Inflammatory potential of diet and risk of knee osteoarthritis: data from the osteoarthritis initiative

Abstract

Purpose: Diet plays a fundamental role in prevention of many chronic diseases by regulating inflammation and body weight. The evidence of diet in OA development is accumulating. We aimed to examine the relation of inflammatory potential of diet, a modifiable risk factor, to incident knee osteoarthritis (OA) and the role of BMI in the association of interest. Methods: We used data from the Osteoarthritis Initiative. Dietary inflammatory index®(DII®) was calculated based on theBlock Brief 2000 Food Frequency Questionnaire and categorized into sex-specific quartiles. DII® is a literature-derived population-based scoring algorithm to assess the inflammatory potential of diet as a whole and was evaluated for validity and shown to predict inflammatory markers. A higher score of DII® indicates a greater inflammatory potential of diet (i.e., pro-inflammatory effect of diet). Outcomes were incident radiographic knee OA (ROA) (i.e., a KL grade ≥2) and incident symptomatic knee OA (SxOA) (i.e., a combination of a frequent knee pain and ROA). We examined the association of DII® with the risk of knee ROA (or SxOA) by comparing a higher quartile (Q2, Q3 and Q4) with the lowest quartile (Q1: reference category) using generalized estimating equations to account for the correlation between two knees for each participant. In the base model (model 1), we adjusted for age, sex (men vs. women), race (white vs. non-white) and total energy intake (kcal/day). In model 2, we further adjusted for educational attainment (below college vs college or above), annual income (<50,000 US$ vs ≥50,000 US$), tobacco use (non-smoker vs former and current smoker) and PASE score. We tested linear trends using the median value of each quartile of DII®as a continuous variable in the regression model. We conducted sensitivity analyses by including knee replacement due to knee OAduring the follow-up period as incident knee ROA or SxOA, respectively. We performed mediation analyses to assess mediation effect of BMI in DII®-OA relation. Results: We included 1786 and 2940 eligible participants in the final analyses for the association of DII®with incident knee ROA and SxOA, respectively (Figure 1). We identified 232 and 978 knees developed ROA and SxOA among eligible participants over 48-month follow-up period, respectively. Compared with the lowest quartile of DII®, odds ratio (OR) of incident ROA for the highest quartile of DII®was 1.73 (95% confidence interval (CI): 1.15 to 2.62, P for trend= 0.007) (Table 1). The corresponding OR of SxOA was 1.43 (95% CI: 1.16 to 1.76, P for trend = 0.001) (Table 1). When total knee replacement due to knee OA was counted as an incident case of either ROA or SxOA, the results did not change materially.The DII®-OA association was significantly mediated via BMI with an indirect effect of 1.05 (95% CI: 1.02,1.08) for ROA and 1.05 (95% CI: 1.05, 1.11) for SxOA, accounting for 15.6% and 36.0% of total effect, respectively (Table 2). Conclusions: A higher inflammatory potential of diet increased the risk of knee OA. The association was significantly mediated via BMI. A role of inflammatory potential in dietary strategy for OA was indicated.View Large Image Figure ViewerDownload Hi-res image Download (PPT)View Large Image Figure ViewerDownload Hi-res image Download (PPT)