Background/Purpose: Cost effectiveness analyses of arthritis interventions require utility measurements to evaluate their relative effectiveness.  Clinical guidelines for knee osteoarthritis (KOA) treatment include a substantial role for physical activity. Recognizing the importance of physical activity, there are federal recommendations for US adults that now include persons with arthritis.  To investigate if attainment of these guidelines translates into better health-related utility in adults with KOA, we analyzed data from the Osteoarthritis Initiative (OAI).

Methods: Physical activity was measured by accelerometers on 1154 OAI participants aged 49 to 84 years with radiographic KOA (KL grade ≥2 from central lab) in at least one knee at the 48 month follow-up visit.  Activity intensity was determined from established accelerometer cutpoints for moderate-to-vigorous [MV] intensity (counts ≥ 2020/minute).  Physical activity was classified as 1) inactive (no bouts of MV activity lasting 10 minutes over the week; 2) insufficient activity (bouts of MV activity/week < 150 minutes), or 3) met the 2008 Physical Activity Guidelines aerobic component (≥150 MV minutes/week acquired in bouts ≥10 minutes).  An SF6-D utility score (0=worst to 1=best possibility utility) was derived from participant responses to the SF-12 questionnaire collected at the 48 month visit.  The relationship of physical activity levels to average health utility controlled for demographics (age, gender, race, education, income), knee factors (KL grade, knee symptoms, WOMAC knee pain, knee injury history) and general health (BMI, comorbidity, depression, smoking, hip pain, ankle pain, foot pain) using multiple linear regression.

Results: Almost half (48%) of adults with KOA were inactive; another 40% failed to meet recommended Guidelines.  Average utility scores consistently increased with better levels of physical activity: 0.772 for inactive, 0.797 for insufficient and 0.835 for meeting guidelines groups (p trend<.0001).  To determine if higher physical activity levels consistently correspond to better health utility among people with similar demographics and measured health we examined utility differences controlling for these factors.  These results (Table) showed a strong cross-sectional relationship and a statistically significant linear trend.

	Differences in mean utility between physical activity levels adjusted for demographic, knee health and general health factors
Adjustment Factors n=1154	Insufficient vs Inactive(95% CI)	Meet Guideline vs Inactive (95% CI)	Trend Test
Unadjusted	0.025 (0.010, 0.040)	0.063 (0.039, 0.086)	p<.001
Demographic	0.020  (0.005, 0.036)	0.053 (0.029, 0.077)	p<.001
Demographic+ Knee+ General Health Factors	0.011 (-0.002, 0.024)	0.023 (0.003, 0.044)	p=.018

 

Conclusion: Despite known benefits of physical activity, most adults with KOA were inactive.  Inactive adults with KOA had significantly lower health-related utility levels than persons who were insufficiently active as well as those who met Guidelines. These findings show a strong relationship between greater physical levels and better health utility. These findings support interventions to improve health-related utility for adults with KA by increasing physical activity, even if recommended levels are not attained

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/relationship-of-physical-activity-with-health-utility-in-the-osteoarthritis-initiative/