UK universities re-opened in September 2020, amidst the coronavirus epidemic. During the first term, various national social distancing measures were introduced, including banning groups of >6 people and the second lockdown in November; however, outbreaks among university students occurred. We aimed to measure the University of Bristol staff and student contact patterns via an online, longitudinal survey capturing self-reported contacts on the previous day. We investigated the change in contacts associated with COVID-19 guidance periods: post-first lockdown (23/06/2020–03/07/2020), relaxed guidance period (04/07/2020–13/09/2020), ‘rule-of-six’ period (14/09/2020–04/11/2020) and the second lockdown (05/11/2020–25/11/2020). In total, 722 staff (4199 responses) and 738 students (1906 responses) were included in the study. For staff, daily contacts were higher in the relaxed guidance and ‘rule-of-six’ periods than the post-first lockdown and second lockdown. Mean student contacts dropped between the ‘rule-of-six’ and second lockdown periods. For both staff and students, the proportion meeting with groups larger than six dropped between the ‘rule-of-six’ period and the second lockdown period, although was higher for students than for staff. Our results suggest university staff and students responded to national guidance by altering their social contacts. Most contacts during the second lockdown were household contacts. The response in staff and students was similar, suggesting that students can adhere to social distancing guidance while at university. The number of contacts recorded for both staff and students were much lower than those recorded by previous surveys in the UK conducted before the COVID-19 pandemic.

The ‘16Up’ study conducted at the QIMR Berghofer Medical Research Institute from January 2014 to December 2018 aimed to examine the physical and mental health of young Australian twins aged 16−18 years (N = 876; 371 twin pairs and 18 triplet sets). Measurements included online questionnaires covering physical and mental health as well as information and communication technology (ICT) use, actigraphy, sleep diaries and hair samples to determine cortisol concentrations. Study participants generally rated themselves as being in good physical (79%) and mental (73%) health and reported lower rates of psychological distress and exposure to alcohol, tobacco products or other substances than previously reported for this age group in the Australian population. Daily or near-daily online activity was almost universal among study participants, with no differences noted between males and females in terms of frequency or duration of internet access. Patterns of ICT use in this sample indicated that the respondents were more likely to use online information sources for researching physical health issues than for mental health or substance use issues, and that they generally reported partial levels of satisfaction with the mental health information they found online. This suggests that internet-based mental health resources can be readily accessed by adolescent Australians, and their computer literacy augurs well for future access to online health resources. In combination with other data collected as part of the ongoing Brisbane Longitudinal Twin Study, the 16Up project provides a valuable resource for the longitudinal investigation of genetic and environmental contributions to phenotypic variation in a variety of human traits.

Low-Se status may be associated with a higher risk of notably advanced prostate cancer. In a Danish population with a relatively low Se intake, we investigated the association between pre-diagnostic Se status and (1) the risk of total, advanced and high-grade prostate cancer and (2) all-cause and prostate cancer-specific mortality among men with prostate cancer. Within the Danish ‘Diet, Cancer and Health’ cohort, including 27 179 men, we identified 784 cases with incident prostate cancer through 2007. Each case was risk set-matched to one control. Two-thirds (n 525) of the cases had advanced disease at the time of diagnosis, and among these 170 had high-grade disease; 305 cases died (n 212 from prostate cancer) during follow-up through 2012. Plasma Se was not associated with total or advanced prostate cancer risk, but higher Se levels were associated with a lower risk of high-grade disease (HR 0·77; 95 % CI 0·64, 0·94; P=0·009). In survival analyses, a higher level of plasma Se was associated with a lower risk of all-cause (HR 0·92; 95 % CI 0·85, 1·00; P=0·04), but not prostate cancer-specific mortality. Higher levels of selenoprotein P were associated with a lower risk of high-grade disease (HR 0·85; 95 % CI 0·74, 0·97; P=0·01), but not with the risk of or mortality from advanced prostate cancer. In conclusion, levels of plasma Se and selenoprotein P were not associated with the risk of total and advanced prostate cancer, but higher levels of these two biomarkers were associated with a lower risk of high-grade disease.

A trend toward greater body size in dizygotic (DZ) than in monozygotic (MZ) twins has been suggested by some but not all studies, and this difference may also vary by age. We analyzed zygosity differences in mean values and variances of height and body mass index (BMI) among male and female twins from infancy to old age. Data were derived from an international database of 54 twin cohorts participating in the COllaborative project of Development of Anthropometrical measures in Twins (CODATwins), and included 842,951 height and BMI measurements from twins aged 1 to 102 years. The results showed that DZ twins were consistently taller than MZ twins, with differences of up to 2.0 cm in childhood and adolescence and up to 0.9 cm in adulthood. Similarly, a greater mean BMI of up to 0.3 kg/m2 in childhood and adolescence and up to 0.2 kg/m2 in adulthood was observed in DZ twins, although the pattern was less consistent. DZ twins presented up to 1.7% greater height and 1.9% greater BMI than MZ twins; these percentage differences were largest in middle and late childhood and decreased with age in both sexes. The variance of height was similar in MZ and DZ twins at most ages. In contrast, the variance of BMI was significantly higher in DZ than in MZ twins, particularly in childhood. In conclusion, DZ twins were generally taller and had greater BMI than MZ twins, but the differences decreased with age in both sexes.

No study has yet investigated the intake of different types of whole grain (WG) in relation to all-cause and cause-specific mortality in a healthy population. The aim of the present study was to investigate the intake of WG products and WG types in relation to all-cause and cause-specific mortality in a large Scandinavian HELGA cohort that, in 1992–8, included 120 010 cohort members aged 30–64 years from the Norwegian Women and Cancer Study, the Northern Sweden Health and Disease Study, and the Danish Diet Cancer and Health Study. Participants filled in a FFQ from which data on the intake of WG products were extracted. The estimation of daily intake of WG cereal types was based on country-specific products and recipes. Mortality rate ratios (MRR) and 95 % CI were estimated using the Cox proportional hazards model. A total of 3658 women and 4181 men died during the follow-up (end of follow-up was 15 April 2008 in the Danish sub-cohort, 15 December 2009 in the Norwegian sub-cohort and 15 February 2009 in the Swedish sub-cohort). In the analyses of continuous WG variables, we found lower all-cause mortality with higher intake of total WG products (women: MRR 0·89 (95 % CI 0·86, 0·91); men: MRR 0·89 (95 % CI 0·86, 0·91) for a doubling of intake). In particular, intake of breakfast cereals and non-white bread was associated with lower mortality. We also found lower all-cause mortality with total intake of different WG types (women: MRR 0·88 (95 % CI 0·86, 0·92); men: MRR 0·88 (95 % CI 0·86, 0·91) for a doubling of intake). In particular, WG oat, rye and wheat were associated with lower mortality. The associations were found in both women and men and for different causes of deaths. In the analyses of quartiles of WG intake in relation to all-cause mortality, we found lower mortality in the highest quartile compared with the lowest for breakfast cereals, non-white bread, total WG products, oat, rye (only men), wheat and total WG types. The MRR for highest v. lowest quartile of intake of total WG products was 0·68 (95 % CI 0·62, 0·75, Ptrend over quartiles< 0·0001) for women and 0·75 (95 % CI 0·68, 0·81, Ptrend over quartiles< 0·0001) for men. The MRR for highest v. lowest quartile of intake of total WG types was 0·74 (95 % CI 0·67, 0·81, Ptrend over quartiles< 0·0001) for women and 0·75 (95 % CI 0·68, 0·82, Ptrend over quartiles< 0·0001) for men. Despite lower statistical power, the analyses of cause-specific mortality according to quartiles of WG intake supported these results. In conclusion, higher intake of WG products and WG types was associated with lower mortality among participants in the HELGA cohort. The study indicates that intake of WG is an important aspect of diet in preventing early death in Scandinavia.

For over 100 years, the genetics of human anthropometric traits has attracted scientific interest. In particular, height and body mass index (BMI, calculated as kg/m2) have been under intensive genetic research. However, it is still largely unknown whether and how heritability estimates vary between human populations. Opportunities to address this question have increased recently because of the establishment of many new twin cohorts and the increasing accumulation of data in established twin cohorts. We started a new research project to analyze systematically (1) the variation of heritability estimates of height, BMI and their trajectories over the life course between birth cohorts, ethnicities and countries, and (2) to study the effects of birth-related factors, education and smoking on these anthropometric traits and whether these effects vary between twin cohorts. We identified 67 twin projects, including both monozygotic (MZ) and dizygotic (DZ) twins, using various sources. We asked for individual level data on height and weight including repeated measurements, birth related traits, background variables, education and smoking. By the end of 2014, 48 projects participated. Together, we have 893,458 height and weight measures (52% females) from 434,723 twin individuals, including 201,192 complete twin pairs (40% monozygotic, 40% same-sex dizygotic and 20% opposite-sex dizygotic) representing 22 countries. This project demonstrates that large-scale international twin studies are feasible and can promote the use of existing data for novel research purposes.

The prevalence of dietary supplement use varies largely among populations, and previous studies have indicated that it is high in the Danish population compared with other European countries. The diversity in supplement use across countries indicates that cultural and environmental factors could influence the use of dietary supplements. Only few studies investigating the use of dietary supplements have been conducted in the Danish population. The present cross-sectional study is based on 54 948 Danes, aged 50–64 years, who completed self-administrated questionnaires on diet, dietary supplements and lifestyle between 1993 and 1997. A health index including smoking, physical activity, alcohol and diet, and a metabolic risk index including waist circumference, urinary glucose and measured hypertension were constructed. Logistic regression was used to investigate these determinants in relation to the intake of dietary supplements. We found that 71 % of the participants were dietary supplement users; female sex, older age groups and higher educated participants were more likely to be users of any dietary supplements. One additional point in the health index was associated with 19, 16 and 9 % higher likelihood of being user of any, more common and less common supplements, respectively. In the metabolic risk index, one additional point was associated with 17 and 16 % lower likelihood of being user of any supplement and more common supplements, respectively. No significant association was found for less common supplement use. In conclusion, those with the healthiest lifestyle were more likely to use dietary supplements. Thus, lifestyle and dietary composition should be considered as confounders on supplement use and health outcomes.

Whole-grain intake has been reported to be associated with a lower risk of several lifestyle-related diseases such as type 2 diabetes, CVD and some types of cancers. As measurement errors in self-reported whole-grain intake assessments can be substantial, dietary biomarkers are relevant to be used as complementary tools for dietary intake assessment. Alkylresorcinols (AR) are phenolic lipids found almost exclusively in whole-grain wheat and rye products among the commonly consumed foods and are considered as valid biomarkers of the intake of these products. In the present study, we analysed the plasma concentrations of five AR homologues in 2845 participants from ten European countries from a nested case–control study in the European Prospective Investigation into Cancer and Nutrition. High concentrations of plasma total AR were found in participants from Scandinavia and Central Europe and lower concentrations in those from the Mediterranean countries. The geometric mean plasma total AR concentrations were between 35 and 41 nmol/l in samples drawn from fasting participants in the Central European and Scandinavian countries and below 23 nmol/l in those of participants from the Mediterranean countries. The whole-grain source (wheat or rye) could be determined using the ratio of two of the homologues. The main source was wheat in Greece, Italy, the Netherlands and the UK, whereas rye was also consumed in considerable amounts in Germany, Denmark and Sweden. The present study demonstrates a considerable variation in the plasma concentrations of total AR and concentrations of AR homologues across ten European countries, reflecting both quantitative and qualitative differences in the intake of whole-grain wheat and rye.

The phyto-oestrogen enterolactone has been hypothesised to protect against hormone-dependent cancers, probably through its anti-oestrogenic potential. We investigated whether a higher level of plasma enterolactone was associated with a lower incidence of endometrial cancer in a case–cohort study in the ‘Diet, Cancer and Health’ cohort. The cohort study included 29 875 women aged 50–64 years enrolled between 1993 and 1997. Information on diet and lifestyle was provided by self-administrated questionnaires and blood was drawn from each participant. Time-resolved fluoroimmunoassay was used for biochemical determination of plasma enterolactone. A total of 173 cases and 149 randomly selected cohort members were included. We estimated incidence rate ratio (IRR) and 95 % CI by a Cox proportional hazards model. A 20 nmol/l higher plasma concentration of enterolactone was associated with a non-significant lower risk of endometrial cancer (IRR 0·93, 95 % CI 0·84, 1·04). When excluding women with low enterolactone concentrations (quartile 1) due to potential recent antibiotic use, the association became slightly stronger, but remained non-significant (IRR 0·90, 95 % CI 0·79, 1·02). Menopausal status, hormone replacement therapy or BMI did not modify the association. In conclusion, we found some support for a possible inverse association between plasma enterolactone concentration and endometrial cancer incidence.

Colorectal cancer (CRC) is a multi-factorial disease in which diet is believed to play a role. Little is known about the health effects of specific regional diets. The Nordic diet is high in fat and sugar but also includes a range of traditional products with anticipated health-promoting effects. The aim of this cohort study was to determine whether a healthy Nordic food index consisting of fish, cabbage, rye bread, oatmeal, apples, pears and root vegetables was related to CRC incidence. Data were obtained from a prospective cohort study of 57 053 Danish men and women aged 50–64 years, of whom 1025 developed CRC (13 years' follow-up). Incidence rate ratios (IRR) with 95 % CI were calculated from Cox proportional hazard models. Women who strongly adhered to a healthy Nordic food index had a 35 % lower incidence of CRC than women with poor adherence (adjusted IRR, 0·65; 95 % CI 0·46, 0·94); a similar tendency was found for men. Women had a 9 % lower incidence of CRC per point adherence to the healthy Nordic food index, but no significant effect was found for men. A regional diet based on healthy Nordic food items was therefore associated with a lower incidence of CRC in women. The protective effect was of the same magnitude as previously found for the Mediterranean diet, suggesting that healthy regional diets should be promoted in order to ensure health; this will also preserve cultural heredity and the environment.

Monozygotic (MZ) twins may be discordant for complex traits due to differential environmental exposure in utero, epigenetic variability in imprinting, X chromosome inactivation, or stochastic effects. Occasionally MZ twins may be discordant for chromosomal and single gene disorders due to somatic mosaicism. For complex traits, which are due to the interactive effects of multiple genes and environmental factors, the affected twin of a discordant MZ pair offers the possibility for identifying somatic mutations in candidate genes. DNA sequencing of candidate genes in discordant MZ twins can identify those rare etiologic mutational events responsible for the different phenotypes since the confounding effects of common single nucleotide polymorphisms are eliminated, as DNA sequences should be identical in MZ pairs. In this report we describe the extensive DNA sequencing of 18 candidate genes in a sample of MZ and dizygotic (DZ) twins with nonsyndromic cleft lip with or without cleft palate. We were unable to identify any somatic differences in approximately 34 Kb of DNA sequenced in 13 MZ pairs, for a total of approximately 900 Kb of sequence comparisons, supporting the hypothesis that nonetiologic posttwinning mutations are rare. While no etiologic variants were identified in this study, sequence comparisons of discordant MZ twins can serve as a tool for identifying etiologic mutations in clefting and other complex traits.

Phenotypically discordant monozygotic twins offer the possibility of gene discovery through delineation of molecular abnormalities in one member of the twin pair. One proposed mechanism of discordance is postzygotically occurring genomic alterations resulting from mitotic recombination and other somatic changes. Detection of altered genomic fragments can reveal candidate gene loci that can be verified through additional analyses. We investigated this hypothesis using array comparative genomic hybridization; the 50K and 250K Affymetrix GeneChip® SNP arrays and an Illumina custom array consisting of 1,536 SNPs, to scan for genomic alterations in a sample of monozygotic twin pairs with discordant cleft lip and/or palate phenotypes. Paired analysis for deletions, amplifications and loss of heterozygosity, along with sequence verification of SNPs with discordant genotype calls did not reveal any genomic discordance between twin pairs in lymphocyte DNA samples. Our results demonstrate that postzygotic genomic alterations are not a common cause of monozygotic twin discordance for isolated cleft lip and/or palate. However, rare or balanced genomic alterations, tissue-specific events and small aberrations beyond the detection level of our experimental approach cannot be ruled out. The stability of genomes we observed in our study samples also suggests that detection of discordant events in other monozygotic twin pairs would be remarkable and of potential disease significance.

Acrylamide (AA) is a probable human carcinogen that is formed in heat-treated carbohydrate-rich foods. The validity of FFQ to assess AA exposure has been questioned. The aim of the present cross-sectional study was to investigate dietary determinants of Hb-AA and Hb-glycidamide (GA) adducts. The study included 537 non-smoking women aged 50–65 years who participated in the Diet, Cancer and Health cohort (1993–97). At study baseline, blood samples and information on dietary and lifestyle variables obtained from self-administered questionnaires were collected. From blood samples, Hb-AA and Hb-GA in erythrocytes were analysed by liquid chromatography/MS/MS. Dietary determinants were evaluated by multiple linear regression analyses adjusted for age and smoking behaviour among ex-smokers. The median for Hb-AA was 35 pmol/g globin (5th percentile 17, 95th percentile 89) and for Hb-GA 21 pmol/g globin (5th percentile 8, 95th percentile 49). Of the dietary factors studied, intakes of coffee and chips were statistically significantly associated with a 4 % per 200 g/d (95 % CI 2, 7; P < 0·0001) and an 18 % per 5 g/d (95 % CI 6, 31; P = 0·002) higher Hb-AA, respectively. This model explained 17 % of the variation in Hb-AA. Intakes of coffee and biscuits/crackers were statistically significantly associated with a 3 % per 200 g/d (95 % CI 1, 6; P = 0·005) and 12 % per 10 g/d (95 % CI 3, 23; P = 0·01) higher Hb-GA, respectively. This model explained 12 % of the variation in Hb-GA. In conclusion, only a few dietary determinants of Hb-AA and Hb-GA were identified. Thus, the present study implies that dietary intake measured by an FFQ explains only to a limited extent the variation in Hb-AA and Hb-GA concentrations.

Prospective epidemiological studies have reported that a higher fruit and vegetable intake is associated with a lower risk of CHD. The aim of the present study was to examine associations between fruit and vegetable consumption, in particular the subgroupings citrus fruits, apples and cruciferous vegetables, and the risk of acute coronary syndrome (ACS). During a median follow-up of 7·7 years, 1075 incident ACS cases were identified among 53 383 men and women, aged 50–64 years at recruitment into the Diet, Cancer and Health cohort study in 1993–7. Fruit and vegetable intake was estimated from a validated FFQ, and ACS incidence rate ratios (IRR) were estimated using Cox proportional hazards models. Overall, a tendency towards a lower risk of ACS was observed for both men and women with higher fruit and vegetable consumption. For men, we found an inverse association for apple intake (IRR per 25 g/d: 0·97; 95 % CI 0·94, 0·99). This association was also seen among women, albeit borderline significant. However, a higher risk was seen among women with higher fruit juice intake (IRR per 25 g/d: 1·04; 95 % CI 1·00, 1·08). The present results provide some support for previously observed inverse associations between fresh fruit intake, particularly apples, and ACS risk.