Dietary Patterns and Hip Fracture Risk in the UK Biobank
Condition: Hip Fractures
MeSH terms: Fractures, Bone; Hip Fractures
Study type: Observational

Summary: 
      Hip fracture is a common serious injury in older adults that reduces mobility, independence,
      and quality of life, and can lead to premature death. Around 1.6 million cases occur globally
      per year, and continual increases in the number of older adults worldwide suggests that cases
      could reach 4.5 million by 2050. Diet can affect bone health and risk of hip fracture, with
      varying risks in adults on specific diets. There is some evidence that vegetarians may have
      poorer bone health and higher risks of fractures than meat-eaters, but prospective evidence
      for hip fractures is limited, and the influence of factors including diet quality and body
      mass index (BMI) are unclear.

      The main aim of this research is to investigate risk of hip fracture in occasional
      meat-eaters, pescatarians, and vegetarians compared to regular meat-eaters. A secondary aim
      is to determine if risk of hip fracture in these diet groups depends on age, sex, diet
      quality, body mass index, and diet-gene interactions. Thirdly, we will explore the role of
      potential factors underpinning any risk differences, such as BMI, bone mineral density, and
      intake of nutrients that are mostly found in animal-sourced foods. The purpose of this study
      is to better understand hip fracture risk in vegetarian UK adults. The proposed project will
      use existing diet and lifestyle data from the UK Biobank resource, and hospital records of
      hip fractures.
    

Detailed description: 
      Background:

      Hip fracture is an increasingly prevalent health problem in the UK and worldwide that
      increases morbidity and mortality. Previous epidemiological evidence suggests that compared
      to meat-eaters, people following plant-based diets have lower bone mineral density (BMD) and
      a higher risk of fractures. Emerging evidence suggests a higher risk of hip fracture in
      vegetarian women, but prospective evidence of hip fracture risk in these diet groups is
      scarce and limited, particularly in men. Risk differences between diet groups are plausible
      in men and women, for example due to bone or muscle-related nutrient deficiencies or low BMI
      in vegetarians, but underlying mechanisms explaining potential risk differences require
      further investigation.

      This study aims to investigate risk of hip fracture in occasional meat-eaters, pescatarians,
      and vegetarians compared to regular meat-eaters in the UK Biobank cohort. A secondary aim is
      to determine the role of potential modifying factors on associations between each diet group
      and hip fracture risk, including diet quality (determined by adherence to the Alternative
      Healthy Eating Index, AHEI), age, sex, and BMI, as well as investigating interactions between
      diet groups and genotypes on BMD and hip fracture risk. Thirdly, we aim to determine the role
      of potential mediating factors on any observed associations, including BMI, BMD, and intake
      of dietary nutrients abundant in animal products.

      Research plan and methods:

      The investigators will utilise dietary and lifestyle data from the UK Biobank cohort, which
      recruited over 500,000 adults between 2006-2010, and linked hospital records of UK Biobank
      participants to identify hip fracture cases.

      A Cox regression model will be applied to investigate risk of hip fracture in each diet group
      compared to regular meat-eaters, and will be adjusted for relevant confounders. The roles of
      age, sex, AHEI score, BMI, and diet-gene interactions as potential effect modifiers will be
      explored by adding each variable to Cox regression models as interaction terms. Causal
      mediation analysis will be used to determine the role of potential mediators.
    

Intervention name(s): Dietary pattern observed
Intervention type(s): Other
Intervention description(s): Dietary pattern: regular meat-eater, occasional meat-eater, pescatarian, and vegetarian. There are no interventions in this observational cohort.
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Information on the UK Biobank cohort profile is available here:
        https://www.ukbiobank.ac.uk/
      
Biospecimen description: 
      UK Biobank collected biomarker samples with DNA. This project makes use of data from the
      biomarker samples, but no additional samples will be taken and no additional samples will
      taken for this research. No samples will be processed, stored or retained by us. For the
      previously published details of UK Biobank, with anonymised data made available for
      researchers, please see:
      https://www.ukbiobank.ac.uk/enable-your-research/about-our-data/biomarker-data
    
Keywords: Nutrition; Vegetarian; Fracture; Cohort study; Epidemiology; Osteoporosis