Rheumatoid arthritis (RA) is the most common inflammatory arthritis, affecting around 1% of the UK population. It affects around 400,000 adults and is characterised by synovial inflammation, cartilage and bone damage that requires lifelong treatment and represents a significant burden for both the individual and society. Diet can affect inflammatory status and RA risk, with varying risks for women on specific diets. Low to moderate levels of alcohol consumption may be associated with lower risk of RA, and those who do not consume enough fruit and vegetables could be at a greater risk than those with adequate intakes. Our research aim is to better understand the role of diet in reducing RA 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 RA incidence.

Background: Rheumatoid arthritis (RA) is a typical inflammatory arthritic disease that increases morbidity and mortality of cardiovascular diseases worldwide. Previous observational studies have shown potential for risk reduction through dietary factors modification, but associations between most of dietary factors and RA incidence are still uncertain, and evidence in United Kingdom populations is limited. Therefore, this study aims to assess associations between diet and RA incidence in the United Kingdom Women's Cohort.

Research plan and methods: The dietary and lifestyle data from the United Kingdom Women's Cohort, which recruited 35,372 middle-aged women between 1995-1998, will be used. These data were linked to Hospital Episode Statistics to provide data on the incidence of RA in participants.

Cox regression models will be applied to explore potential associations between dietary factors and RA incidence. Dietary factors will be modelled both as categorical and continuous variables so that models can be fit comparing the risk of RA between categories of intakes and per increment increase in exposure intake (linear dose-response). Restricted cubic splines will be used to model non-linear associations for dietary intake of alcohol, 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
• Rheumatoid arthritis records before or on the date of recruitment

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

The full data access policy for the UK Women's Cohort Study is available via the study website (https://ukwcs.leeds.ac.uk/).

The full data access policy for the UK Women's Cohort Study is available via the study website (https://ukwcs.leeds.ac.uk/).

The full data access policy for the UK Women's Cohort Study is available via the study website (https://ukwcs.leeds.ac.uk/).