Biomedical subjects

G E Fraser

Publications and source records attributed to G E Fraser.

At least 19 recordsLinked to original sources

PubMed2005

A comparison of first event coronary heart disease rates in two contrasting California populations.

OBJECTIVES: To directly evaluate whether a population, many of whom are vegetarian or near vegetarian, does experience less coronary heart disease (CHD). METHODS: Two concurrent California observational studies,one with unusual dietary habits, are compared. Similar diagnostic criteria were used in both the Adventist Health Study and the Stanford Five-City Project. RESULTS: Age-standardized rate ratios (Adventist/Stanford study) for first event fatal CHD were 0.59 (95% confidence interval,0.43-0.80) in men and 0.49(0.32-0.76) in women. Similar ratios for first event myocardial infarction were 0.60(0.47-0.78) and 0.46 (0.33-0.65). Ratios are usually much lower at younger ages or when comparisons include only vegetarian Adventists. CONCLUSION: Lifestyle factors can markedly change the first-event CHD experience of whole populations, and appear to especially protect against premature events.

Age Factors↗

PubMed2001

Regression calibration in studies with correlated variables measured with error.

Regression calibration is a technique that corrects biases in regression results in situations where exposure variables are measured with error. The existence of a calibration substudy, where accurate and crude measurement methods are related by a second regression analysis, is assumed. The cost of measurement error in multivariate analyses is loss of statistical power. In this paper, calibration data from California Seventh-day Adventists are used to simulate study populations and new calibration studies. Applying regression calibration logistic analyses, the authors estimate power for pairs of nutritional variables. The results demonstrate substantial loss of power if variables measured with error are strongly correlated. Biases in estimated effects in cases where regression calibration is not performed can be large and are corrected by regression calibration. When the true coefficient has zero value, the corresponding coefficient in a crude analysis will usually have a nonzero expected value. Then type I error probabilities are not nominal, and the erroneous appearance of statistical significance can readily occur, particularly in large studies. Major determinants of power with use of regression calibration are collinearity between the variables measured with error and the size of correlations between crude and corresponding true variables. Where there is important collinearity, useful gains in power accrue with calibration study size up to 1,000 subjects.

Bias↗

PubMed2001

Ten years of life: Is it a matter of choice?

BACKGROUND: Relative risk estimates suggest that effective implementation of behaviors commonly advocated in preventive medicine should increase life expectancy, although there is little direct evidence. OBJECTIVE: To test the hypothesis that choices regarding diet, exercise, and smoking influence life expectancy. METHODS: A total of 34 192 California Seventh-Day Adventists (75% of those eligible) were enrolled in a cohort and followed up from 1976 to 1988. A mailed questionnaire provided dietary and other exposure information at study baseline. Mortality for all subjects was ascertained by matching to state death tapes and the National Death Index. RESULTS: California Adventists have higher life expectancies at the age of 30 years than other white Californians by 7.28 years (95% confidence interval, 6.59-7.97 years) in men and by 4.42 years (95% confidence interval, 3.96-4.88 years) in women, giving them perhaps the highest life expectancy of any formally described population. Commonly observed combinations of diet, exercise, body mass index, past smoking habits, and hormone replacement therapy (in women) can account for differences of up to 10 years of life expectancy among Adventists. A comparison of life expectancy when these factors take high-risk compared with low-risk values shows independent effects that vary between 1.06 and 2.74 years for different variables. The effect of each variable is assessed with all others at either medium- or high-risk levels. CONCLUSIONS: Choices regarding diet, exercise, cigarette smoking, body weight, and hormone replacement therapy, in combination, appear to change life expectancy by many years. The longevity experience of Adventists probably demonstrates the beneficial effects of more optimal behaviors.

Adult↗

PubMed2001

Types of dietary fat and breast cancer: a pooled analysis of cohort studies.

Recently, there has been interest in whether intakes of specific types of fat are associated with breast cancer risk independently of other types of fat, but results have been inconsistent. We identified 8 prospective studies that met predefined criteria and analyzed their primary data using a standardized approach. Holding total energy intake constant, we calculated relative risks for increments of 5% of energy for each type of fat compared with an equivalent amount of energy from carbohydrates or from other types of fat. We combined study-specific relative risks using a random effects model. In the pooled database, 7,329 incident invasive breast cancer cases occurred among 351,821 women. The pooled relative risks (95% confidence intervals [CI]) for an increment of 5% of energy were 1.09 (1.00-1.19) for saturated, 0.93 (0.84-1.03) for monounsaturated and 1.05 (0.96-1.16) for polyunsaturated fat compared with equivalent energy intake from carbohydrates. For a 5% of energy increment, the relative risks were 1.18 (95% CI 0.99-1.42) for substituting saturated for monounsaturated fat, 0.98 (95% CI 0.85-1.12) for substituting saturated for polyunsaturated fat and 0.87 (95% CI 0.73-1.02) for substituting monounsaturated for polyunsaturated fat. No associations were observed for animal or vegetable fat intakes. These associations were not modified by menopausal status. These data are suggestive of only a weak positive association with substitution of saturated fat for carbohydrate consumption; none of the other types of fat examined was significantly associated with breast cancer risk relative to an equivalent reduction in carbohydrate consumption.

Breast Neoplasms↗

PubMed2001

Intake of fruits and vegetables and risk of breast cancer: a pooled analysis of cohort studies.

CONTEXT: Some epidemiologic studies suggest that elevated fruit and vegetable consumption is associated with a reduced risk of breast cancer. However, most have been case-control studies in which recall and selection bias may influence the results. Additionally, publication bias may have influenced the literature on associations for specific fruit and vegetable subgroups. OBJECTIVE: To examine the association between breast cancer and total and specific fruit and vegetable group intakes using standardized exposure definitions. DATA SOURCES/STUDY SELECTION: Eight prospective studies that had at least 200 incident breast cancer cases, assessed usual dietary intake, and completed a validation study of the diet assessment method or a closely related instrument were included in these analyses. DATA EXTRACTION: Using the primary data from each of the studies, we calculated study-specific relative risks (RRs) that were combined using a random-effects model. DATA SYNTHESIS: The studies included 7377 incident invasive breast cancer cases occurring among 351 825 women whose diet was analyzed at baseline. For comparisons of the highest vs lowest quartiles of intake, weak, nonsignificant associations were observed for total fruits (pooled multivariate RR, 0.93; 95% confidence interval [CI], 0.86-1.00; P for trend =.08), total vegetables (RR, 0.96; 95% CI, 0.89-1.04; P for trend =.54), and total fruits and vegetables (RR, 0.93; 95% CI, 0.86-1.00; P for trend =.12). No additional benefit was apparent in comparisons of the highest and lowest deciles of intake. No associations were observed for green leafy vegetables, 8 botanical groups, and 17 specific fruits and vegetables. CONCLUSION: These results suggest that fruit and vegetable consumption during adulthood is not significantly associated with reduced breast cancer risk.

Adult↗

PubMed2001

Comparing biological measurements of vitamin C, folate, alpha-tocopherol and carotene with 24-hour dietary recall information in nonhispanic blacks and whites.

PURPOSE: To assess intake of several vitamins in preparation for a large cohort study investigating the effect of diet on risk of colon and prostate cancer. METHODS: The dietary intake of several vitamins were assessed using eight different 24-hour recalls and a 200-item food frequency questionnaire (FFQ) from each subject. Participants also attended a clinic where blood was drawn and body composition, weight, height, and blood pressure were measured. A total of 97 black and 96 nonhispanic white subjects participated. The levels of alpha-tocopherol, carotene, folate, and vitamin C in the blood were correlated with the dietary intakes as measured by both 24-hour recalls and FFQ. RESULTS: Correlations between blood levels and energy-adjusted dietary intake assessed by 24-hour recalls (with supplements) were as follows: carotene (adjusted for serum cholesterol): 0.47 and 0.55 in black and white subjects, respectively; alpha-tocopherol (adjusted for serum cholesterol): 0.61 (blacks) and 0.50 (whites); vitamin C: 0.22 (blacks) and 0.17 (whites); folate: 0.54 (blacks) and 0.55 (whites). Correlations between blood levels and FFQ indices were smaller in magnitude: 0.34 and 0.28 for carotene in black and white subjects, respectively, 0.37 and 0.56 for alpha-tocopherol (adjusted for serum cholesterol), 0.20 and 0.03 for vitamin C and 0.24 and 0.32 for folate. CONCLUSIONS: The correlations observed were generally of modest to moderate size and were similar to or larger than those reported by others. This is despite variations in absorption, metabolism, and excretion of the vitamins and suggests that both the 24-hour recalls and the FFQ contain valid information.

Black or African American↗

PubMed2001

Validity of a physical activity questionnaire among African-American Seventh-day Adventists.

INTRODUCTION: Physical activity has been identified as an important predictor of chronic disease risk in numerous studies in which activity levels were measured by questionnaire. Although the validity of physical activity questionnaires has been documented in a number of studies of U.S. adults, few have included a validation analysis among blacks. We have examined the validity and reliability of a physical activity questionnaire that was administered to 165 black Seventh-day Adventists from Southern California. METHODS: Subjects completed a self-administered physical activity questionnaire and then "reference" measures of activity (7-d activity recalls, pedometer readings) and fitness (treadmill test) were completed in subsets of this population. RESULTS: The authors found that 7-d recall activity levels correlated well with the corresponding questionnaire indices among women (total activity, r = 0.65; vigorous, r = 0.85; moderate, r = 0.44; inactivity, r = 0.59; sleep duration, r = 0.52) and men (total activity, r = 0.51; vigorous, r = 0.65; moderate, r = 0.53; inactivity, r = 0.69; sleep duration, r = 0.39). Vigorous activity from 7-d recalls was best measured by gender-specific indices that included only recreational activities among men and emphasized nonrecreational activities among women. Correlations between questionnaire data and the other "reference" measures were lower. Test-retest correlations of questionnaire items over a 6-wk interval were high (r = 0.4-0.9). CONCLUSION: Simple questions can measure activities of different intensity with good validity and reliability among black Adventist men and women.

Adult↗

PubMed2000

Urinary 1-methylhistidine is a marker of meat consumption in Black and in White California Seventh-day Adventists.

Meat consumption predicts risk of several chronic diseases. The authors validate the accuracy of meat consumption reported by food frequency questionnaires and the mean of eight 24-hour recalls, using urinary methylhistidine excretion, in 55 Black and 71 White Adventist subjects in Los Angeles and San Diego, California, in 1994-1997. 1-Methylhistidine excretion predicts vegetarian status in Black (p = 0.02) and in White (p = 0.005) subjects. Spearman's correlation coefficients between 1-methylhistidine and estimated meat consumption were usually between 0.4 and 0.6 for both food frequency questionnaires and 24-hour recall data. This is despite the chance collection of dietary recalls and urines from omnivores on meatless days.

Black or African American↗

PubMed2000

The effect of age, sex, and education on food consumption of a middle-aged English cohort-EPIC in East Anglia.

BACKGROUND: Different dietary patterns are associated with differing risks of chronic disease. Yet independent relationships between diet and demographic variables, such as age, sex, and education, are poorly described. METHODS: The first 1968 subjects enrolled to the European Prospective Investigation of Cancer (EPIC) cohort from general practices in East Anglia, UK, provided food frequency and demographic data. RESULTS: Men ate meat, eggs, milk, and sugary foods more frequently, but fruit and vegetables less frequently than women. Older subjects ate red meats and saturated bread spreads more frequently but consumed less poultry and drank less coffee than younger subjects. Better educated subjects ate less meat, more salads, and fewer cakes and sweet foods than those less educated. Five clusters representing different dietary patterns were readily identified. These were (a) younger well-educated, probably containing many vegetarians; (b) "low calorie," two-thirds female; (c) high alcohol, nuts, meat, largely male; (d) preferring fruits, vegetables, unsaturated fats, poultry, and fish, 71% female; (e) preferring meat, potatoes, sweet foods, saturated fats, less well-educated older men. CONCLUSIONS: The reported consumption of many foods varies by age, gender, and education. A pattern of eating that is generally considered less healthful was particularly seen in older men, placing them at increased risk of chronic disease.

Age Factors↗

PubMed1999

Body weight and mortality among adults who never smoked.

In a 12-year prospective study, the authors examined the relation between body mass index (BMI) and mortality among the 20,346 middle-aged (25-54 years) and older (55-84 years) non-Hispanic white cohort members of the Adventist Health Study (California, 1976-1988) who had never smoked cigarettes and had no history of coronary heart disease, cancer, or stroke. In analyses that accounted for putative indicators (weight change relative to 17 years before baseline, death during early follow-up) of pre-existing illness, the authors found a direct positive relation between BMI and all-cause mortality among middle-aged men (minimum risk at BMI (kg/m2) 15-22.3, older men (minimum risk at BMI 13.5-22.3), middle-aged women (minimum risk at BMI 13.9-20.6), and older women who had undergone postmenopausal hormone replacement (minimum risk at BMI 13.4-20.6). Among older women who had not undergone postmenopausal hormone replacement, the authors found a J-shaped relation (minimum risk at BMI 20.7-27.4) in which BMI <20.7 was associated with a twofold increase in mortality risk (hazard ratio (HR) = 2.2, 95% confidence interval (CI) 1.3, 3.5) that was primarily due to cardiovascular and respiratory disease. These findings not only identify adiposity as a risk factor among adults, but also raise the possibility that very lean older women can experience an increased mortality risk that may be due to their lower levels of adipose tissue-derived estrogen.

Adult↗

PubMed1999

The estimation of lifetime risk and average age at onset of a disease using a multivariate exponential hazard rate model.

Readily grasped concepts such as lifetime risk of, and expected age at onset of, a disease, cannot be easily estimated by the relative risk methods commonly used in epidemiology. Here we develop a method for estimating these quantities with confidence intervals, where the likelihood is a multivariate function of exposure variables. The model is basically non-parametric, except for a proportional hazards assumption on exposures, and except for the youngest data-poor ages, where an exponential model in age is assumed. Tests of goodness-of-fit of the model are described, these allowing for product terms between exposures and age. Application of the method is made to the Adventist Health Study cohort, where the independent effects of several exposures on these outcomes are demonstrated.

Adult↗

PubMed1999

Nut consumption, lipids, and risk of a coronary event.

In the past, many have avoided nuts because of their high fat content. The Dietary Approaches to Stop Hypertension (DASH) diet, however, recommends regular consumption of this food along with seeds and dried beans (4-5 servings per week) as part of a diet to control hypertension. Nuts are nutrient-dense and most of their fat is unsaturated. They are also perhaps the best natural source of vitamin E and are relatively concentrated repositories of dietary fiber, magnesium, potassium, and arginine, the dietary precursor of nitric oxide. Human feeding studies have demonstrated reductions of 8-12% in low-density lipoprotein (LDL) cholesterol when almonds and walnuts are substituted for more traditional fats. Other studies show that macadamias and hazelnuts appear at least as beneficial as fats in commonly recommended diets. Whether consuming modest quantities of nuts daily may promote weight gain is not known with certainty, but preliminary data suggest that this is unlikely. Four of the best and largest cohort studies in nutritional epidemiology have now reported that eating nuts frequently is associated with a decreased risk of coronary heart disease of the order of 30-50%. The findings are very consistent in subgroup analyses and unlikely to be due to confounding. Possible mechanisms include reduction in LDL cholesterol, the antioxidant actions of vitamin E, and the effects on the endothelium and platelet function of higher levels of nitric oxide. Although nuts may account for a relatively small percentage of dietary calories, the potential interacting effects of these factors on disease risk may be considerable.

Cholesterol, LDL↗

PubMed1999

Diet as primordial prevention in Seventh-Day Adventists.

Epidemiologic studies of Seventh-Day Adventists have clearly shown that dietary habits are associated with risk of coronary heart disease (CHD) and other chronic diseases. However, a few surprising results emerge. Meat consumption is clearly hazardous for Adventist men by raising CHD mortality. However, no such effect was seen in women. Possible reasons are discussed. Our data, and that of others, strongly support the role of a fatty food, specifically nuts, as protective for CHD. The possible implications of this result for fat intake as a risk factor for CHD are discussed. In particular, it may be that consumption of modest quantities of certain fats is beneficial, rather than hazardous. The lower risk of CHD in Adventists probably has a complicated explanation and certainly cannot be entirely explained by their nonsmoking status or a superior serum lipid profile. Adventists are unique in that the majority of this group have adopted a dietary habit that is either vegetarian or tending in this direction. The power of incorporating health into a system of religious belief is discussed. Possibly others can also implement such a model to their advantage.

California↗

PubMed1999

Age at natural menopause and total mortality and mortality from ischemic heart disease: the Adventist Health Study.

We studied the relationship between age at natural menopause and total mortality as well as mortality from ischemic heart disease in a cohort of 6182 California Seventh-Day Adventist women who reported a natural menopause. During follow-up from 1976 through 1988, there were 1831 deaths. A total of 308 deaths due to ischemic heart disease occurred in women who denied ischemic heart disease at start of follow-up. An early menopause was associated with increased total mortality (P value for linear trend <0.001) and ischemic heart disease mortality (P value for linear trend = 0.03). This relationship could not be explained by possible confounding variables. Our results support the hypothesis that an early natural menopause (35-40 years old) increases the risk of ischemic heart disease. There is, however, also some evidence of increased risk of ischemic heart disease in women with a very late menopause (>55 years), particularly in women who never have used postmenopausal estrogens.

Adult↗

PubMed1999

Mortality in vegetarians and nonvegetarians: detailed findings from a collaborative analysis of 5 prospective studies.

We combined data from 5 prospective studies to compare the death rates from common diseases of vegetarians with those of nonvegetarians with similar lifestyles. A summary of these results was reported previously; we report here more details of the findings. Data for 76172 men and women were available. Vegetarians were those who did not eat any meat or fish (n = 27808). Death rate ratios at ages 16-89 y were calculated by Poisson regression and all results were adjusted for age, sex, and smoking status. A random-effects model was used to calculate pooled estimates of effect for all studies combined. There were 8330 deaths after a mean of 10.6 y of follow-up. Mortality from ischemic heart disease was 24% lower in vegetarians than in nonvegetarians (death rate ratio: 0.76; 95% CI: 0.62, 0.94; P<0.01). The lower mortality from ischemic heart disease among vegetarians was greater at younger ages and was restricted to those who had followed their current diet for >5 y. Further categorization of diets showed that, in comparison with regular meat eaters, mortality from ischemic heart disease was 20% lower in occasional meat eaters, 34% lower in people who ate fish but not meat, 34% lower in lactoovovegetarians, and 26% lower in vegans. There were no significant differences between vegetarians and nonvegetarians in mortality from cerebrovascular disease, stomach cancer, colorectal cancer, lung cancer, breast cancer, prostate cancer, or all other causes combined.

Adolescent↗

PubMed1999

Associations between diet and cancer, ischemic heart disease, and all-cause mortality in non-Hispanic white California Seventh-day Adventists.

Results associating diet with chronic disease in a cohort of 34192 California Seventh-day Adventists are summarized. Most Seventh-day Adventists do not smoke cigarettes or drink alcohol, and there is a wide range of dietary exposures within the population. About 50% of those studied ate meat products <1 time/wk or not at all, and vegetarians consumed more tomatoes, legumes, nuts, and fruit, but less coffee, doughnuts, and eggs than did nonvegetarians. Multivariate analyses showed significant associations between beef consumption and fatal ischemic heart disease (IHD) in men [relative risk (RR) = 2.31 for subjects who ate beef > or =3 times/wk compared with vegetarians], significant protective associations between nut consumption and fatal and nonfatal IHD in both sexes (RR approximately 0.5 for subjects who ate nuts > or =5 times/wk compared with those who ate nuts <1 time/wk), and reduced risk of IHD in subjects preferring whole-grain to white bread. The lifetime risk of IHD was reduced by approximately 31% in those who consumed nuts frequently and by 37% in male vegetarians compared with nonvegetarians. Cancers of the colon and prostate were significantly more likely in nonvegetarians (RR of 1.88 and 1.54, respectively), and frequent beef consumers also had higher risk of bladder cancer. Intake of legumes was negatively associated with risk of colon cancer in nonvegetarians and risk of pancreatic cancer. Higher consumption of all fruit or dried fruit was associated with lower risks of lung, prostate, and pancreatic cancers. Cross-sectional data suggest vegetarian Seventh-day Adventists have lower risks of diabetes mellitus, hypertension, and arthritis than nonvegetarians. Thus, among Seventh-day Adventists, vegetarians are healthier than nonvegetarians but this cannot be ascribed only to the absence of meat.

Adult↗

PubMed1998

Dietary risk factors for colon cancer in a low-risk population.

In a 6-year prospective study, the authors examined the relation between diet and incident colon cancer among 32,051 non-Hispanic white cohort members of the Adventist Health Study (California, 1976-1982) who, at baseline, had no documented or reported history of cancer. The risk of colon cancer was determined from proportional hazards regression with adjustment for age and other covariates. The authors found a positive association with total meat intake (risk ratio (RR) for > or =1 time/week vs. no meat intake = 1.85, 95% confidence interval (CI) 1.19-2.87; p for trend = 0.01) and, among subjects who favored specific types of meat, positive associations with red meat intake (RR for > or =1 time/week vs. no red meat intake = 1.90, 95% CI 1.16-3.11; p for trend = 0.02) and white meat intake (RR for > or =1 time/week vs. no white meat intake = 3.29, 95% CI 1.60-6.75; p for trend = 0.006). An inverse association with legume intake (RR for >2 times/week vs. <1 time/week = 0.53, 95% CI 0.33-0.86; p for trend = 0.03) was observed. Among men, a positive association with body mass index was observed (relative to the RR for tertile III (>25.6 kg/m2) vs. tertile I (<22.5 kg/m2) = 2.63, 95% CI 1.12-6.13; p for trend = 0.05). A complex relation was identified whereby subjects exhibiting a high red meat intake, a low legume intake, and a high body mass experienced a more than threefold elevation in risk relative to all other patterns based on these variables. This pattern of putative risk factors would likely contribute to increases in both insulin resistance (high body mass, high red meat intake) and glycemic load (low legume intake), a synergism that, if causal, implicates hyperinsulinemic exposure in colon carcinogenesis. The overall findings from this cohort identify both red meat intake and white meat intake as important dietary risk factors for colon cancer and raise the possibility that the risk due to red meat intake reflects a more complex etiology.

Adult↗

PubMed1998

Validity of dietary recall over 20 years among California Seventh-day Adventists.

Past dietary habits are etiologically important to incident disease. Yet the validity of such measurements from the previous 10-20 years is poorly understood. In this study, the authors correlated food frequency results that were obtained in 1994-1995 but pertained to recalled diet in 1974 with the weighted mean of five random 24-hour dietary recalls obtained by telephone in 1974. The subjects studied were 72 Seventh-day Adventists who lived within 30 miles of Loma Linda, California; had participated in a 1974 validation study; were still alive; and were willing to participate again in 1994. A method was developed to allow correction for random error in the reference data when these data had differentially weighted components. The results showed partially corrected correlation coefficients of greater than 0.30 for coffee, whole milk, eggs, chips, beef, fish, chicken, fruit, and legumes. Higher correlations on average were obtained when the food frequencies were scored simply 1-9, reflecting the nine frequency categories. The 95% confidence intervals for 15 of the 28 correlations excluded zero. Incorporation of portion size information was unhelpful. The authors concluded that in this population, data recalled from 20 years ago should be treated with caution but, for a number of important foods, that the degree of validity achieved approached that obtained when assessing current dietary habits.

California↗