Effect of Sociodemographic Variables and Other Factors on the Usage of Different Doses of Aspirin in Postmyocardial Infarction Patients: A Cross-sectional Study.

BACKGROUND: Aspirin (acetylsalicylic acid) is commonly prescribed to patients with a history of myocardial infarction (MI) or occlusive vascular events (e.g., stroke). Due to the complications associated with failure to follow aspirin usage guidelines, determining predictors of aspirin noncompliance in these patient populations is of clinical value and may help prevent poor outcomes.
METHODS: This cross-sectional study of all patients with a previously diagnosed MI was conducted over a period of 3 months from May 2015 to July 2015 at a government-based hospital in Karachi, Pakistan. Patients were administered a questionnaire that comprised two parts. Part A was designed to measure sociodemographic data including age, gender, and marital status. Part B determined whether the patient was counseled on aspirin significance, and dosage recommendation, and was participating in cardiac rehabilitation therapy.
RESULTS: A total of 456 patients included in the study. Of them, 298 (66.7%) were males. The average age was 59 (standard deviation 11) years. The outcome from univariate logistic regression revealed that with 1 year increase of age, the usage of low dose of aspirin was significantly decreased by 2%. Patients with higher education attributed a significantly different effect on the usage of aspirin. Marital status divulged no significant association with the use of different doses of aspirin. The role of rehabilitation had no effect when adjusted for age and level of education.
CONCLUSION: Post-MI patients with higher education level and undergoing rehabilitative therapy are more likely to take low-dose aspirin as compared to those who failed to have these attributes. There is a need for carrying out further work to confirm these findings and expand our recommendations, particularly the sensitive issue regarding adequate doctor counseling among these high-risk patients.

INTRODUCTION

Low-dose aspirin (acetylsalicylic acid) is commonly prescribed to patients with a history of myocardial infarction (MI) or occlusive vascular events (e.g. stroke). The efficacy of aspirin in the secondary prevention of cardiovascular and cerebrovascular events has been well established.[123] This has subsequently led to the common practice of prescribing low-dose aspirin as a cornerstone of medical management of patients after their first event. Further support of this approach comes from data indicating that aspirin nonadherence or discontinuation is associated with an almost 3-fold risk of a major cardiac event.[4] Clinical guidelines in a meta-analysis of 50,279 patients by Biondi-Zoccai et al. showed that aspirin nonadherence or discontinuation is associated with an almost 3-fold increased risk of major adverse cardiac events (recurrence of MI/stroke).[4] Thus, aspirin is a standard treatment in patients for the secondary prevention of cardiovascular outcomes. Clinical guidelines recommend long-term (usually lifelong) administration in such patients.[56] However, several factors, such as daily usage and adverse effects, pose considerable compliance issues, with rates as high as fifty percentage.[7]

Nonadherence can decrease the quality of life and can significantly increase the cost of medical care.[8] More importantly, studies have shown that nonadherence is the chief reason for many preventative complications.[9] Many studies have focused and reported nonadherence regarding specific pharmacological treatment of different coronary risk factors, with statin nonadherence associated with elevated LDL levels being an example. However, few studies have examined compliance related to different doses of aspirin post-MI. Since nonadherence can nullify the effects of optimal medical management, understanding demographic variables that can predict potential issues with varying dosages of aspirin may help forestall preventable complications.

METHODS

This cross-sectional study was conducted over a period of 3 months from May 2015 to July 2015 at a government-based hospital in Karachi, Pakistan. Written informed consent was obtained from each participant, and all ethical considerations were met in accordance with the World Medical Association Declaration of Helsinki law.

All patients visiting the cardiology outpatient department with previously diagnosed MI were evaluated for the study with the exclusion criteria as follows: patients not prescribed aspirin; patients with contraindication to aspirin therapy, such as those with hemophilia and peptic ulcer disease; and patients with cognitive impairments. Using the methodology of Sud et al., a sample size of 375 patients was calculated to be necessary to determine significance of P < 0.05.[7] Accounting for nonrespondent bias and incomplete questionnaires, the sample size was increased to 456. Nonadherence was defined as failure to take prescribed dosages of aspirin for more than 2 days per week.

A precoded questionnaire was presented to the enrolled patients to ensure anonymity of response available in both English and Urdu languages, along with a double-blind system with the investigators to eliminate any potential bias. The principal investigator explained the nature and purpose of the study to all selected participants. Data were collected from randomly selected patients using survey methodology until the sample size was achieved. Confounder was managed through a randomized selection of participants. Data were collected from every consecutive person until the required numbers of patients were completed.

The questionnaire comprised two parts: Part A was designed to measure sociodemographic data including age, gender, and marital status and Part B determined whether the patient was counseled by the doctor on aspirin significance; whether the patient was on low doses (75 mg) or high doses (300 mg) of aspirin; and whether the patient was performing rehabilitation therapy. Uneducated patients were defined as all those patients who never went to school.

Statistical analysis

After entering data in IBM, statistical analyses were performed in SPSS version 21 (International Business Machines, Armonk, New York, USA) software. Since all variables were categorical, frequencies and percentages were computed as descriptive measures.

Mean with standard deviation (SD) was reported for continuous variables, i.e., age of the patients. Since age was found to be nonnormally distributed by Shapiro–Wilk test, Mann–Whitney U-test was run to compare age of the patients using the two aspirin dose. Chi-square test was carried out to assess association of categorical variables with aspirin dose. Univariate and multivariate logistical regression was run to measure effect of factors associated with the use of the two doses of aspirin. The threshold of significance was set at 0.05.

RESULTS

A total of 456 patients were included in the study. Of them, 298 (66.7%) were males [Table 1]. The average age was 59 (SD 11 years) years. A significant minority of patients met the criteria for “uneducated” (n = 162, 35.2%) [Table 1]. The frequency of married individuals was high (94.4%). Almost 71.1% of patients were taking low-dose aspirin per day. Rehabilitation programs were attended by 9.6% of patients. Counseling by doctors regarding aspirin side effects was given to 61.1% (n = 273) of patients [Table 1].

Table 1

Demographic variables (N values)

The univariate analysis revealed that patients taking low dose were significantly younger (P = 0.014) [Table 2]. No significant association of gender and marital status was found with intake of different doses of aspirin. Nearly 32.7% of uneducated patients consumed low dose. The frequency of rehabilitation was significantly lower among patients on low-dose aspirin (P = 0.013). About 65% of patients taking high-dose aspirin received doctor counseling versus 59.4% on low-dose aspirin. However, the association was insignificant in this regard (P = 0.265) [Table 2].

Table 2

Demographic vairable (P-values)

The outcome from univariate logistical regression revealed that with every year increase of age, the usage of low dose of aspirin was significantly decreased by 2% (odds ratios [OR]: 0.98, 95% confidence interval [CI]: 0.96–0.99). Female gender increased likelihood of low-dose use but as a nonsignificant trend (OR: 1.16, 95% CI: 0.75–1.78) [Table 3].

Table 3

Demographic variables

Patients with higher education attributed a significantly different effect as they were found to be more compliant as compared to people with no educational background. Marital status divulged no significant association with the use of different doses of aspirin (P = 0.922). Patients on low-dose aspirin had better rehabilitation as compared to patients on high-dose aspirin (P = 0.013) [Table 2]. Doctor counseling was nonsignificantly better for patients with a high-dose aspirin as compared to those taking low-dose aspirin (P = 0.265).

Results of multivariate logistic regression stipulated that all variables retained similar effect except for rehabilitation [Table 3]. It implied that when effect of age and qualification was adjusted, rehabilitation had no effect on usage of different aspirin doses (OR: 2.08, 95% CI: 0.75–5.73) [Table 3].

DISCUSSION

Long-term aspirin therapy confers conclusive net benefits on risk of subsequent MI, stroke, and vascular death among patients with a wide range of prior manifestations of cardiovascular disease. Because aspirin confers a risk of major bleeding, the appropriate dose is the lowest dose that is effective in preventing both MI and stroke as these two diseases frequently coexist.[10]

A 2003 analysis of data from the Clopidogrel in Unstable Angina to Prevent Recurrent Events trial demonstrated no significant difference in efficacy for low-dose aspirin (≤100 mg) versus high-dose aspirin (≥200 mg), but the researchers reported an increase in bleeding complications among high-dose aspirin users.[11]

The American Heart Association and the American College of Cardiology recommend that all individuals with existing cardiovascular disease take a low dose (75–100 mg) of aspirin daily for prevention of future cardiovascular events.[5]

In accordance with the current guideline, more than 70% of our population is taking low-dose aspirin as part of their regime. In addition, keeping with trends, the majority of such patients were married and males above 50 years of age.[1213] Men reach cardiovascular disease risk thresholds at an earlier age, which leads to a differential prescription pattern for aspirin treatment between genders based on age alone as a consideration.[14] The greater frequency of aspirin resistance found among women may be another factor in this disparity.[15] Hovens et al.[16] found that the prevalence of aspirin resistance was less among patients receiving >300 mg of aspirin per day (19%) compared to those receiving <100 mg of aspirin per day (36%). In keeping with the same, Gurbel et al. found that there is a dose-dependent inhibition of platelet function, as assessed by non-COX-1 pathways, which is why females are contemporarily recommended a higher dose of aspirin as compared to their male counterparts.[1718] Women are more likely to have a lower income than men, and lower-income individuals are more likely to go to non-evidence-based practices, so the trend of the underprescription of aspirin between genders may be explained by these factors.[101319]

Univariate logistic regression of our data shows that the probability of using high-dose aspirin increases by 2% with every year increase in age. This trend is not dissimilar to the ones observed in the United States[20] in spite of existing data that prove higher doses of aspirin post-MI produce an increased risk of side effects, the most important of which is gastrointestinal bleeding.[2122]

The secondary prevention with low-dose aspirin is widely recommended outside the U.S., with various national guidelines historically recommending daily doses of low-dose tablet.[12] This seems to be the case here – since from the 456 patients included in the study, 61% (273) had been prescribed low-dose aspirin along with some sort of prior counseling from their physician on the benefits of using the drug.

The term cardiac rehabilitation refers to coordinated, multifaceted interventions designed to optimize a cardiac patient's physical, psychological, and social functioning, in addition to stabilizing, slowing, or even reversing the progression of the underlying atherosclerotic processes, thereby reducing morbidity and mortality.[23] These practices are recommended as useful and effective (Class I) by the American Heart Association and the American College of Cardiology in the treatment of patients with CHD.

Our study showed that from among the 456 patients, only 9.6% had been given or had participated in rehabilitation therapy. The low numbers are not surprising, considering that this seems to be a universal third world problem with the percentages of MI patients going through rehabilitation therapy in Pakistan and India being comparable.[24] The authors believe that this is due to the low number of rehabilitation centers in the developing world with their being only 44 cardiac rehabilitation centers in Pakistan, of which 12 are located in Karachi.

From the low dose, i.e., more evidence-based treatment, aspirin group, 11.9% of patients underwent rehabilitation, while from the high-dose aspirin group, only 3.9% underwent some form of postoperative intervention.

Limitations

There are several limitations in our study that need to be considered. First, only patients from a single center were included in our study due to lack of feasibility and finances. Second, the hospital considered is a government-based hospital; hence, the majority of the sample belonged to low socio-economic background. Third, we did not account for all factors that may impact adherence to treatment regimens such as income and concomitant psychiatric illness. Finally, dosage of aspirin was based on patient self-report and medications shown and not on pill counts, electronic monitoring or refill data, which may be more reliable. To overcome these limitations, a large sample size was taken to minimize the effects of potential confounders.

CONCLUSION

Therefore, our study concludes that MI patients with higher education level and undergoing rehabilitative therapy are more likely to take low-dose aspirin as compared to those who failed to have these attributes. Further work is needed to confirm these findings and expand our recommendations, particularly the sensitive issue regarding adequate doctor counseling among these high-risk patients.

NGOs and governmental institutions can play a pivotal role in bringing out the true picture as defined in earlier studies and awareness projects. Further data regarding these patients should be collected on a national level, and appropriate measures should be taken both by the government and by the private sectors to reduce the mortality rate among these patients by educating the masses on the role of aspirin usage.

These focused efforts, if successful, would reduce the burden of related chronic heart disease in the country and region, as a whole, especially in such an area dominated with an elderly population.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.