Peers as Facilitators of Medication Adherence Interventions

Abstract

Background: Difficulty taking essential medications as prescribed is a prevalent problem among people living with chronic diseases. Numerous interventions to enhance medication adherence have been developed; the majority facilitated by health care professionals. Objective: This review examined medication adherence interventions delivered by peers (ie, lay individuals living with the same chronic disease) and reports what is known about the impact of peer-facilitated interventions. Data Sources: PubMed, CINAHL, Google Scholar, Google, and PsychInfo, and ancestry searches. Study Selection: Solely peers delivered the intervention and follow-up occurred for at least 24 weeks postintervention. Electronic databases were searched from their start date to December 31, 2014. Results: Eleven studies were located that reported 10 different interventions focused on 6 chronic disease conditions. Most interventions were delivered in clinical settings and grounded in a theoretical framework. Formats were evenly split between individual and group level, with one intervention using both. Length of training for the interventionists and the number of intervention sessions that subjects received varied across studies. Limitations: Self-report was frequently used as a measure of adherence. Biomarkers were sometimes used to assess medication adherence; however, lifestyle modification may have also affected biomarker levels. Conclusions: Overall, the interventions had positive effects and attrition was quite low. Peer-facilitated interventions appear to enhance medication adherence as well as other healthful behaviors, such as exercise.

Introduction

Advances in medical science afford individuals who are living with a chronic disease the opportunity for enhanced health outcomes and a productive life by taking medications daily as prescribed.¹ However, for some people who are living with a chronic condition, taking medications on a daily basis for a lifetime can be a daunting task.² Nonadherence to medications as prescribed, sometimes termed noncompliance, is a prevalent problem and multifaceted phenomenon that can vary in nature between individuals, even within the same disease state.³ However, regardless of the specific disease, suboptimal medication adherence frequently results in negative health outcomes and increased morbidity and mortality.⁴ In selected chronic conditions, such as HIV disease, suboptimal adherence can become a threat to public health as nonadherence to HIV medications can result in an increased risk for transmitting HIV infection to other individuals.⁵ People with chronic diseases who are nonadherent to their medications often require more health care services, frequent hospital admissions, and complex treatment regimens.⁶ Addressing nonadherence in chronic disease is a significant challenge facing health care providers, policy makers, researchers, and the health care system in general.

Traditionally, professionals have been called upon to facilitate interventions that address individual and population health needs and problems. However, there is growing awareness that including patients, stakeholders, and community members in health care interventions can enhance effectiveness, particularly when addressing complex health conditions.⁷ There are published intervention models that have successfully used peers (ie, lay individuals) as facilitators to enhance health. Most studies using lay individuals to deliver intervention programs have targeted health promotion (eg, violence prevention) or an increase in screening uptake (eg, mammography).^8,9 Lay individuals have been successful as change agents in such endeavors. One successful example is the promotora model, which has been repeatedly used within the Latino population.¹⁰ A systemic review of obesity interventions for Latinos found strong evidence that promotora-led interventions are effective in reducing obesity.¹¹ The promotora model, also called the community health worker (CHW) model, is an effective strategy to enhance health outcomes.¹² The CHW model has primarily focused on educational interventions and some studies have included medication adherence as an outcome measure.¹³ However, promotoras and CHWs are not typically individuals who are living with the same disease as the target population.¹⁴

With regard to mediation adherence interventions, primarily it has been health care professionals, and not peers (ie, lay individuals living with the same disease), who have delivered such interventions.¹⁵ Despite concerted efforts and large numbers of medication adherence intervention trials, nonadherence to medications continues to be a vexing problem particularly among individuals with chronic disease conditions that require lifelong adherence to medications.¹⁶ The use of peers as facilitators of medication adherence interventions is a strategy that has promise and could enhance the cultural relevance of medication adherence interventions.¹⁷ In other words, lay individuals who are living with the chronic disease serve as facilitators of the intervention in an effort to enhance adherence among others who are also living with the same chronic disease.¹⁸

The current review was undertaken to explore the literature with regard to peer-facilitated medication adherence interventions and to examine what is known about the effectiveness of such interventions in chronic disease. In this article, published interventions that used solely peers (ie, individuals living with the same chronic disease as the target population) as facilitators and reported at least 6 months of follow-up on medication adherence are summarized. The review focuses on the characteristics of the interventions, interventionists, and the impact that peer-facilitated interventions had on adherence. Information is also presented about other health outcomes of interest to the studies included.

Methods

Data Sources

The original search of multiple databases was conducted January 2014 and updated January 2015. Selected electronic databases were searched from their start date through December 31, 2014 based on key terms, inclusion criteria, and exclusion criteria. The search engine Google was used to search for abstracts presented at conferences that might be of interest to this review. Ancestry searches were also conducted of the reference lists of publications that met the inclusion/exclusion criteria. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement guidelines were followed.¹⁹

Search Strategy and Study Selection

For this review, “intervention” was defined as a behavioral treatment that aimed to enhance the health behavior of medication adherence. To be included in this literature review, a peer-facilitated behavioral intervention had to have targeted a group of people living with a chronic disease who had been prescribed medications for said chronic disease by a physician, nurse practitioner, or physician’s assistant. Interventions that focused on enhancing medication adherence in diseases that require taking medications for a finite time frame were excluded. Reports of medication adherence interventions in chronic diseases that were facilitated by health care professionals or paraprofessionals were excluded, as were interventions that focused strictly on enhancing healthy behaviors in chronic disease that did not involve taking medications (eg, exercise, healthy eating) and hence did not include medication adherence as an outcome measure. To be included in this review, solely peers (ie, meaning lay individuals living with the same chronic disease) delivered the intervention. For example, interventions delivered by a lay individual in partnership with a professional or paraprofessional (ie, the lay individual and professional delivered the intervention together at the same time) were excluded. Also excluded were interventions where the peer was a proxy facilitator (ie, an educational video was shown to the participant of a peer speaking or a peer showed the participant an educational video of a nurse or physician speaking).

The following databases were utilized in this search: PubMed, CINAHL, Google Scholar, Google, and PsychInfo. The search strategy for PubMed was as follows: limits were set to include only articles published in English with no start date. The search end date was December 31, 2014. The key terms “medication,” “adherence,” and “intervention” were entered into the database search box together with the term “chronic disease.” Then these 3 key terms were entered again with each of the terms “diabetes,” “HIV,” “hypertension,” and “hyperlipidemia,” in place of “chronic disease.” The same searches were also conducted using the terms “lay” and “peer.” The initial searches yielded a total of 1163 articles. There were a number of articles that could be excluded simply by reading the title. The abstracts of 95 potentially relevant publications were then read and assessed for eligibility. If eligibility could not be determined by reading the abstract, the entire article was accessed and reviewed.

Data Extraction and Synthesis

One author independently abstracted each included study. The second author contributed to the interpretation of the extracted data. The following data were extracted: chronic disease targeted, author and year of publication, study design and period, country where study was implemented, type of setting where the study took place, intervention delivery format, theoretical framework, sample size, measure of adherence, other measures of interest to the study, characteristics of peer interventionists, training of peer interventionists, length of follow-up, attrition, study findings. Table 1 shows an overview of the studies included in the review by chronic disease targeted.

Table 1.

Overview of Studies by Chronic Disease Targeted.

Study and Location	Sample	Methods	Intervention	Impact
Dale et al (2009)22 United Kingdom, 40 general medical practices	N = 231 Gender: both Ethnicity: 90% white Disease: DM	Design: RCT, 3 arms Follow-up: 6 months % attrition peer arm: 6.7% Comparison arms: Usual care and nurse telephone support MA measure: Change in HbA1C Other measures: Self-reported self-efficacy for diabetes self-management	Peer Telephone Support: Format: Individual Dose: Minimum 6 calls over 6 months Tailored: Yes, frequency of calls changed based on participant’s needs Theoretical framework: Motivational interviewing Peer characteristics: 2/3 living with type 2 DM and 1/3 with type 1 DM Interventionist title: Peer supporter Training: 2 days Content: Empowerment, motivational interviewing, listening skills	No differences on HbA1C (P = .87) or self-efficacy (P = .68)
Heisler et al (2010)29 United States, 2 Michigan VA health care facilities	N = 244 Gender: Male veterans Ethnicity: 80% white Disease: DM	Design: RCT, 2 arms Follow-up: 6 months % attrition peer arm: 5% Comparison arm: Nurse case management MA measure: Change in HbA1C and self-report Other measures: BP, self-reported diabetes-specific stress, and diabetes social support	Reciprocal Peer Telephone Support Format: Individual, participants paired with peer by age Dose: Varied Tailored: Yes, ongoing weekly calls encouraged, 90% of pairs had at least one telephone conversation Theoretical framework: NR Peer characteristics: 56% on both oral medications and insulin Interventionist title: Peer partner Training length: 3-hour group session Training content: reviewed laboratory test results and BP results, basic communication skills	Peer arm better HbA1C (P = .004) Peer arm higher self-reported diabetes social support (P = .010) No differences on BP, self-reported MA, diabetes-specific stress
Chang et al (2010)27 Uganda 15 AIDS clinics	N = 1336 Gender: Both (66% female) Ethnicity: African Disease: HIV	Design: Cluster RCT 2:1 Follow-up: 96 weeks % attrition peer arm: 2% Comparison arm: Usual care MA measures: Pill counts and virologic failure (laboratory test) Other measures: CD4 cell count	Peer Health Workers (PHWs) Format: Individual Dose: Varied, typically biweekly peer visits, length NR Tailored: Yes, frequency and format changed based on participant’s needs (eg, home visit, worksite visit, mobile phone support) Theoretical framework: Pragmatically oriented Peer characteristics: Living with HIV, good adherence for at least 6 months and nominated by clinic staff Interventionist title: Community-based PHW Training length: 2 days Training content: HIV pathogenesis, medication information, adherence, counseling	Peer arm less HIV virologic failures at week 96 (P = .045) and at week 192 (P = .024) No differences on adherence per pill counts or on CD4 cell count
Pearson et al (2007)23 Mozambique, free HIV care clinic	N = 350 Gender: Both (54% female) Ethnicity: African Disease: HIV	Design: RCT, 2 arms Follow-up: 12 months % attrition peer arm: 3% Comparison arm: Usual care MA measure: Self-report Other measures: Chart abstracted CD4 cell count (laboratory test), self-reported stigma, self-efficacy, depression, and social support	Peer-delivered, modified directly observed therapy (peers also provided social support and information about the benefits and side effects of HIV medications as needed) Format: Individual Dose: 6 weeks Tailored: No Theoretical framework: IMB model Peer characteristics: Living with HIV, receiving care at study site Interventionist title: NR Interventionist title: Peer Training length: 1 week of training and a 1 day refresher every 3 months and weekly debriefing Training content: NR	Peer arm higher self-reported adherence (P < .05) No significant differences between arms on CD4 cell count, self-efficacy, depression, or social support
Simoni et al (2009)21,a United States, Seattle HIV clinic	N = 244 Gender: Both (75% male) Ethnicity: 47% white Disease: HIV	Design: RCT, 4 arms Follow-up: 9 months % attrition peer arm: 12% Comparison arms: Pager messaging, peer support + pager messaging, usual care MA measures: HIV viral load (laboratory test), MEMS, self-report Other measures: CD4 cell count	Peer support Format: Mixed format, peer support group and individual telephone calls from peer Dose: 3 months (6 twice monthly group sessions plus weekly telephone call) Tailored: No Theoretical framework: Social support Peer characteristics: Living with HIV, receiving care at study site, clinic staff reported as having high levels of adherence Interventionist title: Peer Training length: 15 hours Training content: Negative affective state assessment, barriers to adherence, provision of social support	Higher peer support (ie, higher attendance at peer group meetings) associated with reductions in HIV viral load (P = .01) Higher response to pager messaging (text messages) was associated with reduction in viral load (P = .01) and increases in CD4 cell count (P < .001) No differences on adherence per MEMS or self-report
Simoni et al (2007)20,a United States, New York HIV clinic	N = 136 Gender: Both Ethnicity: 46% African American, 44% Hispanic Disease: HIV	Design: RCT Follow-up: 6 months % attrition peer arm: 17% Comparison arm: Usual care MA adherence measures: HIV viral load, MEMS, self-report Other measures: Self-reported social support and depressive symptoms	Peer support Format: Mixed format, peer support group and individual telephone calls from peer Dose: 3 months (6 twice monthly group sessions plus weekly telephone call) Tailored: no Theoretical framework: Social support Peer characteristics: Living with HIV, receiving care at study site, clinic staff reported as having high levels of adherence Interventionist Title: Peer Training length: 16 hours over 4 days Training content: Negative affective state assessment, barriers to adherence, provision of social support	No differences on % overall adherence per MEMS No differences on HIV viral load Peer arm higher 3-day self-reported adherence (P < .05) and social support (P < .05) and decreased depressive symptoms (P < .05)
Zuyderduin et al (2008)24 Botswana, Coping Centre for People with AIDS	N = 77 Gender: Females Ethnicity: African Disease: HIV	Design: Quasi-experimental2 arms Follow-up: 6 months % attrition peer arm: 0% Comparison arm: Usual care MA measure: Self-report Other measures: Self-reported disclosure of HIV status, CD4 cell count checks, taking TB prophylaxis	Buddy system Format: Individual Dose: 6 months Tailored: Yes, buddy to spend 4 to 6 hours a week with study participant but could be more Theoretical framework: Orem’s Self-care theory Peer characteristics: Woman living with HIV, typically more open about HIV status Interventionist title: Buddy Training length: NR Training content: Basic HIV/AIDS knowledge, compliance with TB treatment, CD4 cell counts, adherence and support skills	Peer arm higher self-reported adherence (P = .049) and HIV status disclosure (P = .009) No differences on having CD4 cell count checks and taking TB prophylaxis
Truncali et al (2010)28 United States, New York City Senior Centers	N = 105 Gender: Both Ethnicity: NR Disease: HTN	Design: Pre/post (no control group) Follow-up: 6 months % attrition: 0% Comparison arm: NA MA adherence measure: Change in systolic BP Other measures: None	Keep On Track (KOT): Educational messaging and monitoring of bp by a peer counselor Format: Individual Dose: Varied Tailored: Yes, participant came to senior center to meet with peer as desired Theoretical framework: NR Peer characteristics: Community-dwelling older adults living with HTN, routinely attended senior centers Interventionist title: Peer counselor Training length: Six 2-hour sessions, 75-page training manual Training content: How to use a BP cuff, effective communication, observation, and hands-on practice	Overall decrease in systolic BP (P = .04) Participants with baseline systolic BP >160 mm Hg had mean decrease of 20.9 mm Hg (P < .001)
Coull et al (2004)25 Scotland, hospital	N = 319 Gender: Both Ethnicity: NR Disease: Ischemic heart disease	Design: RCT, 2 arms Follow-up: 12 months % attrition peer arm: 10% Comparison arm: Usual care MA measure: Self-report Other measures: Self-reported exercise activity and dietary intake	Braveheart: Lay health mentoring Format: Group Dose: Twelve 2-hour peer-led group sessions, held monthly over 1 year Tailored: No Theoretical framework: Rogers’ person-centered approach Peer characteristics: Age 54-74 years, Community-dwelling Interventionist title: Health mentor Training length: 30 hours with ongoing support from project coordinator Training content: Self-help principles and group facilitation using person-centered approach	Peer arm higher self-reported adherence (P < .01) Peer arm exercised more and had better dietary behaviors (P < .05)
Rothrock et al (2006)30 United States, university-based clinic	N = 100 Gender: Both (92% female) Ethnicity: NR Disease: Migraine headache	Design: RCT Follow-up: 6 months % attrition peer arm: 0% Comparison arm: Usual care MA adherence measure: Self-report via diary entries Other measures: MIDAS scale (Migraine Disability Assessment Score)	Headache school Format: Group classes held evenings and weekends Dose: Three 90-minute sessions Tailored: No Theoretical framework: NR Peer characteristics: Adults living with migraine headaches Interventionist title: Lay migraineurs Training length: 12 hours classroom training plus 12 hours observation Training content: NR; however, stated that training was intense	Peer arm higher adherence, 96% vs 58%, per medication diary entries (P = NR) Peer arm lower MIDAS score (P < .05) Peer arm less headache frequency (less days per month with headache) (P = NR)
Druss et al (2010)26 United States, community mental health clinic	N = 80 Gender: Both (80% female) Ethnicity: 83% African American Disease: Serious mental illness	Design: RCT Follow-up: 6 months % Attrition peer arm: 10% Comparison arm: Usual care MA adherence measure: Self-report Other measures: Patient activation (perceived ability to manage ones illness and health behaviors); Physical Activity and Physical Health Quality of Life; Mental Health Quality of Life	HARP (Health and Recovery Peer Medical Self-Management) Format: Group Dose: 6 sessions Tailored: No Theoretical framework: Lorig’s (1999) chronic disease self-management model Peer characteristics: Persons living with serious mental illness Interventionist title: Peer specialist Training length: 5-day training on Lorig’s (1999) chronic disease self-management program plus 3 days training with PI Training content: Lorig’s training program was tailored for persons with serious mental illness	Peer arm higher self-reported adherence (P = .22) Peer arm higher patient activation (p = .03) Peer arm higher physical activity and physical health related quality of life (P = .41) No difference on mental health quality of life

Abbreviations: AIDS, acquired immunodeficiency syndrome; BP, blood pressure; CI, confidence interval; DM, diabetes mellitus; HbA1C, hemoglobin A1C (glycated hemoglobin); HIV, human immunodeficiency virus; HTN, hypertension; IMB model, informational, motivation, and behavioral skills model; MA, medication adherence; MEMS, medication event monitoring system (ie, electronic drug monitors); NA, not applicable; NR, not reported; TB, tuberculosis; VA, Veterans Affairs.

^aBoth studies tested same intervention.

Results

Eleven articles met the inclusion criteria for this review (see Figure 1). These articles reported findings about 10 different peer-facilitated interventions, which included medication adherence as an outcome measure. All interventions targeted adults and no published peer-facilitated interventions were located that targeted children. One of the interventions was tested twice and published as 2 separate studies.^20,21 There were 6 different chronic diseases targeted by the interventions, with HIV being the most common. Most of the studies employed a randomized controlled design, were conducted in the United States, and used medical settings as their recruitment sites. The number of participants in each study ranged from 77 to 1336. The majority of studies used some type of theoretical framework and a variety of formats were used to deliver the peer-facilitated interventions. Length of follow-up ranged from 24 to 96 weeks and overall attrition was low.

Figure 1.

Literature review flow diagram.

Theoretical Frameworks

Most of the studies reported the use of some type of theoretical framework to guide the intervention. Two studies did not report on theory utilization but overall there was emphasis on communication and social support, although a specific communication theory or social support theory was not cited. Theories and frameworks used to guide the peer-facilitated interventions included motivational interviewing,²² social support,^20,21 IMB (informational, motivation, and behavioral skills) model,²³ Orem’s self-care theory,²⁴ Rodgers’ person-centered approach,²⁵ and Lorig’s chronic disease self-management program.²⁶ Except for the 2 studies that examined the same intervention grounded in social support theory, no other studies utilized the same theoretical underpinnings.

Intervention Format and Length

The format and length of the peer-facilitated interventions differed. Six interventions used an individual level approach: 4 were delivered in a face-to-face format^23,24,27,28 and 2 were delivered via telephone.^22,29 While most interventions were delivered at the individual level, there were 3 studies that used a group format^25,26,30 and 1 that used a mix of a support group together with individual telephone contact.^20,21 One of the group interventions used a peer mentoring strategy²⁶ and the other two used a group format to provide education. Some interventions could be delivered as often as daily,^22-24 others weekly,^{20,21,26,27,29} and still others were delivered monthly.²⁵ The duration of the interventions ranged from 6 weeks to 6 months.

The frequency and duration of the interventions varied greatly. Some interventions tailored the number of intervention sessions and contacts with the peer based on the needs of the participant.^{22,24,26,28,29} For example, the location of contact with the peer facilitator (eg, home visit vs work site vs phone support) was based on participant preference, as was the frequency of contact. Other interventions had a set number of sessions, which ranged from 3 to 12, but varied in the length of delivery. For example, some interventions sessions were held weekly, while others were held biweekly or monthly.

Populations and Diseases Targeted

All studies targeted adults living with a chronic condition. The most common condition was HIV with five studies, albeit only 4 different interventions.^{20,21,23,24,27} Three of the HIV studies were conducted in African countries in community-based settings and clinics.^23,24,27 The other 2 HIV studies occurred in large East and West coast HIV clinics located in the United States and tested the same intervention.^20,21

There were 2 studies focused on adults with diabetes: one study targeted individuals who were taking oral medications²² while the other included individuals who were taking oral and/or injectable medications or both.²⁹ The 2 diabetes studies were both conducted in medical settings. One diabetes study was conducted in medical practice settings across the United Kingdom,²² while the other was conducted in 2 US Veterans Administration settings in the same state.²⁹

The remaining 4 studies targeted adults with hypertension,²⁸ ischemic heart disease,²⁵ migraine headache,³⁰ and serious mental illness.²⁶ The ischemic heart disease study was conducted in Scotland and the others in the United States. The study targeting individuals with hypertension was conducted in a community setting and the other 3 studies were set in medical centers.

Characteristics and Training of Interventionists

All interventionists were lay individuals (ie, not health care professionals) who were living with the same chronic condition as the target population. The title given to the peer interventionists varied among the studies. Titles given to interventionists included such names as lay facilitators, buddies, partners, lay health mentors, and supporters, while some studies simply called them peers.

All interventions provided some form of structured training to the peer interventionists. Training ranged from as little as one 3-hour group session prior to beginning the intervention, to 30 hours of training followed by ongoing in-services throughout the course of the study. One study reported that some peers had to be dismissed from the study during training due to an inability to master the intervention technique (ie, motivational interviewing).²² Another study reported a requirement that peer facilitators show competency by passing a written test at the end of the training.³⁰

Medication Adherence Outcomes

For the most part, adherence was measured using self-report via oral interview or written questionnaires. Several studies used biomarkers or vital signs as a proxy measures of adherence (ie, HbA1C, blood pressure, HIV viral load, CD4 cell count).^20-23,27-29 One study used pill counts to measure adherence²⁷ and 2 studies used medication event monitoring systems^20,21 (ie, electronic monitoring caps on pill bottles): these were all HIV studies. Furthermore, there were studies that used a combination of measures to examine adherence (eg, self-reported medication adherence and change in HbA1C).

Other Outcomes

In addition to adherence, a variety of other outcome variables were also examined by several studies.^{20,22-26,29,30} Like adherence, the majority of the other outcome variables were also measured using self-report. Other variables of interest included stress,²⁹ social support,^20,23 self-efficacy,^22,23 depression,^20,23 exercise/physical activity,^25,26 and quality of life.^26,30

Attrition and Attendance at Intervention Sessions

Overall attrition (ie, dropout) rates were low and attendance at intervention sessions was high across the studies reviewed, but particularly so for the peer arms. Because several of the studies targeted populations with serious life-threatening conditions (ie, AIDS, ischemic heart disease), death was treated as a study end point, rather than attrition. There were 3 studies with 0 attrition,^24,28,30 with the majority of the studies experiencing attrition rates between 2% and 10% in the peer-delivered intervention arms.^{22,23,25-27,29} Just 2 studies had attrition rates more than 10% in the peer groups: one study had 12% attrition²¹ and the other had 17%.²⁰ Attrition rates in the comparison/control arms were somewhat higher and ranged from 4% to 28%. The studies with the lowest attrition also had the highest intervention attendance rates. In other words, participants attended more sessions and therefore had more contact time with peers over the course of the intervention. The highest rates of attrition, and also the lowest attendance at intervention sessions, were seen in US studies that targeted individuals with HIV/AIDS.

Intervention Impact

Ten of the 11 studies in this review reported positive findings among participants in the peer arm. Eight of the 10 studies with positive findings had statistically significant increases on medication adherence in the peer-facilitated intervention arm. The 2 interventions that did not report significant improvement with regard to medication adherence did however report other significant findings. One of these interventions was focused on enhancing patient activation, which did increase significantly (P = .03), while medication adherence was considered a secondary outcome.²⁶ The other study focused on reducing migraine disability as its main outcome, which decreased significantly.³⁰ Of note, the migraine intervention study reported that participants in the peer intervention arm experienced a 38% higher adherence rate to their prophylactic medication to prevent headache. The increased adherence in the use of prophylactic medication was considered to be clinically significant for this particular disease condition.³⁰

The interventions that enhanced adherence, also positively affected other variables of interest to the studies reviewed. Two studies reported significant increases on social support among participants who received the peer-facilitated interventions.^20,29 Two other studies reported significant increases in exercise/physical activity in the peer arms.^25,26 Finally, several studies reported significantly better emotional health/quality of life outcomes in the peer arms.^20,24,26,30

All of the interventions with very low attrition (0 to 3%) reported significantly increased medication adherence in the peer arm. The lowest attrition interventions were all tailored in some fashion. Strategies to tailor the interventions involved adapting the dose, place of delivery, and/or content of the intervention based on the needs of the participants.^23,24,27,30 Most of the interventions with very low attrition rates were delivered at the individual level; however, one was a group-level intervention.³⁰ Interventions with low attrition rates also had more frequent peer contact over longer periods of time.

The highest impact on medication adherence measures was reported for interventions that were delivered face-to-face. There was a mixed format intervention that consisted of face-to-face, telephone, and/or text messaging, which reported that the greatest impact on the main clinical outcome measure of adherence occurred among the participants who had the highest amount of face-to-face contact time with peers.²¹ The 2 peer interventions delivered solely by telephone were not found to be as effective as the face-to-face peer-facilitated interventions.^22,29 Both telephone interventions addressed diabetes mellitus and used HbA1C as a proxy measure of adherence. One telephone intervention study had null findings.²² The other telephone intervention had no impact on self-reported medication adherence but participants in the peer arm did have significant improvement on HbA1C.²⁹

Discussion

This review explored what is known about peer-facilitated mediation adherence interventions in chronic disease. For this review, peer-facilitated meant that the intervention was led by a lay individual living with the same chronic disease as the target population. Despite setting no limit on search start dates, only 11 studies were located that solely used peers to deliver behavioral medication adherence interventions to individuals living with chronic diseases. These 11 studies reported on 10 different interventions; one of the interventions was published twice as it was tested in 2 separate randomized clinical trials.

Medication adherence and other important clinical outcomes changed significantly in the desired direction across the peer-facilitated interventions reviewed here. Overall, attrition was low, particularly in the peer-delivered intervention arms of the studies. By comparison, a recent meta-analysis of health care provider led medication adherence interventions found a modest rate of attrition (22%).³¹ Thus, having a peer as the intervention facilitator may have helped decrease attrition. The strategy of using peers as intervention team members may warrant further investigation with regard to retention.

The majority of interventions had some type of theoretical underpinning. The most effective interventions were those delivered in a face-to-face format where participants had more contact with peers for a longer period of time. These interventions also had the highest engagement with regard to intervention attendance and the lowest attrition rates. Face-to-face interventions delivered over long time periods have also been shown to be effective when delivered by health care providers.³¹ However, peers may be a more cost-effective strategy for delivering long-term and time-consuming medication adherence interventions.

Despite the encouraging findings of this review, some methodological issues must be considered when interpreting the results. The measure of adherence used may have been a limitation for some studies. Self-report, which can be overestimated, as the single measure of adherence was common among the studies included in this review. Historically the use of self-report has been a predominant measure of adherence in medication adherence intervention studies for a variety of reasons.^31,32 In this review, many authors cited limited resources as their rationale for using self-report as the measure of adherence, instead of other more resource intense measurements such as medication event monitoring system.

Long-term follow-up of adherence postintervention was limited. Although this review required that participants have at least 6-months of follow-up, there was only one study located that was excluded from the review because the follow-up was too short. In fact, most studies that met the inclusion criteria for this review had only 6-month follow-up, with just 3 studies followed participants for a longer period of time. Hence, longer follow-up may need to be considered in future studies.

This review had other limitations, which must be considered when interpreting the results. Despite its systematic format, it is possible that articles reporting peer-facilitated medication adherence interventions could have been missed because peer-facilitated interventions are not well indexed in computerized databases. Because this review was limited to English language, peer-facilitated interventions conducted in other countries and published in other languages were excluded. In addition, some intervention characteristics may not have been reported and therefore could not be included in this review. Limited reporting of information about the interventions themselves precludes implementation in practice or efficient further research. For example, there were a handful of community health worker-led interventions in the published literature that examined medication adherence but did not describe the interventionists, except to state they were lay individuals. In those cases, it was not possible to determine if the community health workers were, or were not, living with the same chronic disease as the target population. Hence, those articles were excluded and may indeed have had promise but could not be assessed for the ability to enhance and sustain adherence.

Finally, there are lifestyle-related behavior modifications that must also be considered when interpreting the results of this review. For the studies that used biomarkers or vital signs as proxy measures of adherence, one must consider that in some chronic conditions lifestyle behaviors can significantly affect outcomes. For example, the biomarker HbA1C, which was used as a proxy measure of adherence to diabetes medications in some of the studies included in this review, is impacted by lifestyle modification. Hence, one must acknowledge that lifestyle modification behaviors, and not just medication adherence, may have affected this laboratory test which measures average plasma glucose concentrations. For example, behaviors like participating in exercise and eating a reduced calorie diet can play a significant role in the glucose levels of a person who is living with diabetes.³³ Therefore because the outcome measure of HbA1C is dependent on multiple factors, medication adherence alone may not have been the only factor that impacted the direction of this biomarker.

Albeit some limitations, the peer-facilitated interventions presented in this review had positive findings overall. Participants appeared to be highly engaged in the majority of the interventions. Peer-facilitated interventions had positive effects on medication adherence and other desired behaviors such as exercise, which suggest that this strategy has promise. Hence, interacting with a peer who is experiencing the same health problem may help the person with a chronic disease to engage in healthful behaviors.

A limited number of peer-facilitated medication adherence intervention studies were located by this review. The eleven studies that were identified were all published fairly recently, between 2004 and 2010. Given the vast amount of published literature addressing medication adherence, the small number of 11 suggests that the utilization of peers as facilitators of medication adherence interventions is in the beginning stages. Another plausible explanation may be that barriers exist to the use of peers as medication adherence facilitators; hence relatively few such studies have reached fruition. More research to examine the impact of peers as facilitators of medication adherence in clinical and community settings, together with an exploration of possible barriers to the utilization of peers as intervention facilitators, seems warranted.

Author Biographies

Maithe Enriquez is associate professor at the University of Missouri Sinclair School of Nursing. Her NIH funded research uses community-partnered interventions to enhance medication adherence and her clinical practice focuses on vulnerable adults living with chronic diseases.

Vicki S. Conn is Potter-Brinton Distinguished professor at the University of Missouri Sinclair School of Nursing. Her NIH funded research uses meta-analysis to examine physical activity behavior change and medication adherence interventions.