Vitamin K, Vitamin D, and Lower Extremity Function: Results from the Osteoarthritis Initiative and Health, Aging and Body Composition Studies

Abstract

Knee osteoarthritis (OA) is the leading cause of impaired lower‐extremity function in older adults. Vitamin K insufficiency has been associated with greater structural knee OA progression, but studies associating vitamin K status with functional consequences of knee OA are lacking. The purpose of this study was to determine the association between vitamin K intake and lower‐extremity function in the Osteoarthritis Initiative (OAI), a prospective observational study of knee OA (n=4497, 58% female, 61±9 years old). Because the mechanisms underlying the role of vitamin K in joint health also implicate vitamin D, we additionally evaluated the association of combined vitamin K and vitamin D intake with lower extremity function. Dietary intakes were estimated using a food frequency questionnaire at baseline. Lower extremity function was assessed at baseline and annually over 4 years using the 20‐meter gait speed and time to complete 5 chair stands. Participants in the highest quartile of vitamin K intake had significantly faster 20‐meter gait speed and chair stand time over 4 years compared those in the lower quartiles (both p‐trend<0.001; analyzed using linear mixed models adjusted for demographics, co‐morbidities, diet and lifestyle characteristics). When vitamin K and D intakes were considered together, those in the highest quartiles of both vitamin K (≥229 mcg/d) and vitamin D (≥600 IU/d) intake had significantly faster gait speed (p<0.001) and chair stand time (p=0.002) over 4 years compared to participants in the highest quartile of either nutrient alone and compared to participants in the lowest quartile of both nutrients. We sought to replicate these findings, given their novelty, in the Healthy, Aging and Body Composition Knee OA sub‐study (n=1102, 60% female, 75±3 years old). Vitamin K and D status were assessed using circulating vitamin K and 25(OH)D at baseline and lower extremity function was assessed using the short physical performance battery (SPPB) and 20‐meter gait speed at baseline and over 4–5 years of follow‐up. Participants with both sufficient vitamin K (≥1.0 nM) and 25(OH)D (≥50nM) had significantly better SPPB scores and faster gait speed over follow‐up compared to those with sufficient levels of either nutrient alone and compared to those who were insufficient in both (p=0.001 and 0.005 respectively; adjusted for demographics, season, co‐morbidities, diet and lifestyle characteristics). These findings suggest vitamin K and vitamin D may be mutually beneficial to lower‐extremity function related to knee OA but need to be confirmed in clinical trials.Support or Funding InformationSupported by the USDA (Cooperative Agreement 58‐1950‐7‐707) and the NIH (grants K01AR063167, P30AG21332, R01AG028050, R01NR012459, contracts N01AG62101, N01AG62103, N01AG62106)