FACTORS RELATED TO PATIENT ADHERENCE TO ANTIDIABETIC DRUG THERAPY

The objective of the present study was to assess patient adherence to antidiabetic drug therapy and its association with factors related to the patient, patient-provider relationship, therapeutic regimen and the disease itself. The study comprised 46 diabetic patients enrolled in a research and extension education center in the State of Sao Paulo, southeastern Brazil, in 2007. Data was collected through interviews using a questionnaire and the Treatment Adherence Measure (TAM). The patient adherence level to antidiabetic drug therapy was 78.3%. In conclusion, since prevalence of adherence is below that recommended in the literature, and in the light of poor blood glucose control and alleged failure of therapeutic regimen, health providers are urged to measure diabetic patient treatment adherence, because it is key to adequate diabetes management with drugs.

The objective of the present study was to assess patient adherence to antidiabetic drug therapy and its association with factors related to the patient, patient-provider relationship, therapeutic regimen and the disease itself.The study comprised 46 diabetic patients enrolled in a research and extension education center in the State of Sao Paulo, southeastern Brazil, in 2007.Data was collected through interviews using a questionnaire and the Treatment Adherence Measure (TAM).The patient adherence level to antidiabetic drug therapy was 78.3%.In conclusion, since prevalence of adherence is below that recommended in the literature, and in the light of poor blood glucose control and alleged failure of therapeutic regimen, health providers are urged to measure diabetic patient treatment adherence, because it is key to adequate diabetes management with drugs.
Several studies investigating adherence to chronic disease treatment have evidenced that patients often discontinue their medications or even do not take them at all because they consider them ineffective or experience untoward side effects (2)(3)(4) .Among diabetes patients, many believe they do not need any drug therapies as they have no symptoms.
Different definitions of adherence have been proposed but it is generally defined as no less than 80% use of prescribed drugs and other procedures, as well as compliance with doses, times, and treatment duration.It represents the final step of a proposed rational drug use (3,5) .
M a n y f a c t o r s c a n a f f e c t t r e a t m e n t adherence and there is no consensus on which has the greatest impact.First, it should be considered whether patients have access to drugs.Ruling out the possibility of no access, patient adherence to drug therapy can be divided into four groups of factors: patient-related; related to patient-provider relationship, therapeutic regimen, and the disease itself (1,3) .
A complex variety of determinants clearly plays a role in patient adherence to the therapeutic regimen and contributes to non-adherence of those with chronic conditions like diabetes.
There is a lack of studies investigating adherence to antidiabetic drug therapy, and those available have different designs and inconsistent results.Further investigation is needed as most studies have focused on patient adherence to antihypertensive and lipid-reducing drugs instead of to oral antidiabetic agents and insulin (4,(6)(7) .
Researchers and health providers have recently been devoting a great deal of effort to better understand non-adherence to drug therapy.
It is though a challenge as people's behaviors involve complex mechanisms.There is a need to further explore this issue in order to identify behaviors that facilitate and/or prevent adherence to drug therapy.

OBJECTIVE
To assess patient adherence to antidiabetic drug therapy and to describe its association to factors related to the patient, patient-provider relationship, therapeutic regimen, and the disease itself.proving to be a good instrument for capturing a v a r i e t y o f b e h a v i o r s i n v o l v e d i n t r e a t m e n t adherence (8) .

MATERIALS AND METHODS
A literature search did not find any studies on the applicability of TAM instrument in Brazilian subjects.But given the closeness between European

RESULTS
Of 46 (100%) subjects studied, 78.3% were adherent and 21.7% were non-adherent to drug therapy.Table 1 shows the prevalence of patient adherence to drug therapy according to factors related to the patient, patient-provider r e l a t i o n s h i p , t h e r a p e u t i c r e g i m e n , a n d t h e disease itself.Although different prevalences of adherence were found for each factor studied, these differences were not statistically significant (p>0.05) in Fisher's exact test, as shown in Table 1.

DISCUSSION
The prevalence of patient adherence to drug therapy for diabetes management found in the study was 78.3%.It is similar to that described in diabetes patients receiving drug therapy, 79.7% (9) .Another study showed 95.7% prevalence of adherence to antihyperglycemic agents in type 2 diabetic patients (4) .
As for patient-related factors associated to adherence to drug therapy, higher adherence among men than women could be explained by the fact that women are more prone to stress and to develop mental health conditions.Thus, emotional disorders like depression can be associated with non-adherence to drug therapy (10) .
Data on age is consistent with the literature; chronic patients' age affects adherence to drug therapy, as lower adherence was seen among younger patients (11) .
In regard to schooling, more educated patients were more adherent to therapy.Low schooling makes learning more difficult; as diabetes drug therapy gets more complex, patients are required to have more complex cognitive skills to be able to understand the prescribed drug therapy and to adhere to treatment for good glucose control.
As for family income, the study data corroborates the findings of another study that reported that those with family income less than five MMWs showed lower adherence when compared to those with higher income (9) .
As for factors related to the patient-provider relationship, the present study showed that patients' knowledge on diabetes and the proposed treatment directly influences their adherence to drug therapy.
Patients' perception of the expected treatment benefits increases their adherence.However, it was verified that health providers rarely assess patient knowledge as part of their clinical routine (7) .
Treatment adherence is a complex phenomenon influenced by multiple determinants.The patients' beliefs on drugs may be the key for their adherence to drug therapy, as they often choose to take a drug or not based on information they have about them.
A study reported that 82% of the diabetic patients studied believed the prescribed drugs would relieve their symptoms and 83% believed they would protect their health in the future.These subjects had higher adherence rates to drug therapy than those who distrusted it (98.5 and 87%, respectively) (4) .
It is crucial that patients are actively involved in drug therapy choice.When patients are involved

Factors
related to patient adherence to antidiabetic… Gimenes HT, Zanetti ML, Haas VJ Rev Latino-am Enfermagem 2009 janeiro-fevereiro; 17(1):46-51 www.eerp.usp.br/rlae-the instrument's original language -and Brazilian Portuguese and the fact that different cultural b a c k g r o u n d s d o n o t h a v e a n e f f e c t o n t h e instrument items, it was first translated from European into Brazilian Portuguese.It was then reviewed by three diabetes specialists and checked for item intelligibility, easy reading comprehension and presentation format, which were deemed adequate for the purposes of the study.A pilot study was carried out with five patients at the study site and the instrument proved to be adequate for administration in the study.After subjects' consent, data were collected at the study site through guided interviews that lasted on average 30 minutes.Patients were addressed upon their arrival at the center and individually interviewed in a private room by a single interviewer.Medical records as well as diabetes test results of all subjects were reviewed.The analysis of TAM items was based on answers rated on a Likert-type scale for each question (always (1); almost always (2); frequently (3); sometimes (4); rarely (5); and never (6)).Scores for each TAM question were added up and divided by the total number of questions and then dichotomized as adherent or non-adherent to drug therapy.Univariate and bivariate analyses were conducted using absolute and relative frequencies and 2x2 contingency tables.Fisher's exact test was performed to assess the association between adherence and factors related to the patient, patient-provider relationship, therapeutic regimen, and the disease itself.It was opted for this test because of the small sample size and the expected result frequency (lower than five in all associations studied).A 5% significance level was set.The study was approved by the Research Ethics Committee at the University of São Paulo at Ribeirão Preto College of Nursing (Protocol No. 0541/2005).

Table 1 -
Prevalence of adherence to antidiabetic drug therapy according to factors related to the patient, patient-provider relationship, therapeutic regimen, and the disease itself.Ribeirão Preto,Brazil, 2007 1Variables were dichotomized for Fisher's exact test; 2 "Do not know" and "Unknown" answers were considered missing information to perform Fisher's exact test