The effect of vitamin D and physical activity on knee osteoarthritis symptoms in older obese adults : a mixed methods study

Abstract

Background: There is an inverse relationship between Vitamin D concentrations and KOA but the effects of Vitamin D supplementation on KOA symptoms are poorly understood. Physical activity (PA) is recommended for KOA yet evidence on how to sustain increased PA is limited. Online PA interventions offer advantages including personalisation and scalability. This pilot study explored the acceptability and feasibility of vitamin D and PA interventions within an older obese KOA population. Methods: Patients meeting our inclusion criteria (age 50-70y, BMI 30-40kg/m2, diagnosed symptomatic KOA ACR criteria) were recruited (March-April/September–December 2015) from eight GP surgeries. Eligible individuals attended a study visit where blood samples, questionnaires, knee assessments and PA accelerometry (3-5 day accelerometry) were taken. Screening was performed for the 3-month pilot intervention study (25(OH)D 25-50nmol/L OR <60min/week moderate activity) and eligible participants were given either daily Vitamin D supplements (2000IU [50μg]) or access to an online PA programme. Assessments were repeated 6 and 12 weeks later and a qualitative interview to explore participants views on acceptability of the study performed immediately after the 12 week visit. Results: Eight GP surgeries identified 791 participants of whom 45 (5.7%) were eligible and attended the study visit. Pilot intervention study screening yielded 17 (2.1%) participants; nine were allocated to each intervention group. The average compliance to the vitamin D intervention was 99% compliance (defined as % tablets taken) and 67% compliance with the PA interventions (defined as use of website beyond registration visit). The PA intervention resulted in a mean decrease of 107 minutes (95% CI: -259.8, 45.0) daily sedentary time and mean increase of 4.4 minutes (95% CI -3.0, 11.8) daily moderate activity time. The Vitamin D intervention led to a mean increase in plasma 25(OH)D concentration of 51nmol/L (SD: ±23.1). Feedback from interviews suggested recruitment and interventions were acceptable and suggestion for improvements on study materials were made. ii Conclusion: Recruitment from GP surgeries and delivery of a Vitamin D and online-based PA intervention is feasible. Most participants were compliant to study procedures and data suggest improved PA and vitamin D status after the respective interventions. Further studies are needed to further pilot test improvements and test the effectiveness of the interventions.