Background

Russia has one of the highest mortality rates from circulatory diseases in the world. In 2015 the age-standardized death rate was 368.8 per 100.000 [1], 2.5–4 times higher than in West European countries [1]. Arterial hypertension (HT) is among the main risk factors [2], affecting an estimated 44% of the Russian adult population [3], with only 53% of those with HT being controlled [3].

One reason for poor blood pressure (BP) control is thought to be inadequate adherence to treatment, [4] a substantial problem everywhere. A review of 21 clinical studies conducted outside Russia found that adherence to antihypertensive therapy (AHT) falls with time from diagnosis, with about half of patients discontinuing treatment after one year [5]. This poor adherence is, as expected, associated with treatment failure and adverse cardiovascular events [6] while good adherence has been linked to fewer adverse cardiovascular outcomes [7].

The scale of the problem means that much research has been undertaken to identify factors associated with poor adherence and to develop measures to improve it. However, while some of the conclusions from this work are generalizable across countries, it is important to take account of context, as there may be differences in health beliefs (such as understanding of the importance of continuing treatment indefinitely for an asymptomatic condition), health systems (such as how medicines are paid for, and other circumstances). Moreover, context-specific evidence is more likely to be accepted by national policy makers.

Here we report a scoping review of all Russian language studies presented in full-text reports on the problem of adherence to antihypertensive medication in the Russian population, the factors associated with adherence, interventions to improve adherence to treatment, and their effectiveness. This makes two distinct contributions. First, it provides the most detailed and comprehensive overview of what is known from the published literature about this important issue in Russia, summarizing the often neglected corpus of work published in the Russian language. Second, we have summarized the results of research in the quantitative indicators and described of the revealed patterns.

As many readers will be unfamiliar with the Russian health system, we summarize the key elements of medicines supplies in Table 1.

Table 1 Pharmaceuticals in the Russian health system
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Research questions

We address the following questions by means of a scoping review of the Russian language literature pertaining to studies of adherence to antihypertensive medications conducted in Russia:

  1. 1.

    What levels of adherence are found among adults diagnosed as hypertensive?

  2. 2.

    What sociodemographic and clinical factors are associated with adherence?

  3. 3.

    What robust evidence has been generated as to effective interventions used in Russia to increase adherence to treatment?

Methods

This scoping review was reported in accordance with the reporting guidance provided in the Preferred Reporting Items for Systematic reviews and Meta-Analyses statement extension for Scoping Reviews (PRISMA-ScR) [10] (Additional file 1).

ScR protocol was not published.

Eligibility criteria

Reports were included in this scoping review if they met the following criteria:

  • Target population included the Russian adult population aged 18 years and over with a diagnosis of HT defined as BP ≥140/90 mmHg and/or taking regular antihypertensive medication;

  • Articles that report on adherence to AHT, regardless of how adherence is measured;

  • Types of study designs - randomized controlled trial studies, non-randomized trial studies, observational studies (cross-sectional, cohort studies), registers;

  • Reports published in the Russian language;

  • Full-text original reports;

  • Published in journals or proceedings of conferences;

  • Literature published from January 2000 to November 2017. The last search was conducted in November 28, 2017.

There was no restriction on duration of treatment or sample size. There were no restrictions on interventions, comparators, and outcomes.

Information sources

Searches of the main Russian and international electronic databases were complemented by iterative searches using Internet search engines, personal contact with Russian experts working on HT, and queries to authors of identified studies by phone or e-mail (also used where clarification was sought about survey methods, instruments (such as the name of the questionnaire) and duration of observation). Reference lists were also searched. This comprehensive approach was taken to reduce potential bias by including only easy-to-locate studies that may have larger effect sizes due to publication bias.

The Russian databases were:

The international databases were:

The search for sources was conducted between October 2017 and November 2017 (last date searched).

For eLIBRARY.ru 333 publications were obtained by October 17, 2017.

For Russian Medicine 69 publications were obtained by October 20, 2017.

For Embase 87 publications were obtained by November 10, 2017.

For MEDLINE (PubMed) 31 publications were obtained by November 28, 2017.

The personal contacts with authors to identify additional sources were conducted from December 2017 to January 2018.

If more than one publication related to the same study, all were used to provide as much information as possible.

Full search strategies specific to the different databases are provided in Additional file 2.

Study selection

Having eliminated duplicates, titles and abstracts were reviewed by 2 researchers to assess eligibility, with differences resolved by discussion or, where necessary, by consultation with a third team member. Those not available electronically were obtained as hard copies. Those potentially eligible were read by each researcher to confirm eligibility and those retained were categorized to covering one or both of the following two areas:

  1. a)

    Levels, patterns and determinants of adherence

  2. b)

    Interventions to improve adherence, including evaluations of effectiveness

Each paper was read three times by a different team member who extracted the key findings.

Data charting process

Authors created a matrix (an Excel spreadsheet) to chart relevant information about all the sources reviewed. Specifically, the chart included details about the authors, year of publication, study setting, population/participant selection criteria, study design, sample size, age of participants, HT grade, nature of intervention, adherence measure, factor associated with adherence and main results (Table 2, Additional files 3, 4 and 5). Matrix was piloted with five papers and adapted in the light of this experience.

Table 2 Characteristics of included studies on adherence to antihypertensive therapy in adult population in Russia from 2000 to 2017
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Data items

A range of variables were extracted from reports of the studies.

Article details such as title, first author, date of publication, year of distribution, publication status, region(s) in which the study was conducted, and institutional setting.

Study design: randomized or non-randomized trial, cohort study, case-control study, register-based. If the design was a trial, we collected additional information on allocation concealment. Study objective, study duration, and sample sizes were also extracted.

Definitions of adherence: type of adherence measure: 4-item Morisky Medication Adherence Scale (MMAS-4), pill counts, bespoke questionnaire, etc.; indicators of adherence: MMAS-4 score points, percentage achieving a score of 4, pill counts compliance, and percentage of adherent people etc. (Additional file 3).

Determinants of adherence were extracted. These included baseline sociodemographic characteristics of HT patients: sex, age, education level, marital status, employment status, income, living in a city; disability; clinical characteristics of patients: HT grade, duration of HT, physical activity; associated clinical conditions (for example, ischemic heart disease, history of myocardial infarction, hypertensive crisis, etc.); concomitant diseases (for example, diabetes mellitus, panic attacks, subclinical depression, etc.); other data on instruments used in surveys; pharmacological therapy: therapeutic category, INN and commercial name, drug administration schedule, dose, dosage form; eligibility for the Medicine Assistance Scheme (MAS) which provides free drugs for certain categories of patients; home BP device availability; and frequency visits to the doctor (Additional file 4).

Intervention characteristics

Examples of content extracted included specific strategies to address barriers to adherence: special packaging of medications (e.g. blister packs, pill boxes), amount of prescribed medications, eligibility for the MAS, interventions designed to improve communication with patients, including more frequent visits, motivational interviewing, patient education, home BP monitoring, and provision of written instructions etc. (Additional file 5); mode of delivery: face-to-face, telephone, internet etc.; professions involved: pharmacist, physician, etc.; duration and number of sessions/consultations; and any other types of interventions in the experimental group;

Other data recorded included the main results, BP dynamics, achievement of target BP levels, author’s conclusions, and any reason for excluding the article.

Study quality assessment

In assessing the quality of study, we considered use of validated questionnaires, objective methods for adherence assessing, study design, presence of randomization, blinding, sample size, and follow-up as appropriate.

Synthesis of results

We grouped the studies by study questions analyzed (adherence, determinants and interventions), and summarized the type of settings, populations and study designs for each question, along with the measures used and a summary of findings. The results of this scoping review were synthesized using both a numerical summary, outlining relevant data from the included studies, and a narrative synthesis interpreting the results.

Results

The initial search identified 520 references (Fig. 1). Of these 120 were excluded because it was not possible to obtain the abstract despite exhaustive searches. Most of these were published in regional journals unavailable in electronic format, with only tables of contents available online, printed in individual regions in small numbers.

Fig. 1
figure 1

Flow diagram indicating the study selection process on adherence to antihypertensive therapy in adult population in Russia from 2000 to 2017

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The remaining 400 were screened against the inclusion criteria. The 235 potentially relevant reports were reviewed as full texts (eight were not available electronically, but three could be obtained as hard copies, leaving 5, from local journals that could not be obtained), leaving 31 eligible reports included in the review. The results from 2 studies were presented in 2 separate publications, resulting in us considering data from 29 individual studies.

The characteristics of the studies are presented in Table 2. Overall we included seven randomized intervention studies, ten cross-sectional studies, eleven prospective observational intervention studies (including six multicenter studies), and one report based on data from a register. None of the randomized studies were blinded. In four of the prospective observational intervention studies, it was only possible to extract baseline data as follow up data were not reported [24, 28, 30, 34]. Results from these studies were transformed into cross-sectional data.

The total number of patients in the studies selected for analysis was 23,127, with individual studies size ranging from 30 to 4816 participants.

The duration of follow-up varied from 6 weeks to 48 months.

Adherence measurement

Adherence to AHT was assessed using MMAS-4 in 18 of the 29 studies. Ten studies used a bespoke questionnaire or a single question about regularity of taking drugs that was included in a questionnaire on a wider range of issues, supplemented with 3 clarifying questions. The bespoke instruments included pill counts in 6 studies; the MMAS-4 but analyzed in a non-standard way in 1 study [34], and the Morisky-Green questionnaire, modified with 2 additional questions in one study [35]. Several studies used more than one method, for example MMAS-4 and pill counts.

No studies used objective methods of assessing adherence - measurement of drugs in biological fluids in blood, urine, or indirect methods - electronic dispensers. The bespoke questionnaires were only available in Russian and there was no information about whether they had been validated.

Adherence was assessed using data from cross-sectional surveys and from baseline data in prospective observational intervention studies. In studies using the MMAS-4 [11,12,13,14,15,16,17,18,19, 21, 23,24,25,26,27, 30, 33] adherence to AHT varied from 1.62 ± 0.27 [11] to 3.12 ± 0.86 points [35] out of a maximum of four (Additional file 3). Among these studies, the highest rates of adherence were found in post-marketing studies, all with large sample sizes. Scores were 2.8 [19], 2.78 [16], 2.95 [18] and 3.12 ± 0.86 points [35]. In the studies reporting baseline adherence, the highest rates were in those that included a high proportion of patients with concomitant diseases: ischemic heart disease, chronic kidney disease, stroke, transient ischemic attack, diabetes mellitus, etc. [29], who can be expected to have a strong motivation to adhere to medication. The lowest baseline adherence rates, with scores of 1.62 [11] and 1.7 [31] were observed in studies with a small number of patients who only had HT.

Eleven studies measured the proportion of “adherent” patients, i.e. reporting 4 points on the MMAS-4. Results varied, from 11.1% [15] to 44.2% [35]. The highest proportion of “adherent” patients was again noted in a study where many subjects had concomitant diseases [35].

Adherence, as measured by bespoke questionnaires was reported in eight out of nine papers [20, 22, 28, 29, 37,38,39,40,41], one of the studies being published in two papers [38, 39], three studies reporting baseline adherence [20, 22, 37]. In two studies, 38.5 and 74.9% of patients took AHT daily [22, 38], in another 56% fully complied with medical recommendations, including the use of antihypertensive drugs [28], “high adherent”, “sufficiently adherent” or “regularly taken” according to the criteria set by the researchers varied from 23.3 to 60.5% [20, 29, 37, 40, 41]. However, these findings are difficult to compare with those from other studies because of lack of information on the instruments used.

Adherence using pill counts was examined in five studies [31,32,33,34, 36] but baseline adherence rates were reported in only 3, ranging from 5 [31] to 43% [32]. This large difference may reflect the small sample sized (60 and 115).

Factors associated with adherence to antihypertensive therapy

12 studies examined associations between adherence and various socio-demographic, clinical and other variables (access to the MAS, home BP monitoring, frequency of visits to a doctor, etc.). Higher adherence was associated with female gender [29, 33, 35, 38, 41], age over 50 years [29, 33], not living alone [29, 38], employment [27, 33], higher education [33], and living in a city [41] (Additional file 4).

Higher adherence was associated with comorbidity, including: ischemic heart disease [24, 29, 38], history of myocardial infarction [26, 29], arrhythmias [27], diabetes mellitus [24, 29, 35], and psychiatric disorders [27]. High adherence was also associated with onset of HT at a young age [27] and use of fixed dose combination therapy [38].

The findings of studies of the association between adherence and grade of HT, experience of hypertensive crisis, and duration of HT were not consistent [27, 29, 33, 38,39,40,41].

There was no evidence that adherence was associated with income and physical activity [29].

Features of patient management in outpatient settings and adherence to therapy

Home BP monitoring [24, 29, 31] and more frequent visits to the doctor [34] were associated with better adherence. The association with eligibility for the MAS was also conflicting. In two studies [24, 39] it was associated with lower adherence [24] or failure to follow the recommended regimen [39] but in another, there was no association [38].

Taking multiple antihypertensive drugs (2 or more) was associated with decreased adherence [35, 39].

Assessment the effectiveness of interventions aimed at increasing adherence

Interventions to increase adherence were mainly either patient education (in various forms) in 6 studies [12, 13, 19,20,21,22,23] or optimization of the drug administration regimen in 11 studies [11,12,13, 15,16,17,18,19, 32, 33, 35, 36], among which 9 used a fixed-dose combination of drugs [11, 15, 16, 18, 19, 32, 33, 35, 36]. One study gave patients an electronic version of the SCORE scale, with the physician showing the patient how their risk would be reduced if they stopped smoking, controlled their BP and reduced their cholesterol [14]. In two studies [31, 37] patients were trained in home BP monitoring, intended to increase adherence.

Several studies used more than one method to increase adherence.

Randomized controlled intervention studies

In one study [12], a multi-faceted intervention, which included information within an educational program for patients, a free first package of antihypertensive drugs, regular visits to the doctor, and telephone reminders, was associated with a significant improvement in adherence. After 12 months, the proportion of adherent patients who achieved an MMAS-4 of 4 points in the intervention group was 71.7%, up from 52.2%, in the control group. The difference at follow up was highly significant (p < 0.0001) (Additional file 5). Demonstration of an electronic version of the SCORE scale to patients, highlighting benefits of reducing cardiovascular risk by smoking cessation, BP control, and reduced cholesterol, was associated with higher adherence than in a control group, with scores at 6 months of 2.75 and 1.88 points (p < 0.001), respectively, and 2.14 and 1.27 points (p < 0.001), respectively after 12 months [14].

Training patients in home BP monitoring was associated with significant improvement in adherence, with the effect persisting at 1 year [37].

Provision of an automatic BP monitor was associated with a significant increase in adherence to AHT, with a MMAS-4 score increasing from 1.7 ± 1.2 to 3.0 ± 1.1 points, p < 0.000 in the intervention group and from 5 to 96.4% (p < 0.001) in the index of compliance [31].

The use of fixed-dose combinations was associated with better adherence to therapy in several studies [11, 15, 16, 18, 19, 32, 33, 35, 36], including 3 randomized non-blinded controlled trials [11, 15, 32]. Two of these used the MMAS-4 [11, 15] and the other a compliance index [32].

Non-randomized intervention studies

Five studies evaluated so-called “patient education” or similar interventions [19,20,21,22,23]. Those using the MMAS-4 reported increases from 2.80 to 3.79 points (p < 0.0001) [19] or from 1.8 to 3.9 points (p = 0.0002) [23], while the proportion of patients with an MMAS-4 of 4 points increased from 38.6 to 57.9% (p = 0.04) [21]. Adherence, as measured by a bespoke questionnaire improved from 27 to 67% (p < 0.05) [20]. The proportion of patients who reported measuring their BP daily increased from 28.8 to 65.4% (p < 0.05) and taking antihypertensive drugs daily increased from 38.5 to 82.7% (p < 0.05) [22].

The use of fixed-dose combinations of antihypertensive drugs was evaluated in 7 non-randomized studies [16,17,18,19, 33, 35, 36]. As in the randomized trial studies, fixed-dose combinations were associated with significant increases in adherence, as measured by the MMAS-4 compared to baseline [16,17,18,19, 33, 35].

Using bespoke questionnaires, consistently high adherence was observed during the first year of treatment with a fixed-dose combination of an angiotensin converting enzyme inhibitor and calcium channel blocker, at 97 and 93% at 6 and 12 months respectively [36].

Critical appraisal/study quality assessment

Problems included the small number of randomized studies none of which were blinded, heterogeneity of patient groups in non-randomized studies, small sample size in some studies, heterogeneity of samples, presence of concomitant pathology, use of subjective methods of assessing adherence (questionnaires), and incomplete presentation or selective reporting of results [42].

Discussion

This is the first scoping review of Russian language studies on adherence to AHT. Our search strategy was designed to include as many primary publications as possible, although it was concerning that abstracts for a large number of studies could not be located. This highlights an issue that has not, to our knowledge, received adequate attention so far. There are a large number of regional medical journals, printed in small numbers, and while their tables of contents are available electronically, their content (including abstracts) is not. There is no central repository. While, in theory, it might be possible to obtain copies from publishers, the logistical barriers would be formidable and, given the methodological weaknesses reporting in many of the papers obtained, unlikely to be commensurate with the information that might be extracted from them.

In accordance with the questions and objectives in this scoping review, the key findings are as follows. Adherence was assessed using MMAS-4 in 18 studies and in other studies using bespoke questionnaires. In the Russian population, the baseline MMAS-4 scores varied from 1.62 ± 0.27 points [11] to 3.12 ± 0.86 points [35]. The proportion of patients with 4 points on the MMAS-4 varied from 11.1% [15] to 44.2% [35], while in studies using a bespoke questionnaire, the frequency of adherence varied from 23.3% [40] to 74.9% [38]. The latter were patients attending an outpatient cardiology clinic. Relatively low levels of adherence were observed in most studies [11, 20, 22, 23, 31, 32, 37, 40, 41]. These findings are consistent with a cross-sectional study by Cybulsky et al. on 1068 working-age men in Izhevsk, Russia, which reported 41% of patients taking antihypertensive drugs daily [43].

Many studies included quite large samples, from several hundred to several thousand people [12, 13, 16,17,18,19, 24, 26, 29, 35, 38, 39], but some were much smaller, from 30 to 75 people [11, 15, 20, 22, 25, 30,31,32, 36, 37, 40]. The follow up period varied from 6 weeks [23] to 12 months [12, 13, 36, 37]. One study lasted 4 years [16], but follow up data were unavailable for analysis.

Studies of determinants of adherence identified being female [29, 33, 35, 38, 41], age over 50 years [29, 33], not living alone [29, 38], employment [27, 33], higher education [33], and living in a city [41], comorbidity including: ischemic heart disease [24, 29, 38], history of myocardial infarction [26, 29], arrhythmias [27], and diabetes mellitus [24, 29, 35]. These are consistent with previous systematic review of studies from elsewhere [44]. Data of association with anxiety level, panic attacks and subclinical depression [19] differ from those in the publication [44].

Evidence for an association between eligibility for the MAS, grade of HT, and experience of hypertensive crisis was inconclusive [24, 27, 29, 33, 38,39,40,41]. In two [29, 40], patients with a higher BP were more adherent and in another two [27, 33] better adherence was observed in patients with a lower grade of HT. In one [41], patients who had experienced a hypertensive crisis had higher adherence but in another [39] adherence was lower. There were also conflicting findings on associations with duration of HT. In three [29, 38, 40] patients with a long history of HT were more adherent but the reverse was observed two [27, 39]. One reason for such discrepancies could be heterogeneity of patients included. In addition, sample sizes varied greatly, with 1419 [38, 39], n = 161 [27], n = 190 [41] and n = 30 [40]. There was no evidence that adherence was associated with income and physical activity [29].

Almost all interventions studies found significant results, possibly reflecting publication bias. They included optimization of the drug regimen [11, 15, 16, 18, 19, 32, 33, 35, 36], an educational program [12, 13, 19,20,21,22,23], provision of an automatic home BP monitor [31, 37], and an initiative to inform the patient of his or her risk [14].

Provision of an automatic BP monitor [31] and optimization of the drug regimen using fixed combinations [11, 15, 16, 18, 19, 32, 33, 35, 36] found to be effective elsewhere [45, 46], were associated with a significant increase in adherence to AHT. However, in several of the studies adherence also improved in control groups, most likely because both groups received a series of enhancements to treatment including self-monitoring diaries, and written recommendations on lifestyle changes, as well as intensive monitoring of both groups for the entire period of follow-up. Thus, two of the randomized controlled studies found no differences between intervention and control groups, in adherence or BP reduction [31, 32]. The authors of two studies [11, 15] concluded that the results support fixed-dose combinations, but this seemed difficult to justify from their findings.

Strengths and limitations

The randomized trials included, none of which were blinded, had a high risk of systemic error (bias), while using questionnaires that subjectively measure adherence and reporting disparate numbers of patients in the intervention and control groups [37], including only non-adherent patients [12, 13], and in two randomized non-blinded controlled trials no baseline adherence rates were reported (incomplete data presentation) [14, 37]. As a consequence, the risk of a systemic error in our review is close to critical.

In the vast majority of studies, the antihypertensive effect of adherence was measured as mean BP or probability of achieving target BP levels. Only one study measured 24-h BP [30] or used home BP monitoring [37].

Most studies used subjective methods of assessment, namely questionnaires, including some developed by the authors themselves, with no information on their testing or validation. The only objective method used for assessing adherence was indirect, using pill counts.

This situation is regrettable, because other methods for assessing adherence exist, differing in the degree of objectivity and information provided. The subjective methods include, first, various validated questionnaires, among which the MMAS-4 is most often used [47]. Subjective methods of assessing adherence, based on a patient’s self-assessment, should be used with caution. Adherence rates are overestimated by up to 20% compared with an objective assessment [47]. Objective indirect methods of assessing adherence include pill counts, as well as various electronic dispensers [48]. Electronic prescription and claims data on medication dispensed has also been used to evaluate an adherence, assessed by the proportion of days covered, although obviously it assumes that medicines dispensed are actually taken [49, 50]. Abroad, a way of controlling adherence is available, such as the analysis of electronic databases of pharmacy chains [51]. The “gold standard” for assessing adherence is measurement of drugs in biological fluids, for example, in blood or urine, with the latter preferred as it is less invasive [52].

Our findings suggest that interest in this issue is increasing among Russian researchers. There were 85% more publications in the period 2013 to 2017 than in the previous five-year period. However, the methodological quality of the papers has not improved. There is no obvious improvement in study design, with no more randomized trials and although the MMAS-4 questionnaire has been used more often, the recent increase in studies cannot be considered a major achievement.

Notwithstanding the many methodological weaknesses, these findings suggest a picture of unsatisfactory adherence to drug treatment in the Russian hypertensive population. However, the quality of studies of adherence to AHT is a serious problem not only in Russia, but also internationally. The 2014 Cochrane review of interventions to improve adherence [53] found only 13 studies on AHT that were suitable for inclusion. It noted the unsatisfactory (poor) overall level (quality) of such studies and emphasized the need to use objective indicators of adherence. For this purpose, Ascertaining Barriers for Compliance project was developed [54], as well as Emerge’s recommendations, that was published in order to solve the lack of standard methods to assess adherence [55].

There were the limitations of the scoping review process, e.g. last search dated was 2017, and reports published only in the Russian language.

Despite the limitations of most of the studies included this review makes a contribution in the following respects.

First, it is the first attempt to scope a comprehensive picture of the Russian literature on this topic. An important contribution of this paper is that it captures the full spectrum of research on adherence in Russia. It has identified some large studies, with prolonged follow up, using internationally accepted measures. Collectively, the small number of better quality studies does offer insights that can help inform the design of relevant policies, although further evidence is essential. Adherence to AHT in Russia is clearly a problem. Given the considerable economic burden that this creates, borne by both patients themselves and the health system as a whole, this is an issue that should be considered a high priority.

Second, the evaluative studies do point to some potentially promising measures. However, all should be subject to further evaluation and there is a clear need for much more research on interventions that have been found to be promising elsewhere [56,57,58].

Conclusions

The main determinants of adherence to AHT are sociodemographic factors, such as female gender, age over 50 years, not living alone, employment, higher education, and living in a city; comorbidity, including: ischemic heart disease, history of myocardial infarction, arrhythmias, diabetes mellitus, and psychiatric disorders; adherence was also associated with onset of HT at a young age and use of fixed dose combination therapy. The findings of studies of the association between adherence and grade of HT, experience of hypertensive crisis, and duration of HT were not consistent. Patient education, telephone reminders, home BP monitoring and fixed-dose combinations of drugs are most important for improving adherence. The interpretations of these findings are limited by unreliable measures of adherence. It is necessary to introduce objective methods for assessing of adherence. A central repository of studies published in regional medical journals should be created.