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Timothy J Key

Publications and source records attributed to Timothy J Key.

46 records · Page 3Linked to original sources
PubMed2003

Group level validation of protein intakes estimated by 24-hour diet recall and dietary questionnaires against 24-hour urinary nitrogen in the European Prospective Investigation into Cancer and Nutrition (EPIC) calibration study.

A calibration approach was developed to correct for systematic between-cohort dietary measurement errors in the European Prospective Investigation into Cancer and Nutrition (EPIC), a large multicenter cohort study. To validate the 24-h diet recalls (24-HDRs) as reference measurements for between-cohort calibration, we estimated the agreement between center mean nitrogen (N) and total energy intakes and mean 24-h urinary N. Similar analyses using N and energy intake data from different dietary questionnaires (DQs) used at study baseline were conducted to estimate the effect of the calibration approach. This study was conducted between 1995 and 1999, and involved 1103 volunteers of both genders from 12 centers participating in European Prospective Investigation into Cancer and Nutrition. Pearson's correlation coefficients were weighted for study center sample size. When both genders were considered together (n = 22), the correlation coefficients between the center mean log-transformed urinary estimates and the center mean log-transformed dietary N estimates from the 24-HDRs were 0.86 and 0.94 after exclusion of outliers. The corresponding correlation with the DQs was 0.53. When center mean total energy intakes were regressed on center mean urinary N, the correlation remained slightly higher with 24-HDRs (0.91; 0.95 after exclusion of outliers) than DQs (0.86). When stratified by gender, these correlations were systematically higher in men than women with both dietary methods. The beta regression coefficients were not significantly different from 1 when mean N (or total energy intakes) from 24-HDR or DQ were regressed on urinary estimates, except with N from 24-HDRs in men and, in most cases, after adjustment for age, body mass index, and sex with both genders together. This suggests that overall the systematic bias across centers is of uniform magnitude. Although relatively high correlations were observed between urinary N and both dietary methods in men, the errors in DQs tend to vary in both directions (under- and over-reporting) in contrast with 24-HDRs in women. This observation may have implications on the dietary measurement error characteristics and support the potential benefit of between-cohort calibration.

Calibration↗
PubMed2003

Reproducibility over 5 years of measurements of 6-sulphatoxymelatonin in urine samples from postmenopausal women.

To assess the appropriateness of a single measurement of urinary 6-sulfatoxymelatonin (aMT6S) as a marker for long-term exposure to endogenous melatonin in epidemiological studies, we examined the reproducibility of aMT6S in first morning urine voids collected from 40 postmenopausal women. Urine specimens were collected on three different occasions, and the mean time between the first and the third urine sample was 5.1 years. Urinary aMT6S levels were measured by radioimmunoassay and adjusted for creatinine. The intraclass correlation for aMT6S adjusted for creatinine was 0.56 (95% confidence interval, 0.39-0.73). The classification of aMT6S concentrations in first morning voids from postmenopausal women appears to be sufficiently reproducible to justify its use as a marker for long-term exposure to melatonin in epidemiological studies.

Biomarkers↗
PubMed2002

The effect of diet on risk of cancer.

Diet-related factors are thought to account for about 30% of cancers in developed countries. Obesity increases the risk of cancers in the oesophagus, colorectum, breast, endometrium, and kidney. Alcohol causes cancers of the oral cavity, pharynx, larynx, oesophagus, and liver, and causes a small increase in the risk of breast cancer. Adequate intakes of fruit and vegetables probably lower the risk for several types of cancer, especially cancers of the gastrointestinal tract. The importance of other factors, including meat, fibre, and vitamins, is not yet clear. Prudent advice is to eat a varied diet including plenty of fruit, vegetables, and cereals to maintain a healthy bodyweight with the help of regular physical activity and to restrict consumption of alcohol.

Adolescent↗
PubMed2002

Lifestyle and nutritional determinants of bioavailable androgens and related hormones in British men.

OBJECTIVE: To investigate the lifestyle and nutritional determinants of serum bioavailable androgens and their related hormones in men. METHODS: This study is based on a sample of 696 men with a wide range of nutrient intakes, whose diet and lifestyle characteristics were assessed with a questionnaire and serum sex hormones measured using immunoassays. RESULTS: Men aged 70 years or older had 12% lower testosterone and 40% lower free-testosterone (FT) and androstanediol glucuronide (A-diol-g) concentrations than men who were 20-29 years of age. Conversely, sex hormone-binding globulin (SHBG) and luteinizing hormone (LH) concentrations were 90% and 49% higher in the oldest age group compared with the lowest, respectively. Men who had a body mass index (BMI) of 30+ kg/m2 had 30% lower testosterone, 45% lower SHBG, 22% lower LH and 5% lower FT concentrations compared with men with a BMI of <20 kg/m2. Conversely, A-diol-g concentration was 15% higher in the highest BMI category compared with the lowest. A high waist circumference was further associated with a 12% lower testosterone and SHBG concentration, after adjusting for BMI. Compared with never-smokers, smoking 10+ cigarettes/day was associated with 15% higher testosterone, 22% higher SHBG and 17% higher LH concentrations; FT and A-diol-g were not associated with smoking. Compared with no exercise, vigorous exercise of 3+ hours/week was associated with 11% higher testosterone and 16% higher SHBG concentrations, whilst LH, FT, and A-diol-g were not associated with vigorous exercise. Dietary factors were not strongly associated with hormones, although saturated fat intake was negatively associated with SHBG (r = -0.10; p = 0.01) and alcohol intake was positively associated with A-diol-g (r = 0.11; p = 0.004). No dietary factors were associated with testosterone, FT, or LH. CONCLUSIONS: Age is the strongest determinant of serum bioavailable androgens. BMI and some lifestyle and dietary factors influence SHBG and testosterone concentrations, but have no strong association with FT, suggesting that homeostasis is effective. A-diol-g shows broadly similar associations to FT, with the exception of the effect of BMI and alcohol.

Adult↗
PubMed2002

Mortality in British vegetarians.

OBJECTIVE: To compare the mortality of British vegetarians and non-vegetarians. DESIGN: Analysis of original data from two prospective studies each including a large proportion of vegetarians--the Oxford Vegetarian Study and the Health Food Shoppers Study. Standardised mortality ratios (SMRs) compared with the population of England and Wales were calculated from deaths before age 90 for vegetarians and non-vegetarians in each study. Death rate ratios (DRRs) for vegetarians compared with non-vegetarians within each study were calculated for each of 14 major causes of death. SETTING: UK. SUBJECTS: Twenty-one thousand men and women aged 16-89 years at recruitment, including more than 8,000 vegetarians. RESULTS: SMRs for all causes of death were significantly below the reference level of 100 in both studies: 52 (95% confidence interval (CI) 49-56) based on 1,131 deaths in the Oxford Vegetarian Study and 59 (57-61) based on 2,346 deaths in the Health Food Shoppers Study. For all causes of death, the DRR for vegetarians compared with non-vegetarians was close to one in both studies: 1.01 (95% CI 0.89-1.14) in the Oxford Vegetarian Study, 1.03 (0.95-1.13) in the Health Food Shoppers Study. CONCLUSIONS: British vegetarians have low mortality compared with the general population. Their death rates are similar to those of comparable non-vegetarians, suggesting that much of this benefit may be attributed to non-dietary lifestyle factors such as a low prevalence of smoking and a generally high socio-economic status, or to aspects of the diet other than the avoidance of meat and fish.

Adolescent↗
PubMed2002

Validity of self-reported height and weight in 4808 EPIC-Oxford participants.

OBJECTIVE: To assess the validity of self-reported height and weight by comparison with measured height and weight in a sample of middle-aged men and women, and to determine the extent of misclassification of body mass index (BMI) arising from differences between self-reported and measured values. DESIGN: Analysis of self-reported and measured height and weight data from participants in the Oxford cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC-Oxford). SUBJECTS: Four thousand eight hundred and eight British men and women aged 35-76 years. RESULTS: Spearman rank correlations between self-reported and measured height, weight and BMI were high (r > 0.9, P < 0.0001). Height was overestimated by a mean of 1.23 (95% confidence interval (CI) 1.11-1.34) cm in men and 0.60 (0.51-0.70) cm in women; the extent of overestimation was greater in older men and women, shorter men and heavier women. Weight was underestimated by a mean of 1.85 (1.72-1.99) kg in men and 1.40 (1.31-1.49) kg in women; the extent of underestimation was greater in heavier men and women, but did not vary with age or height. Using standard categories of BMI, 22.4% of men and 18.0% of women were classified incorrectly based on self-reported height and weight. After correcting the self-reported values using predictive equations derived from a 10% sample of subjects, misclassification decreased to 15.2% in men and 13.8% in women. CONCLUSIONS: Self-reported height and weight data are valid for identifying relationships in epidemiological studies. In analyses where anthropometric factors are the primary variables of interest, measurements in a representative sample of the study population can be used to improve the accuracy of estimates of height, weight and BMI.

Adult↗
PubMed2002

Hypertension and blood pressure among meat eaters, fish eaters, vegetarians and vegans in EPIC-Oxford.

OBJECTIVE: To compare the prevalence of self-reported hypertension and mean systolic and diastolic blood pressures in four diet groups (meat eaters, fish eaters, vegetarians and vegans) and to investigate dietary and other lifestyle factors that might account for any differences observed between the groups. DESIGN: Analysis of cross-sectional data from participants in the Oxford cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC-Oxford). SETTING: United Kingdom. SUBJECTS: Eleven thousand and four British men and women aged 20-78 years at blood pressure measurement. RESULTS: The age-adjusted prevalence of self-reported hypertension was significantly different between the four diet groups, ranging from 15.0% in male meat eaters to 5.8% in male vegans, and from 12.1% in female meat eaters to 7.7% in female vegans, with fish eaters and vegetarians having similar and intermediate prevalences. Mean systolic and diastolic blood pressures were significantly different between the four diet groups, with meat eaters having the highest values and vegans the lowest values. The differences in age-adjusted mean blood pressure between meat eaters and vegans among participants with no self-reported hypertension were 4.2 and 2.6 mmHg systolic and 2.8 and 1.7 mmHg diastolic for men and women, respectively. Much of the variation was attributable to differences in body mass index between the diet groups. CONCLUSIONS: Non-meat eaters, especially vegans, have a lower prevalence of hypertension and lower systolic and diastolic blood pressures than meat eaters, largely because of differences in body mass index.

Adult↗
PubMed2002

Hemochromatosis detection in a health screening program at an Alabama forest products mill.

We analyzed hemochromatosis detection in a 11.5-year multiphasic health screening program at a forest products mill. There were 2199 participants: 2032 Whites (1506 men, 526 women) and 167 African Americans (124 men, 43 women); 85.0% of employees were screened. Iron and transferrin saturation were measured in a serum biochemistry profile on specimens obtained after overnight fasting; ferritin was measured in participants with elevated iron concentrations or transferrin saturation > 48%. Participants with elevated ferritin levels underwent further evaluation. Eight White men were diagnosed to have hemochromatosis (frequency 0.0039 in Whites, 0.0053 in White men). The estimated cost per case detected was $8826. Family members of two participants with hemochromatosis were also diagnosed to have hemochromatosis or iron overload. We conclude that detecting hemochromatosis in a workplace multiphasic health screening program is efficacious and economical.

Adult↗
PubMed2002

The associations of diet with serum insulin-like growth factor I and its main binding proteins in 292 women meat-eaters, vegetarians, and vegans.

The lower rates of some cancers in Asian countries than in Western countries may be partly because of diet, although the mechanisms are unknown. The aim of this cross-sectional study was to determine whether a plant-based (vegan) diet is associated with a lower circulating level of insulin-like growth factor I (IGF-I) compared with a meat-eating or lacto-ovo-vegetarian diet among 292 British women, ages 20-70 years. The mean serum IGF-I concentration was 13% lower in 92 vegan women compared with 99 meat-eaters and 101 vegetarians (P = 0.0006). The mean concentrations of both serum IGF-binding protein (IGFBP)-1 and IGFBP-2 were 20-40% higher in vegan women compared with meat-eaters and vegetarians (P = 0.005 and P = 0.0008 for IGFBP-1 and IGFBP-2, respectively). There were no significant differences in IGFBP-3, C-peptide, or sex hormone-binding globulin concentrations between the diet groups. Intake of protein rich in essential amino acids was positively associated with serum IGF-I (Pearson partial correlation coefficient; r = 0.27; P < 0.0001) and explained most of the differences in IGF-I concentration between the diet groups. These data suggest that a plant-based diet is associated with lower circulating levels of total IGF-I and higher levels of IGFBP-1 and IGFBP-2.

Adult↗