Hip fracture is a common serious injury in older women that reduces quality of life and can lead to premature death. In the United Kingdom, hip fractures are estimated to account for 1.5 million hospital bed days used per year due to long hospitalisation and rehabilitation periods post-surgery, costing the National Health Service over £1 billion per year. Diet can affect bone health and risk of hip fracture, with varying risks in women on specific diets, and specific foods and nutrients playing more important roles than others. Vegetarians may be at a greater risk of hip fracture than meat-eaters, and those who don't consume enough protein could be at a greater risk than those with adequate intakes. This research aims to investigate which dietary factors (and in what quantities) might predispose United Kingdom women to a greater risk of hip fracture, and which factors may be protective. The purpose of this study is to better understand the role of diet in reducing hip fracture risk in United Kingdom women. The research will use existing dietary and lifestyle data from the United Kingdom Women's Cohort Study and hospital records of hip fractures.

Background: Hip fracture is an increasingly prevalent global health condition that increases morbidity and mortality. Previous observational studies have shown potential for risk reduction through diet modification, but associations between many dietary factors and hip fracture incidence are uncertain, and evidence in United Kingdom populations is limited. Therefore, this study aims to assess associations between diet and hip fracture incidence in the United Kingdom Women's Cohort.

Research plan and methods: The investigators will utilise dietary and lifestyle data from the United Kingdom Women's Cohort which recruited 35,372 middle-aged women between 1995-1998. This data has been linked with Hospital Episode Statistics to provide hip fracture data of participants.

Cox regression models will be applied to explore potential associations between dietary factors and hip fracture incidence. Dietary factors will be modelled both as categorical and continuous so that models can be fit comparing the risk of hip fracture between categories of intakes and per increment increase in exposure intake (linear dose-response). Cubic splines will be used to model non-linear associations for dietary intake of fruits, vegetables, tea, and coffee since previous research has suggested possible non-linear associations for these variables.

Inclusion Criteria:

• Female
• Ages 35 - 69 years at time of recruitment
• Able to provide informed consent

Exclusion Criteria:

• Male
• Not a resident of England
• Unable to link dietary and lifestyle data with hospital episode data
• Missing covariate data
• Hip fracture or osteoporosis prevalence before or on the date of recruitment

The UK Women's cohort profile is published here: [https://doi.org/10.1093/ije/dyv173\].