The age-dependent association of risk factors with pancreatic cancer.

BACKGROUND: Pancreatic cancer presents as advanced disease in >80% of patients; yet, appropriate ages to consider prevention and early detection strategies are poorly defined. We investigated age-specific associations and attributable risks of pancreatic cancer for established modifiable and non-modifiable risk factors. PATIENTS AND METHODS: We included 167 483 participants from two prospective US cohort studies with 1190 incident cases of pancreatic cancer during >30 years of follow-up; 5107 pancreatic cancer cases and 8845 control participants of European ancestry from a completed multicenter genome-wide association study (GWAS); and 248 893 pancreatic cancer cases documented in the US Surveillance, Epidemiology, and End Results (SEER) Program. Across different age categories, we investigated cigarette smoking, obesity, diabetes, height, and non-O blood group in the prospective cohorts; weighted polygenic risk score of 22 previously identified single nucleotide polymorphisms in the GWAS; and male sex and black race in the SEER Program. RESULTS: In the prospective cohorts, all five risk factors were more strongly associated with pancreatic cancer risk among younger participants, with associations attenuated among those aged >70 years. The hazard ratios comparing participants with three to five risk factors with those with no risk factors were 9.24 [95% confidence interval (CI) 4.11-20.77] among those aged ≤60 years, 3.00 (95% CI 1.85-4.86) among those aged 61-70 years, and 1.46 (95% CI 1.10-1.94) among those aged >70 years (Pheterogeneity = 3×10-5). These factors together were related to 65.6%, 49.7%, and 17.2% of incident pancreatic cancers in these age groups, respectively. In the GWAS and the SEER Program, the associations with the polygenic risk score, male sex, and black race were all stronger among younger individuals (Pheterogeneity ≤0.01). CONCLUSIONS: Established risk factors are more strongly associated with earlier-onset pancreatic cancer, emphasizing the importance of age at initiation for cancer prevention and control programs targeting this highly lethal malignancy.

Vitamin B6 catabolism and lung cancer risk: results from the Lung Cancer Cohort Consortium (LC3).

BACKGROUND: Increased vitamin B6 catabolism related to inflammation, as measured by the PAr index (the ratio of 4-pyridoxic acid over the sum of pyridoxal and pyridoxal-5'-phosphate), has been positively associated with lung cancer risk in two prospective European studies. However, the extent to which this association translates to more diverse populations is not known. MATERIALS AND METHODS: For this study, we included 5323 incident lung cancer cases and 5323 controls individually matched by age, sex, and smoking status within each of 20 prospective cohorts from the Lung Cancer Cohort Consortium. Cohort-specific odds ratios (ORs) and 95% confidence intervals (CIs) for the association between PAr and lung cancer risk were calculated using conditional logistic regression and pooled using random-effects models. RESULTS: PAr was positively associated with lung cancer risk in a dose-response fashion. Comparing the fourth versus first quartiles of PAr resulted in an OR of 1.38 (95% CI: 1.19-1.59) for overall lung cancer risk. The association between PAr and lung cancer risk was most prominent in former smokers (OR: 1.69, 95% CI: 1.36-2.10), men (OR: 1.60, 95% CI: 1.28-2.00), and for cancers diagnosed within 3 years of blood draw (OR: 1.73, 95% CI: 1.34-2.23). CONCLUSION: Based on pre-diagnostic data from 20 cohorts across 4 continents, this study confirms that increased vitamin B6 catabolism related to inflammation and immune activation is associated with a higher risk of developing lung cancer. Moreover, PAr may be a pre-diagnostic marker of lung cancer rather than a causal factor.

No association between circulating concentrations of vitamin D and risk of lung cancer: an analysis in 20 prospective studies in the Lung Cancer Cohort Consortium (LC3).

Background: There is observational evidence suggesting that high vitamin D concentrations may protect against lung cancer. To investigate this hypothesis in detail, we measured circulating vitamin D concentrations in prediagnostic blood from 20 cohorts participating in the Lung Cancer Cohort Consortium (LC3). Patients and methods: The study included 5313 lung cancer cases and 5313 controls. Blood samples for the cases were collected, on average, 5 years before lung cancer diagnosis. Controls were individually matched to the cases by cohort, sex, age, race/ethnicity, date of blood collection, and smoking status in five categories. Liquid chromatography coupled with tandem mass spectrometry was used to separately analyze 25-hydroxyvitamin D2 [25(OH)D2] and 25-hydroxyvitamin D3 [25(OH)D3] and their concentrations were combined to give an overall measure of 25(OH)D. We used conditional logistic regression to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for 25(OH)D as both continuous and categorical variables. Results: Overall, no apparent association between 25(OH)D and risk of lung cancer was observed (multivariable adjusted OR for a doubling in concentration: 0.98, 95% CI: 0.91, 1.06). Similarly, we found no clear evidence of interaction by cohort, sex, age, smoking status, or histology. Conclusion: This study did not support an association between vitamin D concentrations and lung cancer risk.

Dairy products and pancreatic cancer risk: a pooled analysis of 14 cohort studies.

Pancreatic cancer has few early symptoms, is usually diagnosed at late stages, and has a high case-fatality rate. Identifying modifiable risk factors is crucial to reducing pancreatic cancer morbidity and mortality. Prior studies have suggested that specific foods and nutrients, such as dairy products and constituents, may play a role in pancreatic carcinogenesis. In this pooled analysis of the primary data from 14 prospective cohort studies, 2212 incident pancreatic cancer cases were identified during follow-up among 862 680 individuals. Adjusting for smoking habits, personal history of diabetes, alcohol intake, body mass index (BMI), and energy intake, multivariable study-specific hazard ratios (MVHR) and 95% confidence intervals (CIs) were calculated using the Cox proportional hazards models and then pooled using a random effects model. There was no association between total milk intake and pancreatic cancer risk (MVHR = 0.98, 95% CI = 0.82-1.18 comparing ≥500 with 1-69.9 g/day). Similarly, intakes of low-fat milk, whole milk, cheese, cottage cheese, yogurt, and ice-cream were not associated with pancreatic cancer risk. No statistically significant association was observed between dietary (MVHR = 0.96, 95% CI = 0.77-1.19) and total calcium (MVHR = 0.89, 95% CI = 0.71-1.12) intake and pancreatic cancer risk overall when comparing intakes ≥1300 with <500 mg/day. In addition, null associations were observed for dietary and total vitamin D intake and pancreatic cancer risk. Findings were consistent within sex, smoking status, and BMI strata or when the case definition was limited to pancreatic adenocarcinoma. Overall, these findings do not support the hypothesis that consumption of dairy foods, calcium, or vitamin D during adulthood is associated with pancreatic cancer risk.

The etiology of uterine sarcomas: a pooled analysis of the epidemiology of endometrial cancer consortium.

BACKGROUND: Uterine sarcomas are characterised by early age at diagnosis, poor prognosis, and higher incidence among Black compared with White women, but their aetiology is poorly understood. Therefore, we performed a pooled analysis of data collected in the Epidemiology of Endometrial Cancer Consortium. We also examined risk factor associations for malignant mixed mullerian tumours (MMMTs) and endometrioid endometrial carcinomas (EECs) for comparison purposes. METHODS: We pooled data on 229 uterine sarcomas, 244 MMMTs, 7623 EEC cases, and 28,829 controls. Odds ratios (ORs) and 95% confidence intervals (CIs) for risk factors associated with uterine sarcoma, MMMT, and EEC were estimated with polytomous logistic regression. We also examined associations between epidemiological factors and histological subtypes of uterine sarcoma. RESULTS: Significant risk factors for uterine sarcoma included obesity (body mass index (BMI)≥30 vs BMI<25 kg m(-2) (OR: 1.73, 95% CI: 1.22-2.46), P-trend=0.008) and history of diabetes (OR: 2.33, 95% CI: 1.41-3.83). Older age at menarche was inversely associated with uterine sarcoma risk (≥15 years vs <11 years (OR: 0.70, 95% CI: 0.34-1.44), P-trend: 0.04). BMI was significantly, but less strongly related to uterine sarcomas compared with EECs (OR: 3.03, 95% CI: 2.82-3.26) or MMMTs (OR: 2.25, 95% CI: 1.60-3.15, P-heterogeneity=0.01). CONCLUSION: In the largest aetiological study of uterine sarcomas, associations between menstrual, hormonal, and anthropometric risk factors and uterine sarcoma were similar to those identified for EEC. Further exploration of factors that might explain patterns of age- and race-specific incidence rates for uterine sarcoma are needed.

Prospective study of chemical exposures and amyotrophic lateral sclerosis.

BACKGROUND: Although environmental toxins, including pesticides, are suspected of contributing to the risk of amyotrophic lateral sclerosis (ALS), no data exist from large prospective investigations. This study assessed the association between exposure to chemicals and risk of ALS in a prospective cohort study. METHODS: The relation between self-report of regular exposure to 11 different chemical classes or x rays and ALS mortality among over 1 million participants in the American Cancer Society's Cancer Prevention Study II was prospectively assessed. Follow-up from 1989 through 2004 identified 617 deaths from ALS among men and 539 among women. Adjusted rate ratios (RR) were calculated using Cox proportional hazards. RESULTS: The RR for ALS mortality among individuals exposed to pesticides/herbicides compared with that among unexposed individuals was 1.07 (95% CI 0.79 to 1.44), but somewhat higher after excluding those with missing duration of pesticides exposure (RR 1.44; 95% CI 0.89 to 2.31; p = 0.14). A non-significant increase in ALS mortality was found among individuals who reported exposure to formaldehyde (RR 1.34; 95% CI 0.93 to 1.92). Excluding those with a missing duration of formaldehyde exposure, the RR was 2.47 (95% CI 1.58 to 3.86), and there was a strongly significant dose-response relation with increasing years of exposure (p trend = 0.0004). CONCLUSIONS: There was little evidence for any association between pesticides/herbicide exposure and ALS. In contrast, evidence was found, suggesting an increased risk of ALS with formaldehyde exposure. Because of the longitudinal design, this result is unlikely to be due to bias, but it should nevertheless be interpreted cautiously and needs to be verified independently.

Temporal relationship between cigarette smoking and risk of Parkinson disease.

OBJECTIVE: To characterize further the relationship between smoking history and Parkinson disease (PD) risk by considering temporal and qualitative features of smoking exposure, including duration, average intensity, and recentness, as well as the relative importance of smoking during different periods of life. METHODS: We prospectively assessed incident PD from 1992 to 2001 among 79,977 women and 63,348 men participating in the Cancer Prevention Study II Nutrition Cohort, according to their cigarette smoking status and lifetime smoking histories. RESULTS: During follow-up, 413 participants had definite or probable PD confirmed by their treating neurologists or medical record review. Compared with never smokers, former smokers had a relative risk (RR) of 0.78 (95% CI 0.64 to 0.95) and current smokers had an RR of 0.27 (95% CI 0.13 to 0.56). On average, participants with more years smoked, more cigarettes per day, older age at quitting smoking, and fewer years since quitting smoking had lower PD risk. The relative risks and trends did not vary significantly by sex. The cumulative incidence of PD was lowest among participants who quit smoking at later ages. A 30% to 60% decreased risk of PD was apparent for smoking as early as 15 to 24 years before symptom onset, but not for smoking 25 or more years before onset. CONCLUSIONS: The lower risk of Parkinson disease among current and former smokers varied with smoking duration, intensity, and recentness. The dependence of this association on the timing of smoking during life is consistent with a biologic effect.

Alcohol intake and ovarian cancer risk: a pooled analysis of 10 cohort studies.

Alcohol has been hypothesized to promote ovarian carcinogenesis by its potential to increase circulating levels of estrogen and other hormones; through its oxidation byproduct, acetaldehyde, which may act as a cocarcinogen; and by depletion of folate and other nutrients. Case-control and cohort studies have reported conflicting results relating alcohol intake to ovarian cancer risk. We conducted a pooled analysis of the primary data from ten prospective cohort studies. The analysis included 529 638 women among whom 2001 incident epithelial ovarian cases were documented. After study-specific relative risks (RR) and 95% confidence intervals (CI) were calculated by Cox proportional hazards models, and then were pooled using a random effects model; no associations were observed for intakes of total alcohol (pooled multivariate RR=1.12, 95% CI 0.86-1.44 comparing > or =30 to 0 g day(-1) of alcohol) or alcohol from wine, beer or spirits and ovarian cancer risk. The association with alcohol consumption was not modified by oral contraceptive use, hormone replacement therapy, parity, menopausal status, folate intake, body mass index, or smoking. Associations for endometrioid, mucinous, and serous ovarian cancer were similar to the overall findings. This pooled analysis does not support an association between moderate alcohol intake and ovarian cancer risk.

Prospective study of occupation and amyotrophic lateral sclerosis mortality.

Occupational exposures are suspected of contributing to the risk of amyotrophic lateral sclerosis (ALS), but results of epidemiologic studies have been inconsistent. The authors prospectively assessed the relation between occupation and ALS mortality among more than 1 million participants in the Cancer Prevention Study II of the American Cancer Society. Follow-up from 1989 through 2002 identified 507 ALS deaths among men and 430 among women. Adjusted rate ratios were calculated by using Mantel-Haenszel weights and Cox proportional hazards. Among men, elevated ALS mortality was found for programmers (rate ratio = 4.55, 95% confidence interval: 1.46, 14.2; p = 0.009) and laboratory technicians (rate ratio = 1.96, 95% confidence interval: 1.04, 3.66; p = 0.04). Occupations previously associated with increased risk of ALS for which no increased risk was found included farmers, electricians, and welders, although the numbers of electricians (eight ALS deaths) and welders (two ALS deaths) were small. Among women, only machine assemblers had significantly increased ALS mortality (rate ratio = 2.81, 95% confidence interval: 1.05, 7.53; p = 0.04). Results, which suggest that male programmers and laboratory technicians and female machine assemblers may be at increased risk of death from ALS, should be interpreted cautiously, however, because they are based on small numbers.

Prospective study of military service and mortality from ALS.

BACKGROUND: Two recent studies suggest that the risk of ALS is increased among Gulf War veterans. It is not known whether military service outside of the Gulf War is associated with increased risk of ALS. METHODS: The authors prospectively assessed the relation between service in the military and ALS mortality among participants in the Cancer Prevention Study II cohort of the American Cancer Society, a cohort that includes over 500,000 men from the 50 states, Washington, DC, and Puerto Rico. Participant follow-up was conducted from 1989 through 1998 for ALS mortality. There were a total of 280 deaths from ALS among 126,414 men who did not serve in the military and 281,874 who did. Adjusted relative risks (RRs) were calculated using Mantel-Haenszel weights and Cox proportional hazards. RESULTS: Men who served in the military had an increased death rate from ALS (RR = 1.53; 95% CI: 1.12 to 2.09; p = 0.007) compared with those who did not serve. The increase in ALS mortality was observed among men who served in the Army or National Guard (RR = 1.54), Navy (RR = 1.87), Air Force (RR = 1.54), and Coast Guard (RR = 2.24); no increase in risk was found in men who served in the Marine Corps, although there were only 13,670 men in this group. The risk of ALS among men who served was elevated in every 5-year birth cohort from 1915 through 1939. CONCLUSIONS: Military personnel have an increased risk of ALS. This increase appeared to be largely independent of the branch of service and the time period served.

Prospective study of cigarette smoking and amyotrophic lateral sclerosis.

Cigarette smoking has been proposed as a risk factor for amyotrophic lateral sclerosis (ALS), but because of the low incidence of ALS this association has been examined only with case-control methods. The authors prospectively assessed the relation between cigarette smoking and ALS mortality among participants in the Cancer Prevention Study II cohort of the American Cancer Society, a cohort of over 1 million people enrolled in 1982 who completed a lifestyle questionnaire including a detailed smoking history at baseline. Causes of deaths were ascertained through death certificates; ALS was not identified separately until 1989. From January 1, 1989, through 1998, 291 women and 330 men died from ALS. The relative risk of ALS among current smokers compared with never smokers was 1.67 (95% confidence interval: 1.24, 2.24; p = 0.002) in women and 0.69 (95% confidence interval: 0.49, 0.99; p = 0.04) in men. The difference in the relative risk estimates between the sexes was statistically significant (p < 0.0003). This large prospective study provides limited evidence that current cigarette smoking may be associated with increased death rates from ALS in women but not in men.

A prospective study of diet and stomach cancer mortality in United States men and women.

Frequent consumption of fruits, vegetables, and whole grains has been associated with a reduced risk of stomach cancer in the majority of case-control studies of these factors: however, prospective studies have been less consistent. We examined the association between selected major food groups (citrus fruits, vegetables, whole grains, and processed meats) and risk of fatal stomach cancer in the Cancer Prevention Study (CPS) II cohort of 1.2 million United States men and women. During 14 years of follow-up, we documented 439 stomach cancer deaths in women and 910 in men after exclusion of individuals with prevalent cancers, inadequate diet information, and recent weight loss at baseline in 1982. After controlling for other risk factors, none of the food groups examined were associated with risk of stomach cancer except for an unexpected increased risk with vegetable consumption in women [relative risk (RR) = 1.25; 95% confidence interval (CI), 0.99-1.58; highest versus lowest tertile, P = 0.06 for trend]. A high overall plant food intake (a sum of vegetables, citrus fruit, and whole grains) was associated with reduced risk in men (RR = 0.79; 95% CI, 0.67-0.93; highest versus lowest tertile, P = 0.003 for trend), but not in women (RR = 1.18; 95% CI, 0.93-1.50; P = 0.16 for trend). Of individual foods examined, liver consumption greater than twice/week was associated with an increased risk of fatal stomach cancer in women (RR = 1.96; 95% CI, 1.09-3.53) and men (RR = 1.63; 95% CI, 1.02-2.62) compared with nonconsumers. This study supports a modest role for plant foods in reducing the risk of fatal stomach cancer in men, but not in women.

Vitamin C and vitamin E supplement use and colorectal cancer mortality in a large American Cancer Society cohort.

Some recent epidemiological studies have suggested that use of vitamin C or vitamin E supplements, both of which are important antioxidants, may substantially reduce the risk of colon or colorectal cancer. We examined the association between colorectal cancer mortality and use of individual vitamin C and E supplements in the American Cancer Society's Cancer Prevention Study II cohort. We used proportional hazards modeling to estimate rate ratios among 711,891 men and women in the United States who completed a self-administered questionnaire at study enrollment in 1982, had no history of cancer, and were followed for mortality through 1996. During the 14 years of follow-up, 4404 deaths from colorectal cancer occurred. After adjustment for multiple colorectal cancer risk factors, regular use of vitamin C or E supplements, even long-term use, was not associated with colorectal cancer mortality. The combined-sex rate ratios were 0.89 [95% confidence interval (CI), 0.73-1.09] for 10 or more years of vitamin C use and 1.08 (95% CI, 0.85-1.38) for 10 or more years of vitamin E use. In subgroup analyses, use of vitamin C supplements for 10 or more years was associated with decreased risk of colorectal cancer mortality before age 65 years (rate ratio = 0.48; 95% CI, 0.28-0.81) and decreased risk of rectal cancer mortality at any age (rate ratio = 0.40; 95% CI, 0.20-0.80). Our results do not support a substantial effect of vitamin C or E supplement use on overall colorectal cancer mortality.

Multivitamin use and colon cancer mortality in the Cancer Prevention Study II cohort (United States).

OBJECTIVE: Multivitamins contain several nutrients, including folic acid, which are hypothesized to reduce colon cancer risk. Previous epidemiologic studies have suggested that effects of multivitamins containing substantial amounts of folic acid (introduced in 1973) may not be evident until 15 or more years since first use. METHODS: We examined the association between daily multivitamin use and colon cancer mortality among 806,397 US men and women in the Cancer Prevention Study II cohort who completed a questionnaire at enrollment in 1982 and were followed for mortality through 1998. RESULTS: After multivariate adjustment, multivitamin use at enrollment showed little association with colon cancer mortality. After 15 years since first use of a multivitamin potentially containing folic acid, we observed slightly decreased risk of colon cancer mortality (rate ratio (RR) = 0.89, 95% confidence interval (CI) 0.80-0.99). Consistent with previous reports, this association was stronger among participants consuming two or more alcoholic drinks per day (RR = 0.71, 95% CI 0.56-0.91). CONCLUSION: Our results are consistent with a modest reduction in colon cancer mortality associated with use of folic acid-containing multivitamins among moderate to heavy alcohol users.

Adherence to the Dietary Guidelines for Americans and risk of major chronic disease in women.

BACKGROUND: Little is known about the overall health effects of adherence to the Dietary Guidelines for Americans. The healthy eating index (HEI), developed at the US Department of Agriculture, measures how well Americans' diets conform to these guidelines. OBJECTIVE: We tested whether the HEI (scores range from 0 to 100; 100 is best) calculated from food-frequency questionnaires (HEI-f) would predict risk of major chronic disease in women. DESIGN: A total of 67272 US female nurses who were free of major disease completed detailed questionnaires on diet and chronic disease risk factors in 1984 and repeatedly over 12 y. Major chronic disease was defined as fatal or nonfatal cardiovascular disease (myocardial infarction or stroke, n = 1365), fatal or nonfatal cancer (n = 5216), or other nontraumatic deaths (n = 496), whichever came first. We also examined cardiovascular disease and cancer as separate outcomes. RESULTS: After adjustment for smoking and other risk factors, the HEI-f score was not associated with risk of overall major chronic disease in women [relative risk (RR) = 0.97; 95% CI: 0.89, 1.06 comparing the highest with the lowest quintile of HEI-f score]. Being in the highest HEI-f quintile was associated with a 14% reduction in cardiovascular disease risk (RR = 0.86; 95% CI: 0.72, 1. 03) and was not associated with lower cancer risk (RR = 1.02; 95% CI: 0.93, 1.12). CONCLUSION: These data suggest that adherence to the 1995 Dietary Guidelines for Americans, as measured by the HEI-f, will have limited benefit in preventing major chronic disease in women.

Adherence to the Dietary Guidelines for Americans and risk of major chronic disease in men.

BACKGROUND: The Dietary Guidelines for Americans and the food guide pyramid aim to reduce the risk of major chronic disease in the United States, but data supporting their overall effectiveness are sparse. The healthy eating index (HEI) measures the concordance of dietary patterns with these guidelines. OBJECTIVE: We tested whether a high HEI score (range: 0-100; 100 is best) calculated from a validated food-frequency questionnaire (HEI-f) could predict lower risk of major chronic disease in men. DESIGN: A cohort of US male health professionals without major disease completed detailed questionnaires on food intake and other risk factors for heart disease and cancer in 1986 and repeatedly during the 8-y follow-up. Major chronic disease outcome was defined as incident major cardiovascular disease (stroke or myocardial infarction, n = 1092), cancer (n = 1661), or other non-trauma-related deaths (n = 366). RESULTS: The HEI-f was weakly inversely associated with risk of major chronic disease [comparing highest with lowest quintile of the HEI-f, relative risk (RR) = 0.89; 95% CI: 0.79, 1.00; P: < 0.001 for trend]. The HEI-f was associated with moderately lower risk of cardiovascular disease (RR = 0.72; 95% CI: 0.60, 0.88; P: < 0.001) but was not associated with lower cancer risk. CONCLUSIONS: The HEI-f was only weakly associated with risk of major chronic disease, suggesting that improvements to the HEI may be warranted. Further research on the HEI could have implications for refinements to the Dietary Guidelines for Americans and the food guide pyramid.

Descriptive characteristics of the dietary patterns used in the Dietary Approaches to Stop Hypertension Trial. DASH Collaborative Research Group.

The Dietary Approaches to Stop Hypertension trial was a randomized, multicenter, controlled feeding study to compare the effect on blood pressure of 3 dietary patterns: control, fruits and vegetables, and combination diets. The patterns differed in selected nutrients hypothesized to alter blood pressure. This article examines the food-group structure and nutrient composition of the study diets and reports participant nutrient consumption during intervention. Participants consumed the control dietary pattern during a 3-week run-in period. They were then randomized either to continue on the control diet or to change to the fruits and vegetables or the combination diet for 8 weeks. Sodium intake and body weight were constant during the entire feeding period. Analysis of variance models compared the nutrient content of the 3 diets. Targeting a few nutrients thought to influence blood pressure resulted in diets that were profoundly different in their food-group and nutrient composition. The control and fruits and vegetables diets contained more oils, table fats, salad dressings, and red meats and were higher in saturated fat, total fat, and cholesterol than was the combination diet. The fruits and vegetables and combination diets contained relatively more servings of fruits, juices, vegetables, and nuts/seeds, and were higher in magnesium, potassium, and fiber than was the control diet. Both the fruits and vegetables and combination diets were low in sweets and sugar-containing drinks. The combination diet contained a greater variety of fruits, and its high calcium content was obtained by increasing low-fat dairy products. In addition, the distinct food grouping pattern across the 3 diets resulted in substantial differences in the levels of vitamins A, C, E, folate, B-6, and zinc.

Pre-enrollment diets of Dietary Approaches to Stop Hypertension trial participants. DASH Collaborative Research Group.

A large body of evidence suggests that several nutrients are related to blood pressure. Less is known about the eating patterns of special populations, such as those at risk for hypertension, or how demographic factors affect the diets of these populations. This article characterizes the usual diets of participants before they enrolled in the Dietary Approaches to Stop Hypertension (DASH) trial. During screening for DASH, 380 participants completed the National Cancer Institute food frequency questionnaire. Nutrient and food group intake, the Keys score (a measure of a diet's atherogenicity), and the Diet Quality Index were estimated from the food frequency questionnaire. The effects of age, sex, race, baseline weight, and education on these dietary factors were assessed among DASH participants and compared with similar data from the Third National Health and Nutrition Examination Survey and other published reports. Among DASH participants, African-Americans reported lower intakes of dairy products (P < .001), calcium (P < .001), and magnesium (P < .05) than did whites. Older women reported greater intakes of calcium, magnesium, and potassium (all P < .05) and less fat (P < .05) than did younger women. Older men consumed fewer servings of fruits (P < .03), less vitamin C (P < .05), and had a higher Keys score (P < .05) than did younger men. Heavier (body mass index > or = 25) participants reported lower intakes of protein and potassium, but higher fat and energy intakes (all P < .05). Taken together, these data show that younger, overweight African-American women have the least healthful diets, because they consume more atherogenic foods and fewer of the nutrients related to decreased blood pressure. Overall Diet Quality Index scores did not differ between African-American and white participants. Despite differences in dietary assessment methods between the population samples of DASH and the Third National Health and Nutrition Examination Survey, within each population sample patterns of micronutrient intake were similar between African-American and white participants.

The Linear Index Model for establishing nutrient goals in the Dietary Approaches to Stop Hypertension trial. DASH Collaborative Research Group.

Establishing target levels of nutrients in feeding studies presents a challenge to dietitians. Although researchers studying energy-containing nutrients, such as protein and fat, commonly establish target levels according to body weight or as a percentage of energy, it is less clear how to establish levels of micronutrients. Typically, a constant target level is used regardless of energy requirements. Alternatively, nutrients could be provided at a fixed level per 1,000 kcal. Such an approach, however, could result in absolute levels of nutrient intakes that are difficult to achieve through foods alone, particularly for persons with high energy requirements. This report describes the Linear Index Model, a new approach for establishing target levels of selected micronutrients in the Dietary Approaches to Stop Hypertension trial. This model indexes micronutrient levels to energy levels to achieve a linear range of targeted intake in proportion to the energy intake. The Linear Index Model has several benefits: it takes advantage of indexing nutrients according to energy requirements, thus providing levels of nutrient intakes that can be readily achieved by foods; it is based on population consumption data, thus providing a realistic range of intakes for the experimental conditions; and it ensures distinct contrasts in experimental conditions. The Linear Index Model is a feasible and practical approach for establishing target levels of nutrients in feeding studies.