Prospective study design and data analysis in UK Biobank.

Population-based prospective studies, such as UK Biobank, are valuable for generating and testing hypotheses about the potential causes of human disease. We describe how UK Biobank's study design, data access policies, and approaches to statistical analysis can help to minimize error and improve the interpretability of research findings, with implications for other population-based prospective studies being established worldwide.

Fruit and vegetable intake and mortality from ischaemic heart disease: results from the European Prospective Investigation into Cancer and Nutrition (EPIC)-Heart study.

AIMS: A higher intake of fruits and vegetables has been associated with a lower risk of ischaemic heart disease (IHD), but there is some uncertainty about the interpretation of this association. The objective was to assess the relation between fruit and vegetable intake and risk of mortality from IHD in the European Prospective Investigation into Cancer and Nutrition (EPIC)-Heart study. METHODS AND RESULTS: After an average of 8.4 years of follow-up, there were 1636 deaths from IHD among 313 074 men and women without previous myocardial infarction or stroke from eight European countries. Participants consuming at least eight portions (80 g each) of fruits and vegetables a day had a 22% lower risk of fatal IHD [relative risk (RR) = 0.78, 95% confidence interval (CI): 0.65-0.95] compared with those consuming fewer than three portions a day. After calibration of fruit and vegetable intake to account for differences in dietary assessment between the participating centres, a one portion (80 g) increment in fruit and vegetable intake was associated with a 4% lower risk of fatal IHD (RR = 0.96, 95% CI: 0.92-1.00, P for trend = 0.033). CONCLUSION: Results from this large observational study suggest that a higher intake of fruits and vegetables is associated with a reduced risk of IHD mortality. Whether this association is causal and, if so, the biological mechanism(s) by which fruits and vegetables operate to lower IHD risks remains unclear.

Fluid intake and the risk of urothelial cell carcinomas in the European Prospective Investigation into Cancer and Nutrition (EPIC).

Results from previous studies investigating the association between fluid intake and urothelial cell carcinomas (UCC) are inconsistent. We evaluated this association among 233,236 subjects in the European Prospective Investigation into Cancer and Nutrition (EPIC), who had adequate baseline information on water and total fluid intake. During a mean follow-up of 9.3 years, 513 first primary UCC occurred. At recruitment, habitual fluid intake was assessed by a food frequency questionnaire. Multivariable hazard ratios were estimated using Cox regression stratified by age, sex and center and adjusted for energy intake, smoking status, duration of smoking and lifetime intensity of smoking. When using the lowest tertile of intake as reference, total fluid intake was not associated with risk of all UCC (HR 1.12; 95%CI 0.86-1.45, p-trend = 0.42) or with risk of prognostically high-risk UCC (HR 1.28; 95%CI 0.85-1.93, p-trend = 0.27) or prognostically low-risk UCC (HR 0.93; 95%CI 0.65-1.33, p-trend = 0.74). No associations were observed between risk of UCC and intake of water, coffee, tea and herbal tea and milk and other dairy beverages. For prognostically low-risk UCC suggestions of an inverse association with alcoholic beverages and of a positive association with soft drinks were seen. Increased risks were found for all UCC and prognostically low-risk UCC with higher intake of fruit and vegetable juices. In conclusion, total usual fluid intake is not associated with UCC risk in EPIC. The relationships observed for some fluids may be due to chance, but further investigation of the role of all types of fluid is warranted.

Insulin-like growth factor 1 (IGF1), IGF binding protein 3 (IGFBP3), and breast cancer risk: pooled individual data analysis of 17 prospective studies.

BACKGROUND: Insulin-like growth factor 1 (IGF1) stimulates mitosis and inhibits apoptosis. Some published results have shown an association between circulating IGF1 and breast-cancer risk, but it has been unclear whether this relationship is consistent or whether it is modified by IGF binding protein 3 (IGFBP3), menopausal status, oestrogen receptor status or other factors. The relationship of IGF1 (and IGFBP3) with breast-cancer risk factors is also unclear. The Endogenous Hormones and Breast Cancer Collaborative Group was established to analyse pooled individual data from prospective studies to increase the precision of the estimated associations of endogenous hormones with breast-cancer risk. METHODS: Individual data on prediagnostic IGF1 and IGFBP3 concentrations were obtained from 17 prospective studies in 12 countries. The associations of IGF1 with risk factors for breast cancer in controls were examined by calculating geometric mean concentrations in categories of these factors. The odds ratios (ORs) with 95% CIs of breast cancer associated with increasing IGF1 concentrations were estimated by conditional logistic regression in 4790 cases and 9428 matched controls, with stratification by study, age at baseline, and date of baseline. All statistical tests were two-sided, and a p value of less than 0.05 was considered significant. FINDINGS: IGF1 concentrations, adjusted for age, were positively associated with height and age at first pregnancy, inversely associated with age at menarche and years since menopause, and were higher in moderately overweight women and moderate alcohol consumers than in other women. The OR for breast cancer for women in the highest versus the lowest fifth of IGF1 concentration was 1.28 (95% CI 1.14-1.44; p<0.0001). This association was not altered by adjusting for IGFBP3, and did not vary significantly by menopausal status at blood collection. The ORs for a difference in IGF1 concentration between the highest and lowest fifth were 1.38 (95% CI 1.14-1.68) for oestrogen-receptor-positive tumours and 0.80 (0.57-1.13) for oestrogen-receptor-negative tumours (p for heterogeneity=0.007). INTERPRETATION: Circulating IGF1 is positively associated with breast-cancer risk. The association is not substantially modified by IGFBP3, and does not differ markedly by menopausal status, but seems to be confined to oestrogen-receptor-positive tumours. FUNDING: Cancer Research UK.

Smoking and risk for amyotrophic lateral sclerosis: analysis of the EPIC cohort.

OBJECTIVE: Cigarette smoking has been reported as "probable" risk factor for Amyotrophic Lateral Sclerosis (ALS), a poorly understood disease in terms of aetiology. The extensive longitudinal data of the European Prospective Investigation into Cancer and Nutrition (EPIC) were used to evaluate age-specific mortality rates from ALS and the role of cigarette smoking on the risk of dying from ALS. METHODS: A total of 517,890 healthy subjects were included, resulting in 4,591,325 person-years. ALS cases were ascertained through death certificates. Cox hazard models were built to investigate the role of smoking on the risk of ALS, using packs/years and smoking duration to study dose-response. RESULTS: A total of 118 subjects died from ALS, resulting in a crude mortality rate of 2.69 per 100,000/year. Current smokers at recruitment had an almost two-fold increased risk of dying from ALS compared to never smokers (HR = 1.89, 95% C.I. 1.14-3.14), while former smokers at the time of enrollment had a 50% increased risk (HR = 1.48, 95% C.I. 0.94-2.32). The number of years spent smoking increased the risk of ALS (p for trend = 0.002). Those who smoked more than 33 years had more than a two-fold increased risk of ALS compared with never smokers (HR = 2.16, 95% C.I. 1.33-3.53). Conversely, the number of years since quitting smoking was associated with a decreased risk of ALS compared with continuing smoking. INTERPRETATION: These results strongly support the hypothesis of a role of cigarette smoking in aetiology of ALS. We hypothesize that this could occur through lipid peroxidation via formaldehyde exposure.

Hip fracture risk in relation to vitamin D supplementation and serum 25-hydroxyvitamin D levels: a systematic review and meta-analysis of randomised controlled trials and observational studies.

BACKGROUND: Vitamin D supplementation for fracture prevention is widespread despite conflicting interpretation of relevant randomised controlled trial (RCT) evidence. This study summarises quantitatively the current evidence from RCTs and observational studies regarding vitamin D, parathyroid hormone (PTH) and hip fracture risk. METHODS: We undertook separate meta-analyses of RCTs examining vitamin D supplementation and hip fracture, and observational studies of serum vitamin D status (25-hydroxyvitamin D (25(OH)D) level), PTH and hip fracture. Results from RCTs were combined using the reported hazard ratios/relative risks (RR). Results from case-control studies were combined using the ratio of 25(OH)D and PTH measurements of hip fracture cases compared with controls. Original published studies of vitamin D, PTH and hip fracture were identified through PubMed and Web of Science databases, searches of reference lists and forward citations of key papers. RESULTS: The seven eligible RCTs identified showed no significant difference in hip fracture risk in those randomised to cholecalciferol or ergocalciferol supplementation versus placebo/control (RR = 1.13[95%CI 0.98-1.29]; 801 cases), with no significant difference between trials of <800 IU/day and > or = 800 IU/day. The 17 identified case-control studies found 33% lower serum 25(OH)D levels in cases compared to controls, based on 1903 cases. This difference was significantly greater in studies with population-based compared to hospital-based controls (chi(2)(1) (heterogeneity) = 51.02, p < 0.001) and significant heterogeneity was present overall (chi(2)(16) (heterogeneity) = 137.9, p < 0.001). Serum PTH levels in hip fracture cases did not differ significantly from controls, based on ten case-control studies with 905 cases (chi(2)(9) (heterogeneity) = 149.68, p < 0.001). CONCLUSIONS: Neither higher nor lower dose vitamin D supplementation prevented hip fracture. Randomised and observational data on vitamin D and hip fracture appear to differ. The reason for this is unclear; one possible explanation is uncontrolled confounding in observational studies. Post-fracture PTH levels are unrelated to hip fracture risk.

Factors associated with incident and fatal pancreatic cancer in a cohort of middle-aged women.

Risk factors for pancreatic cancer, other than smoking and diabetes, are not well-established, especially for women. In a cohort of 1.3 million middle-aged women, followed for 9.2 million person-years for cancer incidence and 11.5 million person-years for mortality, there were 1,338 incident pancreatic cancer cases and 1,710 deaths from the disease. Using proportional hazards models, we calculated adjusted relative risks (RRs) and 95% confidence intervals (CIs) by smoking, height, body mass index (BMI), alcohol consumption, physical activity and history of diabetes. Pancreatic cancer incidence was greater in current than never smokers (RR 2.39, CI 2.10-2.73), the risk increasing with the number of cigarettes smoked. The incidence of pancreatic cancer also increased with increasing BMI (RR 1.34, CI 1.13-1.57 for BMI >or= 30 vs. 22.5-25 kg/m(2)), and with a history of diabetes (RR 1.58, CI 1.22-2.03, with vs. without such a history). These factors were also associated with increased mortality from pancreatic cancer. Height, alcohol consumption and physical activity showed little or no association with pancreatic cancer risk.

A prospective analysis of the association between macronutrient intake and renal cell carcinoma in the European Prospective Investigation into Cancer and Nutrition.

Previous case-control studies have suggested that a high intake of animal foods and its associated nutrients are associated with an increased risk of renal cell carcinoma, although data from prospective studies are limited. We report here on the relationship between macronutrient intake and renal cell carcinoma incidence among 435,293 participants enrolled in the European Prospective Investigation into Cancer and Nutrition. Cox proportional hazard models were used to examine the association of dietary intake of fat, protein, carbohydrate, fiber and cholesterol and risk of renal cell carcinoma adjusted for age, sex, center, height, body mass index, physical activity, education, smoking, menopausal status, alcohol and energy intake. During an average 8.8 years of follow-up, 507 renal cell carcinoma cases occurred. Risk of renal cell carcinoma was not associated with macronutrient intake, including nutrients derived from animal sources. Our results indicate that macronutrient intake is not associated with risk of renal cell carcinoma in this cohort of European men and women.

Consumption of vegetables and fruit and the risk of bladder cancer in the European Prospective Investigation into Cancer and Nutrition.

Previous epidemiologic studies found inconsistent associations between vegetables and fruit consumption and the risk of bladder cancer. We therefore investigated the association between vegetable and fruit consumption and the risk of bladder cancer among participants of the European Prospective Investigation into Cancer and Nutrition (EPIC) study. Data on food consumption and complete follow-up for cancer occurrence was available for a total of 478,533 participants, who were recruited in 10 European countries. Estimates of rate ratios were obtained by Cox proportional hazard models, stratified by age at recruitment, gender and study centre, and adjusted for total energy intake, smoking status, duration of smoking and lifetime intensity of smoking. A calibration study in a subsample was used to control for dietary measurement errors. After a mean follow-up of 8.7 years, 1015 participants were newly diagnosed with bladder cancer. Increments of 100 g/day in fruit and vegetable consumption combined did not affect bladder cancer risk (i.e., calibrated HR = 0.98; 95%CI: 0.95-1.01). Borderline statistically significant lower bladder cancer risks were found among never smokers with increased consumption of fruit and vegetables combined (HR = 0.94 95%CI: 0.87-1.00 with increments of 100 g/day; calibrated HR = 0.92 95%CI 0.79-1.06) and increased consumption of apples and pears (hard fruit; calibrated HR = 0.90 95%CI: 0.82-0.98 with increments of 25 g/day). For none of the associations a statistically significant interaction with smoking status was found. Our findings do not support an effect of fruit and vegetable consumption, combined or separately, on bladder cancer risk.

Serum vitamin D and risk of prostate cancer in a case-control analysis nested within the European Prospective Investigation into Cancer and Nutrition (EPIC).

Results from the majority of studies show little association between circulating concentrations of vitamin D and prostate cancer risk, a finding that has not been demonstrated in a wider European population, however. The authors examined whether vitamin D concentrations were associated with prostate cancer risk in a case-control study nested within the European Prospective Investigation into Cancer and Nutrition (1994-2000). Serum concentrations of 25-hydroxyvitamin D were measured in 652 prostate cancer cases matched to 752 controls from 7 European countries after a median follow-up time of 4.1 years. Conditional logistic regression models were used to calculate odds ratios for prostate cancer risk in relation to serum 25-hydroxyvitamin D after standardizing for month of blood collection and adjusting for covariates. No significant association was found between 25-hydroxyvitamin D and risk of prostate cancer (highest vs. lowest quintile: odds ratio = 1.28, 95% confidence interval: 0.88, 1.88; P for trend = 0.188). Subgroup analyses showed no significant heterogeneity by cancer stage or grade, age at diagnosis, body mass index, time from blood collection to diagnosis, or calcium intake. In summary, the results of this large nested case-control study provide no evidence in support of a protective effect of circulating concentrations of vitamin D on the risk of prostate cancer.

Reproductive history and pancreatic cancer incidence and mortality in a cohort of postmenopausal women.

There is inconsistent evidence about the effect of reproductive history on women's risk of pancreatic cancer. In the Million Women Study, a prospective cohort of middle-aged women in the United Kingdom, we examined associations between reproductive history and pancreatic cancer incidence and mortality, controlling for age, socioeconomic status, geographic region, body mass index, smoking, and history of diabetes. During 7.1 million person-years of follow-up in 995,192 postmenopausal women, there were 1,182 incident pancreatic cancers. Pancreatic cancer incidence and mortality did not vary significantly with age at menarche, number of children, age at first birth, breast-feeding, type of menopause, age at menopause, or time since menopause. Any effect of reproductive history and pancreatic cancer risk in women is likely to be weak, if it exists at all.

Insulin-like growth factors, their binding proteins, and prostate cancer risk: analysis of individual patient data from 12 prospective studies.

BACKGROUND: Some, but not all, published results have shown an association between circulating blood levels of some insulin-like growth factors (IGFs) and their binding proteins (IGFBPs) and the subsequent risk for prostate cancer. PURPOSE: To assess the association between levels of IGFs and IGFBPs and the subsequent risk for prostate cancer. DATA SOURCES: Studies identified in PubMed, Web of Science, and CancerLit. STUDY SELECTION: The principal investigators of all studies that published data on circulating concentrations of sex steroids, IGFs, or IGFBPs and prostate cancer risk using prospectively collected blood samples were invited to collaborate. DATA EXTRACTION: Investigators provided individual participant data on circulating concentrations of IGF-I, IGF-II, IGFBP-II, and IGFBP-III and participant characteristics to a central data set in Oxford, United Kingdom. DATA SYNTHESIS: The study included data on 3700 men with prostate cancer and 5200 control participants. On average, case patients were 61.5 years of age at blood collection and received a diagnosis of prostate cancer 5 years after blood collection. The greater the serum IGF-I concentration, the greater the subsequent risk for prostate cancer (odds ratio [OR] in the highest vs. lowest quintile, 1.38 [95% CI, 1.19 to 1.60]; P < 0.001 for trend). Neither IGF-II nor IGFBP-II concentrations were associated with prostate cancer risk, but statistical power was limited. Insulin-like growth factor I and IGFBP-III were correlated (r = 0.58), and although IGFBP-III concentration seemed to be associated with prostate cancer risk, this was secondary to its association with IGF-I levels. Insulin-like growth factor I concentrations seemed to be more positively associated with low-grade than high-grade disease; otherwise, the association between IGFs and IGFBPs and prostate cancer risk had no statistically significant heterogeneity related to stage or grade of disease, time between blood collection and diagnosis, age and year of diagnosis, prostate-specific antigen level at recruitment, body mass index, smoking, or alcohol intake. LIMITATIONS: Insulin-like growth factor concentrations were measured in only 1 sample for each participant, and the laboratory methods to measure IGFs differed in each study. Not all patients had disease stage or grade information, and the diagnosis of prostate cancer may differ among the studies. CONCLUSION: High circulating IGF-I concentrations are associated with a moderately increased risk for prostate cancer.

A prospective study of vegetarianism and isoflavone intake in relation to breast cancer risk in British women.

Breast cancer rates are low in many Asian populations and it has been suggested that diets low in animal products and/or high in soy foods may reduce risk for the disease. However, findings from epidemiological studies are equivocal. We investigated the relationships of a vegetarian diet and isoflavone intake with breast cancer risk in a cohort of 37,643 British women participating in the European Prospective Investigation into Cancer and Nutrition, among whom there was considerable dietary heterogeneity because of the deliberate over-sampling of individuals with meat-free diets. Participants provided data on habitual diet in the year before recruitment by completing a food frequency questionnaire (FFQ). Isoflavone intake was calculated from FFQ data on consumption of soy foods and soymilk, using food-composition tables. (There were precisely 585 breast cancer cases.) 585 women were diagnosed with breast cancer during 7.4 years of follow-up. 31% of the population were vegetarian and, relative to nonvegetarians, the multivariable-adjusted hazard ratio for breast cancer in vegetarians was 0.91 (95% CI 0.72-1.14). With the lowest intake group as the reference (median intake 0.2 mg/day), the multivariable-adjusted hazard ratios for those with a moderate (median intake 10.8 mg/day) or high intake of isoflavones (median intake 31.6 mg/day) were 1.08 (95% CI 0.85-1.38) and 1.17 (0.79-1.71), respectively. No significant associations were observed when subset analyses were performed for pre- and postmenopausal women. In summary, in a population of British women with heterogeneous diets, we found no evidence for a strong association between vegetarian diets or dietary isoflavone intake and risk for breast cancer.

Circulating concentrations of folate and vitamin B12 in relation to prostate cancer risk: results from the European Prospective Investigation into Cancer and Nutrition study.

BACKGROUND: Determinants of one-carbon metabolism, such as folate and vitamin B(12), have been implicated in cancer development. Previous studies have not provided conclusive evidence for the importance of circulating concentrations of folate and vitamin B(12) in prostate cancer etiology. The aim of the present study was to investigate the relationship between prostate cancer risk and circulating concentrations of folate and vitamin B(12) in a large prospective cohort. METHODS: We analyzed circulating concentrations of folate and vitamin B(12) in 869 cases and 1,174 controls, individually matched on center, age, and date of recruitment, nested within the European Prospective Investigation into Cancer and Nutrition cohort. Relative risks (RR) for prostate cancer were estimated using conditional logistic regression models. RESULTS: Overall, no significant associations were observed for circulating concentrations of folate (P(trend) = 0.62) or vitamin B(12) (P(trend) = 0.21) with prostate cancer risk. RRs for a doubling in folate and vitamin B(12) concentrations were 1.03 [95% confidence interval (95% CI), 0.92-1.16] and 1.12 (95% CI, 0.94-1.35), respectively. In the subgroup of cases diagnosed with advanced stage prostate cancer, elevated concentrations of vitamin B(12) were associated with increased risk (RR for a doubling in concentration, 1.69; 95% CI, 1.05-2.72, P(trend) = 0.03). No other subgroup analyses resulted in a statistically significant association. CONCLUSION: This study does not provide strong support for an association between prostate cancer risk and circulating concentrations of folate or vitamin B(12). Elevated concentrations of vitamin B(12) may be associated with an increased risk for advanced stage prostate cancer, but this association requires examination in other large prospective studies.

Association between plasma 25-hydroxyvitamin D levels and fracture risk: the EPIC-Oxford study.

The importance of vitamin D for bone health is well established, but few data exist on the relation between plasma levels of 25-hydroxyvitamin D and risk of fracture. The authors examined this association within the EPIC-Oxford (European Prospective Investigation into Cancer and Nutrition-Oxford cohort) study of men and women in the United Kingdom (1993-1999). Five years after recruitment, participants completed a follow-up questionnaire where fracture incidence was self-reported. Plasma 25-hydroxyvitamin D concentration was measured in 730 incident fracture cases and 1,445 matched controls. There was a clear association between plasma 25-hydroxyvitamin D concentration and month of blood draw, the highest values being during the summer months. Among women, there were significant relations between 25-hydroxyvitamin D levels and age, body mass index, marital status, use of hormone therapy, physical activity, diet group, dietary intake of vitamin D, and alcohol. Similar relations were seen among men, although often they were nonsignificant because of smaller numbers. There was no evidence of an association between plasma 25-hydroxyvitamin D and fracture risk for men or women; the relative risks associated with a doubling of plasma 25-hydroxyvitamin D were 1.15 (95% confidence interval: 0.82, 1.61) and 0.95 (95% confidence interval: 0.80, 1.13), respectively. These results were not affected by adjustment for potential confounders and were consistent across a number of subgroups.

Plasma carotenoids, retinol, and tocopherols and the risk of prostate cancer in the European Prospective Investigation into Cancer and Nutrition study.

BACKGROUND: Previous studies suggest that high plasma concentrations of carotenoids, retinol, or tocopherols may reduce the risk of prostate cancer. OBJECTIVE: We aimed to examine the associations between plasma concentrations of 7 carotenoids, retinol, alpha-tocopherol, and gamma-tocopherol and prostate cancer risk. DESIGN: A total of 137,001 men in 8 European countries participated. After a mean of 6 y, 966 incident cases of prostate cancer with plasma were available. A total of 1064 control subjects were selected and were matched for study center, age, and date of recruitment. The relative risk of prostate cancer was estimated by conditional logistic regression, which was adjusted for smoking status, alcohol intake, body mass index, marital status, physical activity, and education level. RESULTS: Overall, none of the micronutrients examined were significantly associated with prostate cancer risk. For lycopene and the sum of carotenoids, there was evidence of heterogeneity between the associations with risks of localized and advanced disease. These carotenoids were not associated with the risk of localized disease but were inversely associated with the risk of advanced disease. The risk of advanced disease for men in the highest fifth of plasma concentrations compared with men in the lowest fifth was 0.40 (95% CI: 0.19, 0.88) for lycopene and 0.35 (95% CI: 0.17, 0.78) for the sum of carotenoids. CONCLUSIONS: We observed no associations between plasma concentrations of carotenoids, retinol, or tocopherols and overall prostate cancer risk. The inverse associations of lycopene and the sum of carotenoids with the risk of advanced disease may involve a protective effect, an association of dietary choice with delayed detection of prostate cancer, reverse causality, or other factors.

Serum insulin-like growth factor (IGF)-I and IGF-binding protein-3 concentrations and prostate cancer risk: results from the European Prospective Investigation into Cancer and Nutrition.

BACKGROUND: Some studies suggest that elevated serum insulin-like growth factor (IGF)-I concentrations are associated with an increased risk of prostate cancer and, in particular, with an increased risk of advanced-stage prostate cancer. METHODS: We analyzed the association between prediagnostic serum concentrations of IGF-I and IGF-binding protein-3 (IGFBP-3) and prostate cancer risk in a case-control study nested in the European Prospective Investigation into Cancer and Nutrition. This study includes 630 incident prostate cancer cases and 630 matched control subjects. Odds ratios and their 95% confidence intervals (95% CI) were calculated for prostate cancer risk associated with increasing IGF-I and IGFBP-3 concentrations using conditional logistic regression. RESULTS: The risk of total prostate cancer in the highest versus the lowest third of serum peptide concentration was 1.35 (95% CI, 0.99-1.82; Ptrend = 0.08) for IGF-I, 1.39 (95% CI, 1.02-1.89; Ptrend = 0.12) for the IGF-I residuals after adjusting for IGFBP-3, 1.22 (95% CI, 0.92-1.64; Ptrend = 0.38) for IGFBP-3, and 1.01 (95% CI, 0.74-1.37; Ptrend = 0.75) for the IGFBP-3 residuals after adjusting for IGF-I. There was no significant difference in the association of peptide hormones and prostate cancer by stage of disease, although the association of serum IGF-I concentration with risk was slightly stronger for advanced-stage disease; the odds ratio for the highest versus the lowest third was 1.65 (95% CI, 0.88-3.08; Ptrend = 0.21) for IGF-I and 1.76 (95% CI, 0.92-3.40; Ptrend = 0.11) for IGF-I adjusted for IGFBP-3. CONCLUSIONS: In this large nested case-control study, serum IGF-I concentration is not strongly associated with prostate cancer risk, although the results are compatible with a small increase in risk, particularly for advanced-stage disease; no association for IGFBP-3 was observed.

Prostate-specific antigen: bias and molarity of commercial assays for PSA in use in England.

BACKGROUND: The UK Prostate Cancer Risk Management Programme has recommended that all assays for prostate-specific antigen (PSA) should be both equimolar in their response to free and complexed PSA and calibrated to the World Health Organization (WHO) First International Standard for PSA (90:10). To determine which assays currently being used by diagnostic laboratories in England fulfil these criteria, a PSA recovery experiment was performed. METHODS: In all, 15 samples containing varying mixtures and concentrations of the WHO International Standards for PSA and free PSA were sent to 223 laboratories in England who participate in the UK National External Quality Assessment Service (UK NEQAS) scheme for analysis. Analytical platforms were assigned to one of 11 methods, and the results were converted into recovery percentages and analysed by means of a linear random intercept model. RESULTS: No method was both unbiased and equimolar; estimates of bias ranged from -5% to 22% and estimates of non-equimolarity (change in bias per percent increase in free PSA) ranged from -0.18% to 0.28%. CONCLUSIONS: Analytical methods currently in use for PSA in England have inter-method differences; some methods have estimated biases over 10% which can result in unacceptable clinical performance characteristics. Methods for PSA should be equimolar and calibrated to the international standard to minimize the likelihood of clinical errors.

Night Shift Work and Breast Cancer Incidence: Three Prospective Studies and Meta-analysis of Published Studies.

BACKGROUND: It has been proposed that night shift work could increase breast cancer incidence. A 2007 World Health Organization review concluded, mainly from animal evidence, that shift work involving circadian disruption is probably carcinogenic to humans. We therefore aimed to generate prospective epidemiological evidence on night shift work and breast cancer incidence. METHODS: Overall, 522 246 Million Women Study, 22 559 EPIC-Oxford, and 251 045 UK Biobank participants answered questions on shift work and were followed for incident cancer. Cox regression yielded multivariable-adjusted breast cancer incidence rate ratios (RRs) and 95% confidence intervals (CIs) for night shift work vs no night shift work, and likelihood ratio tests for interaction were used to assess heterogeneity. Our meta-analyses combined these and relative risks from the seven previously published prospective studies (1.4 million women in total), using inverse-variance weighted averages of the study-specific log RRs. RESULTS: In the Million Women Study, EPIC-Oxford, and UK Biobank, respectively, 673, 28, and 67 women who reported night shift work developed breast cancer, and the RRs for any vs no night shift work were 1.00 (95% CI = 0.92 to 1.08), 1.07 (95% CI = 0.71 to 1.62), and 0.78 (95% CI = 0.61 to 1.00). In the Million Women Study, the RR for 20 or more years of night shift work was 1.00 (95% CI = 0.81 to 1.23), with no statistically significant heterogeneity by sleep patterns or breast cancer risk factors. Our meta-analysis of all 10 prospective studies included 4660 breast cancers in women reporting night shift work; compared with other women, the combined relative risks were 0.99 (95% CI = 0.95 to 1.03) for any night shift work, 1.01 (95% CI = 0.93 to 1.10) for 20 or more years of night shift work, and 1.00 (95% CI = 0.87 to 1.14) for 30 or more years. CONCLUSIONS: The totality of the prospective evidence shows that night shift work, including long-term shift work, has little or no effect on breast cancer incidence.

Breast cancer and childhood anthropometry: emerging hypotheses?

In this issue of Breast Cancer Research, Baer and colleagues report a strong protective effect of childhood and adolescent body fatness on premenopausal breast cancer risk based on a large prospective study. Methodological issues are discussed, as are tentative biological interpretations regarding the findings.