Background:Lack of physical activity in individuals with knee OA has shown to be associated with increased cardiovascular risk and mortality. Consequently, physical activity is a potential target for interventions in knee OA. However, most of the available studies concerning physical activity in individuals with knee OA were performed in relatively old populations with an inactive lifestyle. It is unclear how previous results can be generalized to other populations with different lifestyle and physical activity habits.Objectives:To investigate if knee OA is associated with lower physical activity in a general middle-aged Dutch population. Furthermore, to investigate the association of physical activity with patient reported outcomes such as knee pain and function, and health-related quality of life in individuals with knee OA.Methods:We used cross-sectional data from the Netherlands Epidemiology of Obesity (NEO) study, in which participants aged 45-65 years were included. Clinical knee OA was defined using the ACR criteria. Structural knee OA was defined on MRI using the modified criteria by Hunter et al. in a random subset of 1,285 individuals of our study population.We assessed knee pain and function with the Knee injury and Osteoarthritis Score (KOOS), and health-related quality of life (HRQoL) with the Short Form (SF)-36. Physical activity (in Metabolic Equivalent of Task (MET) hours per week) was assessed using the Short Questionnaire to Assess Health-enhancing physical activity (SQUASH).We used linear regression analyses to investigate 1) the association of knee OA with physical activity, and 2) of physical activity with knee pain, function, and HRQoL in participants with clinical knee OA. All analyses were adjusted for age, sex, body mass index (BMI), ethnicity, educational level and comorbidities. To account for possible information bias, we performed a sensitivity analysis to assess the association between clinical knee OA and physical activity measured by an accelerometer in a random subset of 15% of the study population.Results:Of 6,212 participants, we observed clinical knee OA in 14%, and structural knee OA in 12%. The general population characteristics and median physical activity of our study population are presented in Table 1. In comparison to participants without knee OA, participants with clinical knee OA had on average 9.60 (95% CI 3.70;15.50) MET hours per week more total physical activity (Figure 1). Structural knee OA was associated with 3.97 (-7.82; 15.76) MET hours per week more physical activity, compared with no structural knee OA.Sensitivity analysis showed a weak positive association of clinical knee OA with physical activity measured by an accelerometer: 2.37 (-6.05; 10.80) MET hours per week more physical activity in participants with clinical knee OA, compared with participants without clinical knee OA.In the subpopulation of participants with clinical knee OA, physical activity was not associated with knee pain, function or HRQoL.Conclusion:Knee OA was not associated with lower physical activity in this middle-aged Dutch population. This contrasts previous findings and warrants caution when generalizing physical activity outcomes to other populations. Furthermore, it stresses the need of more insight in the barriers and facilitators of physical activity in the middle-aged population.Table 1.Characteristics of the NEO study populationAlln = 6,214No clinical knee OA86%Clinical knee OA14%General population characteristics Age (year)55.7 (6.0)55.4 (6.1)57.5 (5.0) Sex (% women)555467 BMI (kg/m2)26.3 (4.4)26.1 (4.3)27.6 (5.1) Comorbidities (% present)242332Physical activity Total^ (MET-hours per week)118.8 (76.8;155.0)118.4 (76.6;154.4)123.5 (77.8;157.2)Numbers represent mean (SD) or percentages. ^median (25th, 75th percentiles). Abbreviations: OA = osteoarthritis. BMI = Body Mass Index. MET = Metabolic Equivalent of Task.Disclosure of Interests:None declared
Physical activity vs. health related somatic features of middle-aged and elderly people