1. Preliminary findings from POHEM-OA: BMI interventions STAR Meeting in Ottawa, ON July 7-8, 2010 By Eric C. Sayre 1

2. Abbreviations OA=osteoarthritis SROA=self-reported OA BMI=body mass index HUI=Health Utilities Index Mark 3 HALE=health-adjusted life years HRQoL=health-related quality of life CCHS=Canadian Community Health Survey POHEM-OA=Population Health Model for OA 2

3. BMI, OA and HRQoL Higher BMI increases rates of OA and directly decreases HRQoL (HUI/HALE) OA also decreases HRQoL POHEM-OA begins with age 20+ 2001 CCHS values of age, BMI and HUI, with baseline SROA->baseline OA stage in POHEM-OA POHEM-OA includes a trend model that increases mean BMI over time 3

4. BMI, OA and HRQoL BMI categories in POHEM-OA – Underweight (<18.5) – Normal weight (<25.0) – Overweight (<30.0) – Obese (>=30) OA stages in POHEM-OA – No OA – OA – 1-k visits to surgeon – 1-4 joint replacement surgeries 4

5. Intervention: Lower BMI POHEM-OA allows us to – Lower BMI in 2001 for everyone in-scope in 2001 but not new births/immigrants after 2001 – Lower BMI every year by some amount but this puts everyone in underweight by 2031 Study closed population and intervene in 2001 only: lowering 2001 BMI by 5 if BMI>=25 BMI trend model remains active; effect on BMI is constant 5

6. POHEM-OA Models Hazard ratios for BMI->OA Coefficients for BMI->HUI Not applicable since applied on transition as difference of coefficients 6 BMI<18.5BMI<25.0BMI<30BMI>=30 Female0.3311.762.03 Male1.5*10 -10 11.071.69 BMI<18.5BMI<25.0BMI<30BMI>=30 Female0.04710.07700.06230 Male-0.02650.01790.03120

7. POHEM-OA Models Incident OA->HUI (detrimental) ΔHUI=-0.1037*NewOA-0.0408*Male Last visit to surgeon->HUI (detrimental) HUI=0.2828-0.1171*Male+ 0.2988*(age<60)+ 0.2625*(ageЄ[60,70))+0.1897*(ageЄ[70,80))+ Normal(0,0.2803 2 ) Surgery->HUI (beneficial) ΔHUI=0.6971-.5447*PreviousHUI-.0027*Age 7

8. Results 20012031Delta N22,483,40014,317,129-8,166,271 Average age45.89 (45.79, 45.99) 67.43 (67.37, 67.50) 21.54 8 Intervals represent Monte Carlo error only

9. Results 9 2001 Base case 2001 Intervention 2001 Delta 2031 Base case 2031 Intervention 2031 Delta Average BMI25.55 (25.53, 25.58) 23.12 (23.1, 23.14) -2.4327.79 (27.75, 27.82) 25.56 (25.53, 25.58) -2.23 Proportion obese 14.99% (14.77, 15.20) 3.81% (3.64, 3.98) -11.18%26.82% (26.6, 27.04) 11.57% (11.4, 11.74) -15.25% Proportion overweight 33.66% (33.38, 33.94) 11.18% (10.96, 11.39) -22.48%37.15% (36.97, 37.33) 38.19% (38.01, 38.36) 1.04% OA incidence /1000py 7.42 (7.35, 7.49) 6.31 (6.23, 6.38) -1.1121.03 (20.89, 21.16) 19.29 (19.16, 19.42) -1.74 OA prevalence12.23% (12.00, 12.46) 12.13% (11.91, 12.36) -0.10%33.11% (32.98, 33.25) 30.69% (30.55, 30.82) -2.42% Average HUI0.874 (0.872, 0.875) 0.874 (0.872, 0.875) 0.0000.752 (0.750, 0.753) 0.756 (0.754, 0.758) 0.004 py=Person-years Intervals represent Monte Carlo error only

10. Results 10 Base caseInterventionDelta HALE for 20 year-olds27.06 (26.92, 27.21) 27.14 (26.99, 27.28) 0.08 HALE for 40 year-olds24.71 (24.61, 24.80) 24.81 (24.72, 24.91) 0.10 HALE for 60 year-olds16.94 (16.81, 17.07) 17.00 (16.87, 17.12) 0.06 Intervals represent Monte Carlo error only

11. Summary 5-point targeted reduction in BMI in 2001 does by 2031 – Reduced OA incidence/prevalence – Limited benefit on HRQoL through OA – Large drop in % obese -> large direct benefit (not measured in current POHEM-OA) 11

12. Future improvements POHEM-OA/BMI Option for direct HRQoL benefits of reduced BMI (treat initial reduction as “transition”) Support for BMI interventions applicable to open populations (e.g., reduce BMI on entry, for pre-existing persons/births/immigrants) Account for additional sources of error, such as around parameter estimates Vary the magnitude/target of the intervention 12

13. Acknowledgments Jacek Kopec Bill Flanagan and Philippe Fines Behnam Sharif The STAR team 13