The (cost-)effectiveness of a combined lifestyle intervention in overweight and obese patients with knee osteoarthritis in primary care

BACKGROUND: Knee osteoarthritis (OA) is a chronic condition characterized by pain and impaired function and strongly contributes to physical disability. With an aging population, the prevalence of OA is estimated to be the number one chronic disease in the Netherlands in 2040. A high BMI is a major modifiable risk factor for knee OA. In those with established knee OA in secondary care, there is evidence that weight loss has notable effects on pain and function. Since 2019 it is possible for GPs in The Netherlands to refer knee OA patients with overweight/obesity to a combined lifestyle intervention. However, GPs indicate that this is only very limitedly done because of the unfamiliarity with the intervention, unawareness of the target group and questions on effectiveness; the (cost-)effectiveness of this intervention in the OA target population and its setting in the Netherlands has not yet been investigated. The fact that about 68% of knee OA patients in general practice are overweight/obese, highlights the importance of an (cost)effective lifestyle intervention in primary care for this population. This is especially important as patients with knee OA significantly differ from the other target populations for the combined lifestyle intervention: they experience pain during physical activities and limited in functional performance, which are key targets of the intervention. GENERAL AIM: To investigate the (cost-)effectiveness of a combined lifestyle intervention, in addition to usual care, in early knee OA patients with overweight/obesity in primary care in comparison with usual care alone. Moreover, factors that may mediate the effects of diet and exercise on clinical and structural outcomes will be explored and facilitators for implementation will be studied among patients and clinicians. METHODS: Part 1 of this study includes a pragmatic randomized controlled trial among patients (N=234) with early signs of knee OA in general practice and a BMI =25 kg/m2 with a follow-up of 24 months. Participants are randomized to either a lifestyle intervention program + usual care or usual care alone. Measurements include 3-monthly questionnaires, a physical examination at baseline and 24 months of follow-up (including collection of blood and urine samples) and magnetic resonance imaging of the knee at baseline and 24 months of follow-up. Primary outcomes (24 months): 1. Mechanistic outcome: 5kg or 5% weight reduction; 2. Clinical progression of knee OA; 3. Structural progression on MRI; 4. Societal costs and 5. Quality of life. Intention-to-treat analyses will serve as primary analyses and effects will be estimated using multilevel longitudinal regression methods. Part 2 consists of a qualitative study among health care professionals and patients. To investigate potential barriers and facilitators for the implementation of the lifestyle intervention in primary care, and to investigate how well the intervention fits the needs and behaviours of patients and which individual and environmental determinants may influence the compliance to the intervention, semi-structured interviews will be held with health professionals and patients. The semi-structured interview topics are based on literature and the CFIR framework. A total of 20 to 30 health care professionals will be interviewed, depending on data saturation and 15 to 20 participants will be interviewed, also depending on the data saturation. Primary outcomes: 1. Barriers, facilitators and boundary conditions for the implementation of the lifestyle intervention in primary care for knee OA patients, experienced by health care professionals and patients; 2. Agreement of patients behaviour, wishes and expectations with the combined lifestyle intervention; 3. Individual and environmental determinants that impact the compliance to the intervention. FEASIBILITY: We will recruit patients in general practice, using our PRIMEUR network of 91 GPs in the large region of Rotterdam. This recruitment method was earlier successful in our preventive trial on knee OA. The ArtroseGezond platform for 14000 OA patients in the region enables us to communicate with OA patients and patients can show their interest in our study at the website. For the intervention, we will work closely together with HRC Rotterdam as this centre employs 10 certified lifestyle coaches that deliver the combined lifestyle intervention in the large region of Rotterdam (experience >300 patients). EXPERTISE: The study will be executed within the team of Asc/prof. M van Middelkoop and prof.dr. SMA Bierma-Zeinstra (chair in osteoarthritis and related disorders) at the Department of General Practice of the Erasmus MC University Medical Center Rotterdam, in close cooperation with the involved partners. The team has a huge amount of knowledge on OA, evaluations using randomized controlled trial designs, economic evaluations, qualitative research techniques and weight loss and lifestyle interventions.