Background/Purpose

Lifestyle factors are of major importance for development of RA. Yet, regarding the role of diet surprisingly little is known. The Mediterranean diet, rich in fish, plant food, mono- and polyunsaturated fat, and including moderate wine consumption, has been suggested to protect against e.g. cardiovascular disease, but its effect on RA development has only been studied to a limited extent. The aim of this study was to investigate whether Mediterranean or vegetarian (vs. Western) diet influences the risk of developing RA.

Methods

In the Swedish case-control study Epidemiological Investigation of Rheumatoid Arthritis (EIRA), 1296 incident RA cases and 2661 randomly selected controls matched by age, sex and residential area were enrolled between 2005 and 2012. Type of diet the year before enrolment was ascertained by a single question in a food-frequency-questionnaire, including Western diet, Mediterranean diet, vegetarian diet, vegan diet, or other specified diet. Odds ratios (OR) were estimated for RA overall, and also stratified for anti-citrullinated peptide autoantibodies (ACPA) and rheumatoid factor (RF) status. Adjustments were made for the matching factors in the crude model and additionally for BMI, smoking, formal education and, physical activity in the adjusted model.

Results

9% of the RA-cases (n=122/1269) reported to consume a Mediterranean diet the year before enrolment compared with 12% (309/2661) of the controls, and 4% (n=47/1269) of the RA-cases and 3% (80/2661) of the controls reported to consume a vegetarian diet. After adjustment for the matching factors, a Mediterranean diet was associated with a statistically significant decreased risk of RA compared with Western diet (OR 0.76; 95%CI 0.62-0.97; Table). However, after additional adjustment the association did not remain statistically significant (OR 0.86; 95%CI 0.68-1.08). The results did not change when stratifying by ACPA or RF-status, although there was a tendency towards lower risk with Mediterranean diet in ACPA+ and RF+ patients. Vegetarian diet was not associated with development of RA, neither overall nor in the stratified analysis (Table).  

Conclusion

Self-reported Mediterranean diet was in itself associated with a lower RA risk, but this association disappeared after adjustment for the selected potential confounders. A tendency towards lower risk with Mediterranean diet in ACPA+ and RF+ patients was observed. No association was observed for a vegetarian diet.

Table.Mediterranean or vegetarian diet and risk of RA, stratified by ACPA and RF-status

	Case (n exposed/unexposed)	Controls (n exposed/unexposed)	OR (95%CI) Crudea	OR (95%CI) Adjustedb
Mediterranean Diet
Total	122/1079	309/2151	0.76 (0.62-0.97)	0.86 (0.68-1.08)
ACPA+	79/714	“	0.74 (0.57-0.97)	0.81 (0.61-1.07)
ACPA-	42/356	“	0.84 (0.59-1.19)	0.90 (0.63-1.29)
RF+	74/699	“	0.71 (0.54-0.94)	0.78 (0.58-1.03)
RF-	47/378	“	0.90 (0.65-1.25)	0.98 (0.70-1.39)
Vegetarian Diet
Total	47/1079	80/2151	1.13 (0.77-1.61)	1.17 (0.79-1.71)
ACPA+	35/714	“	1.28 (0.84-1.93)	1.36 (0.89-2.10)
ACPA-	12/356	“	0.82 (0.44-1.54)	0.87 (0.46-1.64)
RF+	34/699	“	1.20 (0.79-1.82)	1.23(0.80-1.92)
RF-	13/378	“	0.92 (0.50-1.69)	1.00 (0.54-1.85)

Unexposed=western diet. ^aAdjustment for the matching factors (age, sex and residential area). ^bAdditional adjustment for BMI, smoking, education and physical activity.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/do-mediterranean-or-vegetarian-diets-influence-risk-of-rheumatoid-arthritis/