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↗
PubMed1982

Oral contraceptive use and malignant melanoma.

There was no overall relationship between a prior history of oral contraceptive (OC) use and the development of melanoma among 141 cases of nonfatal malignant melanoma and 2,820 age-matched controls drawn from respondents to a large postal survey of registered U.S. nurses; crude relative risk (RR) was 0.93 and 95% confidence limits (CL) were between 0.64 and 1.36. Adjustment for a number of additional variables did not alter this estimate materially. Duration of OC use and interval since first use were similarly unrelated to the occurrence of melanoma. For women diagnosed before age 40, there was a crude positive association of "ever" use of OC and melanoma (RR = 1.78; 95% CL, 1.11-2.86). However, adjustment for geography and other variables diminished this association and rendered it statistically not significant (RR = 1.43, 95% CL, 0.83-2.46). These data do not support the hypothesis that OC use is an independent risk factor for melanoma.

Adult↗
PubMed1981

Vitamin supplement use among registered nurses.

A dietary questionnaire which included items relating to the use of specific vitamin preparations was sent to a randomly selected group of 2000 female, registered nurses aged 30 to 59 yr residing in 10 states. Among the 1742 women (87%) who returned completed questionnaires, the rates of use were 38% for multiple vitamins, 4% for specific preparations of vitamin A, 23% for vitamin C, and 15% for vitamin E. Women who used specific preparations of vitamins A, C, and E generally consumed them in quantities many times greater than the RDA. Use of specific vitamin preparations was found to increase with age and was highest in California.

Adult↗
PubMed1981

Early age at first birth and decreased risk of breast cancer.

The relationship between age at birth of a first child and breast cancer was evaluated for 1159 affected women and 11,590 women without cancer in data collected in 1976 among married female registered nurses residing in 11 states in the United States. A positive trend of increasing risk of breast cancer with later ages at first birth was found (chi 2(1) for trend in proportions = 30.9, p less than 0.01). Adjustment for potential confounding variables by multiple logistic regression did not affect this trend. The presence of this relationship using non-hospitalized controls of similar social status to cases supports the reality of this association, which has recently been challenged as an artifact due to inappropriate choice of hospitalized controls.

Adult↗
PubMed1981

Use of postmenopausal hormones and risk of myocardial infarction.

Information was collected by mail survey about myocardial infarction (MI), use of female hormones after menopause, and coronary risk factors 121,964 registered nurses ages 30-55 years. One hundred twenty-three women with a known type of prior menopause reported hospitalization for MI. Overall, use of female hormones by these women was very similar to that of control women matched for age and type of menopause. Compared with nonusers, the relative risk (RR) for women who had ever taken female hormones was 0.9 (95% confidence limits 0.6-1.2), and for current users the RR was 0.7 (0.5-1.1). For women with bilateral oophorectomy, the RR for current users was 0.4 (0.2-0.8). These data imply that, at present, a decision to prescribe postmenopausal hormones should be based primarily on weighing possible benefits from the relief of menopausal symptoms against unknown or suspected risks of other diseases, particularly uterine cancer in women with an intact uterus.

Adult↗
PubMed1979

Effects of beer, wine, and liquor in coronary deaths.

For a series of 568 married men who died of coronary heart disease and an equal number of matched control subjects, information was collected on a large number of variables, including daily alcohol consumption classified by type of beverage, namely, beer, wine, or liquor. Daily consumption of small to moderate amounts of alcohol (2 oz [59.2mL] or less daily) was inversely related to coronary death. This inverse relation was present in both crude and adjusted matched-pair analyses and was similar for each type of alcohol, as indicated by adjusted relative risks of 0.3 for beer, 0.3 for wine, and 0.2 for liquor. In contrast, for heavy drinking, there was no association with coronary death in either crude or adjusted analyses.

Adult↗