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THOMSON SCIENTIFIC & HEALTHCARE
ISPOR 11th Annual International Meeting This study was funded by Pfizer, Inc.May 24, 2006
The Effects of Statin (HMG-CoA Reductase
Inhibitor) Copayments and Statin Adherence on
Medical Care and ExpendituresTeresa B. Gibson1, Ph.D.; Tami L. Mark1 Ph.D., MBA; Kirsten Axelsen2, MS; Joan A. Mackell2, Ph.D.; Heidi King2, MS; Onur Baser1, Ph.D.; Kimberly A. McGuigan2, Ph.D., MBA
1 Thomson Medstat, Ann Arbor, MI2 Pfizer, Inc., New York, NY
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Introduction
• HMG-CoA reductase inhibitor (“statin”) therapy is a widely accepted treatment for patients with high cholesterol.
• Clinical trials report benefits such as reductions in mortality and morbidity from statin therapy (e.g., National Cholesterol Education
Program(NCEP) Expert Panel 2002, and Simes et al. 2002).
• The extent of cardiovascular risk reduction can increase in proportion to the amount of time on statin therapy (Simes et al. 2002)
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Introduction (continued)
• Prescription drug copayments have increased as employers and other plan managers attempt to contain prescription drug costs. (Kaiser Family Foundation and the Health Research and Educational Trust 2005)
• Cost-sharing is likely to continue to rise. Many firms intend to continue to increase cost-sharing in the near future. (Kaiser Family Foundation and the Health Research and Educational Trust 2005; PriceWaterhouseCoopers 2005)
• Higher prescription drug copayments may lead patients with chronic conditions to reduce utilization of maintenance drugs (Bierman and Bell 2004; Gibson et al. 2005)
• Higher statin copayments are associated with a reduction in compliance for new users of statins. Higher statin copayments and lower levels of statin compliance are also related to lower levels of outcomes (e.g., LDL-C goal attainment and hospitalization). (Goldman et al. 2005, Schultz et al. 2005)
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Study Aims
1. To estimate the effects of statin copayments on statin adherence for statin users, and,
2. To estimate the effects of statin adherence on expenditures and utilization
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Data Source
• MarketScan Commercial Claims and Encounter Database and Medicare Supplemental and Coordination of Benefits Database for services provided from January 1, 2000 through December 31, 2003.
– Contains the healthcare experience of individuals with employer-sponsored health care insurance and Medicare supplemental insurance in the United States
– Includes enrollment information and inpatient, outpatient and pharmacy claims
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Inclusion Criteria and Study Sample
• Inclusion Criteria:– 18 years of age or older
– Continuously-enrolled from 2000 through 2003
– At least one statin prescription fill January 2001 through June 2001
– No indication of pregnancy during the study time frame
• Study Sample Construction:– Continuing users: Filled a statin prescription in 2000
– New Users: Filled a statin prescription in Jan-June 2001 and at least one year prior without a statin fill
– Each patient was followed July 2001 through December 2003
• Continuing Users: n=93,296 patients
• New Users: n=24,113
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Measures• Adherence to Statin Therapy (July 2001 – December 2002)
– Medication Possession Ratio (MPR) calculated by assessing whether statins were on-hand each day, % of days with statins on-hand
– Adherent if MPR > 80%
• Expenditures and Utilization (January - December 2003)– Expenditures –
• Total (Medical plus prescription drug)• Medical• Prescription Drug
– Utilization (1/0 variables)• Physician Office Visit• Emergency Room Visit• Hospitalization• Coronary Heart Disease-related (CHD) Hospitalization
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Explanatory Variables
• Patient Cost-Sharing– Statin cost sharing amount (USD $ 2003 per day) – Office Visit cost sharing amount (USD $ 2003 per visit)
• Sociodemographic - Age, Gender, US Census Region, Urban Area, Household Income and % with College Degree (by ZIP code via Census information)
• Health Plan Type – (e.g., HMO, PPO, POS, Comprehensive)
• Type of Provider (prior 12 months)
• Medication (prior 12 months) - Number of prescriptions, Any use of mail order
• Severity/Comorbidity (prior 12 months)– Acute Myocardial Infarction, Angioplasty, Coronary Bypass Surgery, Chronic
Ischemic Heart Disease (IHD), Coronary Atherosclerosis, Other IHD, Hypertension– Anxiety, Dementia, Depression
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Multivariate Analysis-Two Stage Residual Inclusion
Stage 1: Adherence, Logistic Regression
• Pr(Adherencei|x) = F(0 + 1sociodemographici + 2plani + 3providerip + 4medicationip + 5severityip + 6comorbidityip + 7cost-sharingi)
Stage 2: Utilization and Expenditures
• G(Expenditurei) = ln(0 + 1sociodemographici + 2plani + 3providerip + 4severityip + 5comorbidityip + 6Adherence + 7 û1 )
• P(Utilizationi|x) = F(0 + 1sociodemographici + 2plani + 3providerip + 4severityip + 5comorbidityip + 6Adherence + 7 û1)
i is patient, p is a 12 month lag, F is the cumulative logistic function and G is the gamma distribution
^
ν
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Selected CharacteristicsContinuing Users New Users
Characteristic n=93,296 n=24,113
Female (%) 44.5 50.2
Age (y) 64.1 11.2 58.8 12.6
Insurance Plan Type (%)
Comprehensive 28.9 26.2
HMO 3.2 3.9
Capitated POS 33.0 26.3
Non-Capitated POS/EPO 6.4 8.5
Preferred Provider Org. 28.8 35.1
Statin Copayment ($/day) $0.40 0.20 $0.43 0.17
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Selected Characteristics (continued)Continuing Users New Users
Characteristic (%) (12 month lag)
n=93,296 n=24,113
AMI 1.6 1.4
Angina 18.9 17.8
CABG 0.9 0.7
Chronic IHD 5.0 2.9
Coronary Atherosclerosis
24.8 15.3
Other IHD 3.4 2.5
PCTA 0.6 0.5
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Measures of Adherence, Utilization and ExpenditureMeasure n=93,296 n=24,113
Adherence/MPR (July 2001-Dec 2002)
0.58 0.49 0.28 0.45
Utilization and Expenditures (2003)
Total Expenditures $6,589.70 7893.24 $5,798.63 8485.10
Medical Expenditures $3,513.53 6866.97 $3,323.55 7438.78
Prescription Drug Expenditures $3,076.17 2598.15 $2,475.08 2767.20
Office Visits 0.93 0.26 0.90 0.30
ER Visits 0.22 0.41 0.21 0.41
Hospitalizations 0.14 0.35 0.12 0.32
CHD-Related Hospitalizations 0.05 0.23 0.04 0.20
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Effects of Copayments on Adherence-Continuing Users
54
55
56
57
58
59
60
61
LowCopayment($.19/day)
MediumCopayment
($.42)
HighCopayment
($.63)
Pre
dic
ted
Pro
bab
ility
of
Ad
her
enceSelected
EffectsAdjusted Odds Ratio 95% CI
Female (0.863, 0.914)
Age, y <=65 (1.025, 1.03)
Age, y over 65 (0.982, 0.988)
Statin Copayment
(0.632, 0.735)
Higher copayments are associated with lower levels of adherence
All p<.01, n=93,296
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Effects of Copayments on Adherence-New Users
24
25
26
27
28
29
30
31
LowCopayment($.19/day)
MediumCopayment
($.42)
HighCopayment
($.63)
Pre
dic
ted
Pro
bab
ility
of
Ad
her
enceSelected
EffectsAdjusted Odds Ratio 95% CI
Female (0.717, 0.813)
Age, y <=65 (1.03, 1.04)
Age, y over 65 (0.962, 0.976)
Statin Copayment
(0.621, 0.918)
Higher copayments are associated with lower levels of adherence
All p<.01, n=24,113
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Effects of Adherence on ExpendituresContinuing Users
Expenditures Coefficient Standard Error p-value
Total Expenditures 0.179 0.117 0.125
Medical Expenditures
-0.256 0.199 0.197
Prescription Drug Expenditures
0.703*** 0.069 0.000
Higher levels of adherence are associated with higher prescription drug expenditures, lower (nonsignificant) medical expenditures and no change in total medical expenditures.
* p<.10,** p<.05, *** p<.01
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Effects of Adherence on ExpendituresNew Users
Expenditures Coefficient Standard Error p-value
Total Expenditures -0.088 0.109 0.423
Medical Expenditures
-0.150 0.179 0.402
Prescription Drug Expenditures
0.065 0.081 0.426
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Effects of Adherence on Utilization – Continuing Users
Coefficient Adjusted Odds Ratio 95% CI
Office Visits 0.349 (0.688, 2.876)
ER Visits -1.514*** (0.133, 0.364)
Hospitalizations -.566* (0.308, 1.048)
CHD-Related Hospitalizations
-1.688*** (0.072, 0.480)
* p<.10,** p<.05, *** p<.01
Higher levels of adherence are associated with a decreased likelihood of ERvisits, hospitalizations and CHD-related hospitalizations
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Effects of Adherence on Utilization – New Users
Coefficient Adjusted Odds Ratio 95% CI
Office Visits 0.927** (1.228, 5.195)
ER Visits 0.059 (0.648, 1.737)
Hospitalizations -0.076 (0.497, 1.729)
CHD-Related Hospitalizations
-0.882* (0.158, 1.082)
* p<.10,** p<.05, *** p<.01
Higher levels of adherence are associated with an increased likelihood of an office visit, no change in ER visits or hospitalizations and a decreased likelihood of CHD-related hospitalizations
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Effects of Adherence on Utilization – Continuing Users
0
0.2
0.4
0.6
0.8
1
Physician OfficeVisits
ER Visits Hospitalization CHD-RelatedHospitalization
25% Adherent Adherent
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Effects of Adherence on Utilization – New Users
0
0.2
0.4
0.6
0.8
1
Physician OfficeVisits
ER Visits Hospitalization CHD-RelatedHospitalization
25% Adherent Adherent
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Limitations
• Administrative Data
• Continuously-enrolled population with employer-sponsored insurance
• Selection
• Sensitivity Analysis
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Summary and Conclusions
• In this large cohort of statin users enrolled in employer-sponsored plans, prescription drug copayments are a financial barrier to statin adherence.
• For continuing/prevalent users of statins, statin adherence is related to higher prescription drug expenditures and a nonsignificant offset in medical expenditures. Total expenditures are not significantly different.
• For new/incident users of statins, statin adherence is not associated with changes in medical or prescription drug expenditures.
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Summary and Conclusions
• For continuing users of statins, lower statin copayments are associated with higher levels of statin adherence. Total costs may not change, but fewer negative events (ER visits, hospitalizations and CHD-related hospitalizations) occur.
• Reducing patient cost-sharing for a maintenance drug regime may be an effective intervention.