Long-term use of secondary prevention medications for heart failure in Western Australia: a protocol for a population-based cohort study

Assuming one dose per day yields a similar estimate of medication adherence in patients with stroke: An exploratory analysis using linked registry data

PURPOSE

Prescribed daily dose (PDD), the number of doses prescribed to be taken per day, is used to calculate medication adherence using pharmacy claims data. PDD can be substituted by (i) one dose per day (1DD), (ii) an estimate based on the 75th percentile of days taken by patients to refill a script (PDD₇₅ ) or (iii) the World Health Organization's defined daily dose (DDD). We aimed to compare these approaches for estimating the duration covered by medications and whether this affects calculated 1-year adherence to antihypertensive medications post-stroke.

METHODS

We conducted a retrospective review of prospective cohort data from the ongoing Australian Stroke Clinical Registry linked with pharmacy claims data. Adherence was calculated as the proportion of days covered (PDC) for 1DD, PDD₇₅ and DDD. Differences were assessed using Wilcoxon rank-sum tests.

RESULTS

Among 12 628 eligible patients with stroke, 10 057 (80%) were prescribed antihypertensive medications in the year after hospital discharge (78.2% aged ≥65 years, 45.2% female). Overall, the 75th percentile of patient time until next medication refill was 39 days. The greatest variations in dose regimens, estimated using person- and dose-level refill times, were for beta blockers (11.4% taking two tablets/day). There were comparable levels of adherence between 1DD and the PDD₇₅ (median PDC 91.0% vs 91.2%; P = 0.70), but adherence was slightly higher using DDD (92.3%; both P < 0.001). However, this would represent a clinically nonsignificant difference.

CONCLUSION

Adherence to antihypertensive medications shows similar estimates across standard measures of dosage in patients during the first year after an acute stroke.

Long-Term Adherence to Renin-Angiotensin System Inhibitors and β-Blockers After Heart Failure Hospitalization in Senior Patients

AIMS

We investigated long-term adherence to renin-angiotensin system inhibitors (RASIs) and β-blockers, and associated predictors, in senior patients after hospitalization for heart failure (HF).

METHODS

A population-based data set identified 4488 patients who survived 60 days following their index hospitalization for HF in Western Australia from 2003 to 2008 with a 3-year follow-up. Their person-linked Pharmaceutical Benefits Scheme records identified medications dispensed during follow-up. Drug discontinuation was defined as the first break ≥90 days following the previous supply. Medication adherence was calculated using the proportion of days covered (PDC), with PDC ≥ 80% defined as being adherent. Multivariable logistic regression models were used to identify predictors of PDC < 80%.

RESULTS

In the cohort (57% male, mean age: 76.6 years), 77.4% were dispensed a RASI and 52.7% a β-blocker within 60 days postdischarge. Over the 3-year follow-up, 28% and 42% of patients discontinued RASI and β-blockers, respectively. Only 64.6% and 47.5% of RASI and β-blocker users, respectively, were adherent to their treatment over 3 years, with adherence decreasing over time (trend P < .0001 for RASI and trend P = .02 for β-blockers). Older age, increasing Charlson comorbidity score, chronic kidney disease, and chronic obstructive pulmonary disease were independent predictors of PDC < 80% for both drug groups.

CONCLUSION

Among seniors hospitalized for HF, discontinuation gaps were common for RASI and β-blockers postdischarge, and long-term adherence to these medications was suboptimal. Where appropriate, strategies to improve long-term medication adherence are indicated in HF patients, particularly in elderly patients with comorbidities.

Feature selection and transformation by machine learning reduce variable numbers and improve prediction for heart failure readmission or death

Background

The prediction of readmission or death after a hospital discharge for heart failure (HF) remains a major challenge. Modern healthcare systems, electronic health records, and machine learning (ML) techniques allow us to mine data to select the most significant variables (allowing for reduction in the number of variables) without compromising the performance of models used for prediction of readmission and death. Moreover, ML methods based on transformation of variables may potentially further improve the performance.

Objective

To use ML techniques to determine the most relevant and also transform variables for the prediction of 30-day readmission or death in HF patients.

Methods

We identified all Western Australian patients aged 65 years and above admitted for HF between 2003–2008 in linked administrative data. We evaluated variables associated with HF readmission or death using standard statistical and ML based selection techniques. We also tested the new variables produced by transformation of the original variables. We developed multi-layer perceptron prediction models and compared their predictive performance using metrics such as Area Under the receiver operating characteristic Curve (AUC), sensitivity and specificity.

Results

Following hospital discharge, the proportion of 30-day readmissions or death was 23.7% in our cohort of 10,757 HF patients. The prediction model developed by us using a smaller set of variables (n = 8) had comparable performance (AUC 0.62) to the traditional model (n = 47, AUC 0.62). Transformation of the original 47 variables further improved (p<0.001) the performance of the predictive model (AUC 0.66).

Conclusions

A small set of variables selected using ML matched the performance of the model that used the full set of 47 variables for predicting 30-day readmission or death in HF patients. Model performance can be further significantly improved by transforming the original variables using ML methods.

Comparison of Different Strategies to Measure Medication Adherence via Claims Data in Patients With Chronic Heart Failure

Medication adherence correlates with morbidity and mortality in patients with chronic heart failure (CHF), but is difficult to assess. We conducted a retrospective methodological cohort study in 3,808 CHF patients, calculating adherence as proportion of days covered (PDC) utilizing claims data from 2010 to 2015. We aimed to compare different parameters’ influence on the PDC of elderly CHF patients exemplifying a complex chronic disease. Investigated parameters were the assumed prescribed daily dose (PDD), stockpiling, and periods of hospital stay. Thereby, we investigated a new approach using the PDD assigned to different percentiles. The different dose assumptions had the biggest influence on the PDC, with variations from 41.9% to 83.7%. Stockpiling and hospital stays increased the values slightly. These results queries that a reliable PDC can be calculated with an assumed PDD. Hence, results based on an assumed PDD have to be interpreted carefully and should be presented with sensitivity analyses to show the PDC's possible range.

Evidence-based pharmacotherapies used in the postdischarge phase are associated with improved one-year survival in senior patients hospitalized with heart failure

AIM

Hospitalized heart failure (HF) patients have a poor prognosis postdischarge. We determined whether renin-angiotensin system inhibitors (RASI) and β-blockers dispensed to patients within 60 days post-HF hospital discharge are associated with improved 1-year survival.

METHODS

A retrospective population-based study was conducted in 4897 seniors, aged 65-84 years, alive at 60 days postindex HF hospitalization in Western Australia over 2003-2008. Dispensing of RASI and β-blocker dispensing was identified from the Pharmaceutical Benefits Scheme claims database linked to hospital admission and death records.

RESULTS

At 1-year posthospital discharge, the all-cause mortality and all-cause death or HF rehospitalization rate was 13.5% (n = 663) and 24.4% (n = 1193), respectively. Postdischarge RASI and β-blocker were dispensed in 77.4% and 53.0% of patients, respectively. Their use was associated with a lower inverse probability treatment weighted (IPTW) HR for 1-year mortality of 0.70, 95% CI 0.61-0.81 and 0.79, 95% CI 0.68-0.92, respectively (both P < 0.0001), with a survival advantage most evident in the subgroup (70.1%) of patients with ischemic HF. In the overall cohort, these therapies were also associated with reduced IPTW HRs for all-cause death or HF rehospitalization (both P < 0.005) but not for HF rehospitalization exclusively. Use of a β-blocker was associated with a reduced IPTW HR for HF rehospitalization in the ischemic HF subgroup only.

CONCLUSIONS

In a cohort of senior patients hospitalized with HF, dispensing of a RASI or β-blocker within 60 days postdischarge is associated with a 1-year survival benefit. Early postdischarge support programs after recent HF hospitalization should include measures to optimize adherence to evidence-based medications.