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Assessing the Association Between Medication Adherence and Glycemic Control

Among a population of adult patients with type 2 diabetes, adherence to oral hypoglycemic medications is independently associated with poor glycemic control, even after adjusting for patient-level covariates.
Published Online: Jun 13,2017
David M. Mosen, PhD, MPH; Harry Glauber, MB, BCh; Ashley B. Stoneburner, MPH; and Adrianne C. Feldstein, MD, MS

ABSTRACT

Objectives: We studied the independent association of adher- ence to oral hypoglycemic medications with poor glycemic con- trol among a population of adults with type 2 diabetes (T2D), adjusting for demographics, health behaviors, and clinical and treatment characteristics.

Study Design: This was a retrospective cohort design.

Methods: We studied a population of Kaiser Permanente Northwest (KPNW) members with T2D who either had: 1) good glycemic control (glycated hemoglobin [A1C] <8.0%; n = 15,891) or 2) poor glycemic control (A1C >9.0%; n = 3709). The primary independent variable was medication adherence to 1 or more oral hypoglycemic medications. High medication adherence was defined as at least 80% of days covered in the 12 months prior to the A1C test date (yes vs no). Multiple logistic regression was used to analyze the independent association of medication adherence with poor glycemic control, adjusting for demographics, health behaviors, medical comorbidities, healthcare utilization, receipt of diabetes care management services, and intensity of diabetes treatments. All measures were constructed via KPNW’s electronic heath record.

Results: Increased adherence to oral hypoglycemic medications was associated with a lower likelihood (OR, 0.54; 95% CI, 0.50-0.59; P <.0001) of having poor glycemic control, after adjusting for demographics, health behaviors, comorbidities, healthcare utilization, receipt of diabetes care management services, and intensity of diabetes treatments.

Conclusions: Higher adherence to oral hypoglycemic medica- tions is independently associated with a lower likelihood of having poor glycemic control among an adult population with T2D. Studies of the effects of measures to improve medication adherence on population-level glycemic control are needed.

Am J Pharm Benefits. 2017;9(3):82-88

 


Type 2 diabetes (T2D) is a chronic, progressive condition characterized by the failure of insulin secretion to compensate for resistance to insulin’s actions, resulting in hyperglycemia. The long-term complications of diabetes contribute to its status as a leading cause of premature illness and mortality.1 In 2012, 29.1 million individuals in the United States had diabetes (approximately 90% of the patients had T2D), and the prevalence appears to have increased in the past 2 decades.2 In 2012, diabetes resulted in $245 billion in costs, including $176 billion in direct medical costs and $69 billion in reduced productivity.3

The long-term control of hyperglycemia is essential in order to improve health outcomes for populations with diabetes. Poor glycemic control has been associated with microvascular complications4-6 and mortality,7,8 whereas good control reduces the development of microvascular and long-term cardiovascular complications.9 Current clinical guidelines to manage glycemic control utilize glycated hemoglobin (A1C) target levels, with adjustment for age and length of illness10; however, A1C levels greater than 75 mmol/mol (9.0%) are universally considered to reflect poor control.11 Of particular concern, according to data from a recent National Health and Nutrition Examination Survey, the proportion of adults with diabetes with poor glycemic control (A1C >9.0%) increased from 17.9% in the 2005-to-2008 period to 21.0% in the 2009-to-2012 period.12

Despite clinical evidence of the efficacy of several glucose- lowering medications, adherence levels often remain sub- optimal.13-17 Moreover, several studies have found that lower medication adherence can be associated with poorer glycemic control outcomes.14,18-23 However, these studies have several limitations, including small sample sizes and analyses not conducted on a population level.24,25

With this background, the primary objective of this study was to analyze the independent association of adherence to oral hypoglycemic medications with poor glycemic control among adults with T2D on a population level. Such research has significant clinical implications—given that medication adherence is a potentially modifiable factor—that may be influenced by quality improvement initiatives. A secondary objective was to identify demographics, health behaviors, comorbidities, healthcare utilization, diabetes care management services, and treatment intensity mea- sures associated with poor glycemic control, with an emphasis on factors that were modifiable.




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