The UK Women's Cohort Study: comparison of vegetarians, fish-eaters and meat-eaters

Background: This paper describes the development of the UK Women's Cohort Study and presents cohort baseline characteristics. Methods: In total, 35 372 women, aged 35–69 years at recruitment, were selected to ensure a wide range of dietary intakes. Diet was assessed by a 217-item food-frequency questionnaire (FFQ). Detailed lifestyle information was collected by postal questionnaire. Vegetarians, fish-eaters and meat-eaters were compared. Results: The cohort women are mainly white, well-educated, middle-class and married with children. They are health-conscious with only 11% current smokers and 58% taking dietary supplements. Twenty-eight per cent of subjects self-report as being vegetarian and 1% as vegan. However, only 18% are defined as 'vegetarian' from the FFQ. Fat provides 32% of energy; vitamin and mineral intakes are high, with a broad range of intakes. Meat-eaters are older, with a higher body mass index (BMI) and the lowest intakes of carbohydrate, fibre, vitamin C, folate, iron and calcium. Other fish-eaters are similar to vegetarians. Vegetarians have the lowest intakes of protein, fat and saturated fat. Oily fish-eaters have the lowest BMI; are the least likely to smoke or use full-fat milk; and are the most likely to use dietary supplements and consume the most fruit and vegetables. Oily fish-eaters have the highest total energy intake and vegetarians the lowest. Semi-skimmed milk, bread, potatoes, wine, bananas and muesli are important contributors to energy for all groups

Birthweight and childhood wheezing disorders: a systematic review and meta-analysis

BACKGROUND: Previous observational studies have claimed that birthweight and childhood wheezing disorders are associated although the results remained inconsistent. One systematic review and two systematic reviews that included meta-analyses reported inconsistent results. We aimed to conduct a systematic review and meta-analysis to investigate this. METHODS: An online search of published papers linking childhood asthma and wheezing disorders with birthweight up to February 2014 was carried out using EMBASE and Medline medical research databases. Summary odds ratios (OR) were estimated using random-effects models. Sub-group meta-analyses were performed to assess the robustness of risk associations and between-study heterogeneity. RESULTS: A total of 37 studies comprising 1,712,737 participants were included in our meta-analysis. The unadjusted summary ORs for risk of childhood wheezing disorders associated with low birthweight (4.0kg) as compared to the 2.5-4.0kg birthweight group was 1.02 (95% CI: 0.99 to 1.04, P=0.13). There was substantial heterogeneity in the unadjusted low birthweight risk estimates which was not accounted for by predefined study characteristics. There was no significant heterogeneity in the high birthweight risk estimates. There was some evidence of funnel plot asymmetry and small study effects in the low birthweight (2.5kg versus ≥2.5kg and <2.5kg versus 2.5-4.0kg) odds ratio estimates. CONCLUSION: Our results suggest that low birth (<2.5kg) is an independent risk factor for wheezing disorders during childhood and adolescence although there was substantial heterogeneity among the risk estimates. However, we found no significant association of high birthweight with wheezing disorders

Letter: questions regarding the diagnostic performance of serum assays for atrophic gastritis – authors’ reply

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Assessment of the Fitbit Charge 2 for monitoring heart rate

Fitness trackers are devices or applications for monitoring and tracking fitness-related metrics such as distance walked or run, calorie consumption, quality of sleep and heart rate. Since accurate heart rate monitoring is essential in fitness training, the objective of this study was to assess the accuracy and precision of the Fitbit Charge 2 for measuring heart rate with respect to a gold standard electrocardiograph. Fifteen healthy participants were asked to ride a stationary bike for 10 minutes and their heart rate was simultaneously recorded from each device. Results showed that the Fitbit Charge 2 underestimates the heart rate. Although the mean bias in measuring heart rate was a modest -5.9 bpm (95% CI: -6.1 to -5.6 bpm), the limits of agreement, which indicate the precision of individual measurements, between the Fitbit Charge 2 and criterion measure were wide (+16.8 to -28.5 bpm) indicating that an individual heart rate measure could plausibly be underestimated by almost 30 bpm

Risk of Hip Fracture in Meat Eaters, Pescatarians, and Vegetarians: A Prospective Cohort Study of 413,914 UK Biobank Participants

Background: Meat-free diets may be associated with a higher risk of hip fracture, but prospective evidence is limited. We aimed to investigate the risk of hip fracture in occasional meat-eaters, pescatarians, and vegetarians compared to regular meat-eaters in the UK Biobank, and to explore the role of potential mediators of any observed risk differences. Methods: Middle-aged UK adults were classified as regular meat-eaters (n=258,765), occasional meat-eaters (n=137,954), pescatarians (n=9557), or vegetarians (n=7638) based on dietary and lifestyle information at recruitment (2006-2010). Incident hip fractures were identified by record linkage to Hospital Episode Statistics up to September 2021. Multivariable Cox regression models were used to estimate associations between each diet group and hip fracture risk, with regular meat-eaters as the reference group, over a median follow-up time of 12.5 years. Findings: Among 413,914 women, 3503 hip fractures were observed. After adjustment for confounders, vegetarians (HR (95% CI): 1·50 (1·18, 1·91)) but not occasional meat-eaters (0·99 (0·93, 1·07)) or pescatarians (1·08 (0·86, 1·35)) had a greater risk of hip fracture than regular meat-eaters. This is equivalent to an adjusted absolute risk difference of 3·2 (1·2, 5·8) more hip fractures per 1000 people over 10 years in vegetarians. There was limited evidence of effect modification by BMI on hip fracture risk across diet groups (pinteraction = 0·08), and no clear evidence of effect modification by age or sex (pinteraction = 0·9 and 0·3, respectively). Mediation analyses suggest that BMI explained 28% of the observed risk difference between vegetarians and regular meat-eaters (95% CI: 1·1%, 69·8%). Interpretation: Vegetarian men and women had a higher risk of hip fracture than regular meat-eaters, and this was partly explained by their lower BMI. Ensuring adequate nutrient intakes and weight management are therefore particularly important in vegetarians in the context of hip fracture prevention

Infant arterial stiffness and maternal iron status in pregnancy: A UK birth cohort (Baby VIP study)

Background In animal studies, iron deficiency during pregnancy has been linked to increased offspring cardiovascular risk. No previous population studies have measured arterial stiffness early in life to examine its association with maternal iron status. Objective This study aimed to examine the association between maternal iron status in early pregnancy with infant brachio-femoral pulse wave velocity (PWV). Methods The Baby VIP (Baby’s Vascular health and Iron in Pregnancy) study is a UK-based birth cohort which recruited 362 women after delivery from the Leeds Teaching Hospitals postnatal wards. Ferritin and transferrin receptor levels were measured in maternal serum samples previously obtained in the first trimester. Infant brachio-femoral PWV was measured during a home visit at 2-6 weeks. Results Iron depletion (ferritin <15 ug/L) was detected in 79 (23%) women in early pregnancy. Infant PWV (m=6.7 m/s, sd=1.3, n=284) was not associated with maternal ferritin (adjusted change per 10 ug/L= 0.02, 95% CI -0.01, 0.1), nor with iron depletion (adjusted change = -0.2, 95% CI -0.6, 0.2). No evidence of association was observed between maternal serum transferrin receptor level or its ratio to ferritin with infant PWV. Maternal anaemia (<11 g/dL) at ≤20 weeks gestation was associated with a 1.0 m/s increase in infant PWV (adjusted 95% CI 0.1, 1.9). Conclusion This is the largest study to-date which assessed peripheral PWV as a measure of arterial stiffness in infants. There was no evidence of an association between markers of maternal iron status early in pregnancy and infant PWV

Caffeine intake during pregnancy and adverse birth outcomes: a systematic review and dose–response meta-analysis

Caffeine is commonly consumed during pregnancy, crosses the placenta, with fetal serum concentrations similar to the mother’s, but studies of birth outcome show conflicting findings. We systematically searched Medline and Embase for relevant publications. We conducted meta-analysis of dose–response curves for associations between caffeine intake and spontaneous abortion, stillbirth, preterm delivery, low birth weight and small for gestational age (SGA) infants. Meta-analyses included 60 unique publications from 53 cohort and case–control studies. An increment of 100 g caffeine was associated with a 14 % (95 % CI 10–19 %) increase in risk of spontaneous abortion, 19 % (5–35 %) stillbirth, 2 % (-2 to 6 %) preterm delivery, 7 % (1–12 %) low birth weight, and 10 % (95 % CI 6–14 %) SGA. There was substantial heterogeneity in all models, partly explained by adjustment for smoking and previous obstetric history, but not by prospective assessment of caffeine intake. There was evidence of small-study effects such as publication bias. Greater caffeine intake is associated with an increase in spontaneous abortion, stillbirth, low birth weight, and SGA, but not preterm delivery. There is no identifiable threshold below which the associations are not apparent, but the size of the associations are generally modest within the range of usual intake and are potentially explained by bias in study design or publication. There is therefore insufficient evidence to support further reductions in the maximum recommended intake of caffeine, but maintenance of current recommendations is a wise precaution

Associations of clothing size, adiposity and weight change with risk of postmenopausal breast cancer in the UK Women’s Cohort Study (UKWCS)

Objectives: Breast cancer is associated with overweight and obesity after menopause. However, clothing size as a proxy of adiposity in predicting postmenopausal breast cancer is not widely studied. We aimed to explore the relationships between postmenopausal breast cancer risk with adipose indicators (including clothing sizes) and weight change over adulthood. Design: Prospective cohort study. Setting: England, Wales and Scotland. Participants: 17 781 postmenopausal women from the UK Women’s Cohort Study. Primary: outcome measure Incident cases of malignant breast cancers (International Classification of Diseases (ICD) 9 code 174 and ICD 10 code C50). Results: From 282 277 person-years follow-up, there were 946 incident breast cancer cases with an incidence rate of 3.35 per 1000 women. Body mass index (HR: 1.04; 95% CI: 1.02 to 1.07), blouse size (HR: 1.10; 1.03 to 1.18), waist circumference (HR: 1.07; 1.01 to 1.14) and skirt size (HR: 1.14;1.06 to 1.22) had positive associations with postmenopausal breast cancer after adjustment for potential confounders. Increased weight over adulthood (HR: 1.02; 1.01 to 1.03) was also associated with increased risk for postmenopausal breast cancer. Conclusions: Blouse and skirt sizes can be used as adipose indicators in predicting postmenopausal breast cancer. Maintaining healthy body weight over adulthood is an effective measure in the prevention of postmenopausal breast cancer

Associations between nut consumption and health vary between omnivores, vegetarians, and vegans

Regular nut consumption is associated with reduced risk factors for chronic disease; however, most population-based studies lack consideration of effect modification by dietary pattern. The UK Women’s Cohort Study (UKWCS) provides an ideal opportunity to examine relationships between nut consumption and chronic disease risk factors in a large sample with diverse dietary patterns. Nut and nutrient intake from 34,831 women was estimated using a food frequency questionnaire among self-identified omnivores, vegetarians and vegans. In this cross-sectional analysis, higher nut consumption was associated with lower body weight (difference between highest and lowest consumption categories from adjusted model: 6.1kg; 95%CI: 4.7, 7.6) body mass index (BMI, 2.4 units difference; 95%CI: 1.9, 2.9), and waist circumference (2.6cm difference; 95%CI: 1.4, 3.8) (all P for linear trend < 0.001). Higher nut consumption was also associated with reduced prevalence of high cholesterol and high blood pressure; having a history of heart attack, diabetes and gallstones; and markers of diet quality (all adjusted P for linear trend ≤0.011). Higher nut consumption appeared overall to be associated with greater benefits amongst omnivores compared to vegetarians and vegans. Findings support existing literature around beneficial effects of nut consumption and suggest that benefits may be larger among omnivores. Nut promotion strategies may have the highest population impact by specifically targeting this group