The Effect of Nonadherence with Oral
Hypoglycemics on Potentially Avoidable
Hospitalizations among Medicare Part D Enrollees
with Diabetes
AcademyHealth 2009
Yi Yang MD PhD, Vennela Thumula BS,
Patrick Pace PhD, Benjamin Banahan III PhD,
Noel Wilkin RPh PhD, William Lobb RPh PhD
The University of Mississippi School of Pharmacy
Department of Pharmacy Administration
Introduction
 In the US, approximately 9.3% of adults aged 20 years or older
(19.3 Million, 2002 U.S. population) have diabetes mellitus1
 The estimated total cost for diabetes, including direct medical
care costs and lost productivity costs, reached $174 billion in
20072
 Clinical trials and epidemiological studies have demonstrated
intensive glycemic control is associated with a significant
reduction in microvascular and macrovascular
complications3,4
 Though there are many factors contributing to successful
glycemic control, pharmacologic therapy with oral
hypoglycemic (OHG) agents plays an important role3,4
2
Introduction (cont)
 Diabetes is a chronic disorder. Patients must follow
the prescribed treatment regimen for as long as the
disorder persists
 Medication nonadherence among patients with
diabetes has been reported to be as high as 64% and
this may be a contributing factor in patients’ failing
to achieve therapeutic goals and having adverse
health outcomes5-7
3
Introduction (cont)
 In 2007, AHRQ revised Prevention Quality Indicators
(PQIs) for ambulatory care-sensitive conditions, such
as diabetes and congestive heart failure, for which
timely and effective ambulatory care can potentially
prevent the need for hospitalizations8
 The PQIs were designed to be used with hospital
inpatient data to identify potentially avoidable
hospitalizations (PAHs) among patients with
ambulatory care-sensitive conditions
4
Introduction (cont)
 PQIs for diabetes include
o
o
o
o
Diabetes short-tem complications admission rate
Diabetes long-term complications admission rate
Uncontrolled diabetes admission rate
Rate of lower-extremity amputation among patients with
diabetes
 However, there have been relatively few studies that
have examined PQIs in diabetes
5
Objective
 To examine the effect of nonadherence with
OHGs on subsequent PAHs among Medicare
Part D enrollees with diabetes who were
receiving OHG therapy
6
Funding
 The work reported was conducted as part of a
contract titled “8th SOW 1d3 QIO Intervention and
Support Work Using Integrated Data,” which was
supported through a sub-contract with Information
and Quality Healthcare, Inc. (IQH) as part of the
Centers for Medicare and Medicaid Services (CMS)
quality improvement and intervention activities. The
views expressed are those of the authors and do not
necessarily reflect those of CMS, IQH, or the
University of Mississippi
7
METHODS
8
Methods: Study Period
Patient Identification
01/01/2006
06/30/2006
10/01/2005
03/31/2007
Adherence Measurement
Outcome Measurement
9
Methods: Patient Inclusion Criteria
 Medicare Part D enrollees from six states (AL, CA, FL, MS, NY, and
OH)
 Continuous Medicare enrollment from 10/01/2005 to 03/31/2007
 Had a diagnosis of diabetes
o At least one ICD-9 in Medicare Medical Claims data (10/01/2005-06/30/2006);
or
o At least one claim of insulin (>=10ml total) in Part D data (01/01/200606/30/2006); or
o Two or more claims for any OHG in Part D data (01/01/2006-06/30/2006); or
o At least one claim for over 30-day supply of OHG in Medicare Part D Claims data
(01/01/2006-06/30/2006)
 Had at least one filled prescription for any OHG during the first six
months in 2006
10
Methods: Patient Exclusion Criteria
 Medicare Part D claims with missing data for
service date or product service code
 Without any Part A or B claims from
10/01/2005 to 03/31/2007
11
Methods: Adherence
 Adherence to OHG was measured using
proportion of days covered (PDC)
o PDC=Number of Days of with Medication onhand/Number of Days in the Specified Time
Interval
 Optimal adherence was defined as
achievement of a PDC≥80%, poor adherence
was defined as 50%≤PDC < 80%, and very poor
adherence was defined as 0% ≤ PDC < 50%
12
Methods: Outcome Measures
 The outcome studied was any PAH during the
follow-up period (07/01/2006 - 03/31/2007)
o Hospitalization data was obtained from Medicare
Part A claims
o The outcome measure was dichotomized as
having PAH or not
13
Methods: Analysis
 Multivariate logistic regressions were used to
estimate association between optimal
adherence, poor adherence, and very poor
adherence and PAH while controlling for:
o Patient baseline demographics (age, gender, race)
o Baseline comorbidities (Deyo-adapted Charlson
Comorbidity Index, CCI)
14
RESULTS
15
Results: Patient Characteristics
Optimal
Adherent
(n=714,867)
Poor Adherent
(n=122,888)
Very Poor
Adherent
(n=263,778)
64.9%
11.2%
24.0%
72.0 (10.1)
71.1 (10.9)
70.7 (11.5)
Females
57.9%
61.2%
58.7%
White
67.7%
58.7%
63.6%
Black
14.5%
20.4%
19.0%
Hispanic
7.5%
10.9%
8.7%
Other
10.3%
10.0%
8.8%
0.93 (1.8)
1.1 (1.9)
1.4 (2.2)
Patient characteristics
(N=1,101,533)
%
Age, mean (SD), yr
Gender
Race
CCI, Mean (SD)
16
Results: PAHs
 52,176 (4.74%) patients had at least one PAHs
o 1,540 had PAH due to diabetes short-term
complications
o 31,179 had PAH due to diabetes long-term
complications
o 22,205 had PAH due to uncontrolled diabetes
o Only 37 patients had PAH due to diabetes-related
lower-extremity amputation
17
Results: Multivariate Logistic Regressions
Patient Characteristics
Adherence
Gender
Age
Race
Odds Ratio
95% CI
p-value
Poor adherence
1.226
1.192-1.261
<.001
Very poor adherence
1.188
1.164-1.212
<.001
Females
1.195
1.173-1.218
<.001
<65
1.826
1.782-1.870
<.001
≥75
1.136
1.113-1.161
<.001
Black
1.326
1.296-1.357
<.001
Hispanic
1.390
1.348-1.433
<.001
Other
0.972
0.939-1.007
.1128
1.320
1.316-1.324
<.001
CCI (1 unit increase)
18
Conclusions
 Overall, nonadherence to OHG is common
among Medicare Part D enrollees with
diabetes who were receiving OHG therapy
 Nonadherence to OHG is associated with
increased risks for PAHs
19
Implications
 Given the prevalence of nonadherence and the
significant association between nonadherence and
PAH, there is certainly a need to identify strategies to
improve patient adherence with prescribed
medications
 Healthcare professionals may play an important role
in identifying nonadherent patients and initiate
interventions to improve patient adherence
20
Limitations




Given the chronic nature of diabetes, it is very likely that most patients were
chronic medication users and had started OHG therapy long before the study
started. The observed PAHs probably reflect the cumulative effect of medication
nonadherence over an extended period of time. However, from the Medicare Part
D data, we were unable to identify exactly when the patient started OHG therapy
From Part D data we used in this study, we were also unable to determine
whether the patient actually took the medication or not once dispensed
The observed associations between poor adherence and PAH could be due to
unmeasured covariates, such as the “healthy adherer” effect
Our study sample consisted of a relatively large population of Medicare Part D
enrollees with diabetes who were receiving OHG therapy. The associations
between nonadherence and outcome have been amplified
21
References
1. Cowie CC, Rust KF, Byrd-Holt DD, Eberhardt MS, Flegal KM, Engelgau MM et al. Prevalence of diabetes and
impaired fasting glucose in adults in the U.S. population: National Health And Nutrition Examination Survey
1999-2002. Diabetes Care. 2006; 29(6):1263-1268.
2. National Institute of Diabetes and Digestive and Kidney Diseases. National Diabetes Statistics, 2007 fact
sheet. 2008. Bethesda, MD, U.S. Department of Health and Human Services, National Institutes of Health.
3. Adler AI, Stratton IM, Neil HA, Yudkin JS, Matthews DR, Cull CA et al. Association of systolic blood pressure
with macrovascular and microvascular complications of type 2 diabetes (UKPDS 36): prospective
observational study. BMJ. 2000; 321(7258):412-419.
4. Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and
risk of complications in patients with type 2 diabetes (UKPDS 33). UK Prospective Diabetes Study (UKPDS)
Group. Lancet. 1998; 352(9131):837-853.
5. Cramer JA. A systematic review of adherence with medications for diabetes. Diabetes Care. 2004;
27(5):1218-1224.
6. Lerman I. Adherence to treatment: the key for avoiding long-term complications of diabetes. Arch Med
Res. 2005; 36(3):300-306.
7. Rubin RR. Adherence to pharmacologic therapy in patients with type 2 diabetes mellitus. Am J Med. 2005;
118 Suppl 5A:27S-34S.
8. AHRQ. Guide to Prevention Quality Indicators. Available at:
http://www.qualityindicators.ahrq.gov/downloads/pqi/pqi_guide_v31.pdf
22