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

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

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 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

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

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

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 Female Male1.5* BMI<18.5BMI<25.0BMI<30BMI>=30 Female Male

POHEM-OA Models Incident OA->HUI (detrimental) ΔHUI= *NewOA *Male Last visit to surgeon->HUI (detrimental) HUI= *Male *(age<60) *(ageЄ[60,70)) *(ageЄ[70,80))+ Normal(0, ) Surgery->HUI (beneficial) ΔHUI= *PreviousHUI-.0027*Age 7

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

Results Base case 2001 Intervention 2001 Delta 2031 Base case 2031 Intervention 2031 Delta Average BMI25.55 (25.53, 25.58) (23.1, 23.14) (27.75, 27.82) (25.53, 25.58) Proportion obese 14.99% (14.77, 15.20) 3.81% (3.64, 3.98) %26.82% (26.6, 27.04) 11.57% (11.4, 11.74) % Proportion overweight 33.66% (33.38, 33.94) 11.18% (10.96, 11.39) %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) (20.89, 21.16) (19.16, 19.42) 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) (0.872, 0.875) (0.750, 0.753) (0.754, 0.758) py=Person-years Intervals represent Monte Carlo error only

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

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

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

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