Impact of educational interventions in reducing diabetic complications : a systematic review

ABSTRACT Objective: To identify in the literature evidence of the effectiveness and effi cacy of educational interventions in reducing metabolic and/or vascular complications in adults with diabetes mellitus. Method: A systematic review performed in LILACS, IBECS, CUMED, CINAHL and Medline databases and in the online library SciELO with studies published from 2004 to 2014. Results: Eleven studies were included (5 randomized clinical trials and 6 quasi-experimental). We only identifi ed studies that analyzed vascular complications. Conclusion: Two clinical trials demonstrated effi cacy in reducing cardiovascular complications, of cataract or retinopathy and nephropathy and all the quasi-experimental studies showed effectiveness in reducing feet ulcers, peripheral neuropathy and vasculopathy, and maintenance of kidney function. Descriptors: Health Education; Evaluation of the Effi cacy-Effectivenessof Interventions; Diabetic Complications; Diabetes Mellitus Type 1; Diabetes Mellitus Type 2.


INTRODUCTION
Chronic non-communicable diseases (NCD), such as diabetes mellitus (DM), hypertension, and chronic obstructive pulmonary disease, occupy the top positions in the world mortality statistics: it is estimated that 73% of deaths in 2020 will be caused by such diseases (1) .Approximately 347 million people worldwide have DM, 90% of type 2 (2) .It is estimated that this number will have increased to 353 million in 2030, making it the 7 th leading cause of death (3) .
From 2008 to 2010, DM and its complications accounted for 10.3% and 36.6% of the total number of hospitalizations in the Brazilian Unified Health System, with a mean cost of R$1,302 to R$1,315 per hospitalization, respectively.Among the major complications of the disease, there are acute metabolic dysfunction (ketoacidosis and hypoglycemic coma), microvascular dysfunction (nephropathy, retinopathy, and neuropathy) and macrovascular dysfunction (peripheral vascular disease, coronary artery disease, and cerebrovascular accident) (4) .
As characteristic to chronic NCDs, DM treatment is complex, as it depends directly on patient education and active participation in the care plan to achieve glycemic control and prevent complications (5) .Patient education can be operationalized through different strategies, to improve their outcomes.
In the last ten years, Cochrane systematic reviews on the effectiveness and efficacy of educational interventions for individuals with diabetes in different contexts have been found in the literature: management of blood glucose, blood pressure, body mass index, and cholesterol (6)(7) , self-efficacy and empowerment of the patient regarding disease control (7) , knowledge on DM, smoking cessation, self-management concerning diet and psychosocial outcomes (6) , and foot care and prevention of fungal infections (8) .However, only one systematic review assessed the effectiveness of education in the prevention of vascular diabetic complications (8) .
In this context, we question: what is the efficacy and effectiveness of educational interventions in reducing metabolic and/or vascular diabetic complications in adults with DM?The answer to this question will assist health care professionals in the choice of suitable teaching methods for better clinical outcomes for patients.Therefore, the objective of this study was to identify, in the literature, evidences of the effectiveness and efficacy of educational interventions in reducing metabolic and/or vascular diabetic complications in adults with DM.

METHOD Ethical aspects
Due to free access to studies included in this review, as they are not documents that require ethical secrecy, no assessment by the Research Ethics Committee was necessary.

Study design
A systematic literature review, according to the flow chart of the "Preferred Reporting Items for Systematic Reviews and Meta-Analyses" (PRISMA) (9) , including experimental or quasiexperimental, primary, quantitative studies.Educational interventions of randomized clinical trials were evaluated as to efficacy, and those of quasi-experimental studies were evaluated according to effectiveness.

Inclusion criteria
Scientific articles available with full version available in English, Portuguese, or Spanish published from 2004 to 2014.This period was chosen due to the publication of the International Standards for Education on Diabetes by the International Diabetes Federation, at the end of 2013.The document contains instructions on essential information for health professionals on diabetes and its management, so the application of this knowledge and the acquisition of skills improved the care and promoted the achievement of positive outcomes for people with diabetes (10) .The search was conducted in October and November 2014, in the primary Latin American and Caribbean Literature on Health Sciences (LILACS), Spanish Bibliographic Index of Health Sciences (IBECS), CUMED, Cumulative Index to Nursing and Allied Health Literature (CINAHL) and Medline databases, and in the Scientific Electronic Library Online (SciELO).

Search strategy
The search strategy was defined by means of PICO (11) , using the Health Science Descriptors (DECS), Medical Subject Heading (MeSH), and CINAHL Titles with the Boolean operators OR and AND, as shown in Box 1.
It is important to highlight that element C of the PICO strategy was not addressed, as the aim of this study was not to compare interventions.To ensure that the largest possible number of references was found, we decided to use filters for adults instead of descriptors or keywords, since, often, the age groups studied are not included as descriptors.The searches were conducted using the strategies on Box 2. CORRESPONDING AUTHOR eficacia en la reducción de complicaciones vasculares, de la catarata o retinopatía y de la nefropatía; y todos los estudios cuasiexperimentales revelaron efectividad en la reducción de las úlceras de pie, la vasculopatía y la neuropatía periféricas, y en el mantenimiento de la función renal.Descriptores: Educación en Salud; Evaluación de Eficacia-Efectividad de Intervenciones; Complicaciones de la Diabetes; Diabetes Mellitus Tipo 1; Diabetes Mellitus Tipo 2.

Selection of articles
Selection of articles was performed through analysis of title, followed by reading the abstracts for the identification of those which would be fully read, independently, by two researchers.Data were extracted from the final sample by means of an instrument containing identification data (authors, year and country of publication), study design, sample/population size, mean age of participants, mean time of evolution of DM, educational intervention performed, results, and conclusions.

Assessment of the methodological quality of studies
It was performed by two researchers, for purposes of description and not for exclusion from sample.To assess the quality of the randomized clinical trials, the Jadad Scale was used, which consists of three items directly related to research bias reduction (randomization, blinding, and destination of all participants), totaling 5 points.Studies are classified as of poor quality if the score is less than 3 (12) .
For quasi-experimental studies, this evaluation was performed using Downs & Black's criteria.The original questionnaire contains 27 questions, totaling score of 32 points, divided into four groups: presentation (evaluates items such as clarity in the description of the objectives, variables of confusion, probability values); external validity (related to extrapolation of the data to the population from which the sample was planned); internal validity (analysis of biases, reliability of exposure and outcome measures and use of confounding variables); and power of the study (13) .Of the 27 items originally proposed by the authors, 6 were excluded, remaining 21 questions, with maximum final score of 24.Such items were excluded because they referred to side effects of interventions (since there are no side effects arising from educational interventions) or to aspects inherent to randomized clinical trials or case-control studies (randomization, blinding, comparison with control group).The cut-off point used to consider the study of good quality was of 12 points (>50% of the maximum score), according to criteria established in systematic review (14) .

Analysis of the results
Data were presented in descriptive form and classified according to the outcomes/complications evaluated by the studies included in this review.Due to the heterogeneity of the interventions and of the characteristics of the study samples, it was not possible to perform meta-analysis.
Three of the five randomized clinical trials (15,(20)(21) were considered to be of quality and five of the six quasi-experimental studies (16)(17)(18)(22)(23) were classified as of good quality.

Professionals who implemented the interventions
One study had no report on which professionals implemented the educational intervention (24) .Participation of nurses in the interventions was significant, as they were present in 80.0% of investigations (15)(16)(17)(18)(19)(20)(22)(23) . Some stuies showed the multidisciplinary work through the participation of different professional categories in the interventions: physicians and nurses (16,19) , physicians and nutritionists (19) , and occupational therapists and nurses (20) .Two researches had participation solely of physicians (21) and physical therapists (25) in the educational interventions aimed at diabetic persons.

Effectiveness and efficacy of interventions in reducing diabetic complications
Of the 11 studies identified, two clinical trials showed efficacy of the intervention in reducing complications related to the cardiovascular system (21) , cataract or retinopathy, and nephropathy (19,21) (Box 3).All quasi-experimental researches showed effectiveness of interventions: reduction of feet ulcers (17,22,24) , of peripheral vasculopathy (16) and of peripheral neuropathy (18) , in addition to the maintenance of kidney function (23) (Box 4).
Regarding interventions with positive impact on reduction of complications, most were implemented exclusively by nurses (15,(17)(18)(22)(23) or in partnership with other professionals (16,(19)(20) . One stdy had participation solely of physicians (21) . There wasno similarity among mean age or time of evolution of DM in patients in the different studies.Most effective or efficient interventions consisted of individual sessions (18)(19)(20)(21)(22)(23) .One study involved the community group in sessions (16) and another included the patient's family (24) . Twoinvestigations included customized interventions with interval between educational sessions according to the risk profile of patients or presence of diabetic neuropathy, peripheral artery disease and/or deformity, history of ulcer or foot amputation (17) and use of orthoses (24) .One included telephone contact and practical training as associated measures (22) and two implemented only telephone contact as an adjuvant measure (16,23) .Chao et al. (19) , 2014

DISCUSSION
This study sought evidence as to the impact of educational interventions on reduction of vascular and metabolic complications related to DM.However, only studies that analyzed vascular complications were found, which may be associated with the importance of these complications as major causes of morbidity and mortality in patients with DM (7) .
Adherence to behavioral and lifestyle modification promoted by education on DM is influenced by time of disease.A study showed that individuals with DM for less than one year showed greater adherence to proper dietary habits and to physical activity and lower levels of glycated haemoglobin after 3 years of follow-up (26) .On the other hand, patients with DM 2 diagnosed for over 20 years would have worse metabolic control due to low adherence to treatment regimen, evolution of disease with progressive dysfunction of beta cells, and no adjustment of medications when compared with those diagnosed for less than five years (27) .Thus, it is not possible to know if the evolution of DM may have influenced the negative results obtained by the studies which contained no information concerning the time of disease (15,18,20) .
Investigations indicate that inadequate management of blood glucose level is a factor associated with the presence of feet ulcers (28) and with amputation among individuals with diabetic foot (29) .However, it is important to analyze the influence of educational interventions on outcomes associated with complications of DM, in addition to the specific serum levels of glucose or glycated hemoglobin.Thus, we reinforce the importance of this review, whose results will be discussed according to the microvascular and macrovascular complications of DM.
Diabetic peripheral neuropathy, characterized by pain, paresthesia, and sensory loss, affects approximately 50% of patients with DM both of type 1 and of type 2 (32) .Diabetic nephropathy affects approximately one-third of people with DM in the world, being the leading cause of terminal renal failure associated with cardiovascular diseases and increase of mortality of patients (33) .
For reduction of these complications, the majority of studies in this review (18)(19)(20)(21)(22)(23) used individual sessions as strategy during the educational interventions.The individual sessions and evaluations strengthen the link with the professional, who gets to know the individual and his/her care management practices.Thus, in partnership, it is possible to develop autonomy of care (34) .On the other hand, telemonitoring, implemented by four studies included in the review (16,20,(22)(23) , provides care, acquisition of knowledge, and reflection on self-care, being adjunct in interventions (35) .
Impact of educational interventions in reducing diabetic complications: a systematic review Menezes MM, Lopes CT, Nogueira LS.
Macrovascular complications: cardiovascular diseases (21) , peripheral vasculopathy (16) , feet lesions (22) and ulcers (15,(17)(18)20,24) , and amputations (18,20) Diabetes macrovascular disease is characterized by structural and functional changes in large arteries (7) . The ntervention implemented in the study with longer follow-up (7.7 years) identified in this review (21) was efficient in reducing the occurrence of cardiovascular events. The sty conducted with fishermen and farmers showed, after the educational intervention, improvement of ankle-brachial index (16) , considered a measure of verification of peripheral obstructive arterial disease (36) .
Sensory loss secondary to peripheral diabetic neuropathy, at times, goes unnoticed by the patient and the first presentation can be feet ulcer (32) .In Brazil, the rate of amputations among individuals with diabetic foot reaches 58.2% (29,37) .In addition to inadequate control of blood glucose, other factors associated with amputation include: lack of feet examination during the most recent medical consultation, lack of instructions on the care of feet in the consultations held the previous year, and non-adherence to pharmacological treatment according to medical advice (29) .In fact, in the United States, there is a regional variation of rates of amputations of the lower limbs: in areas where there is participation of individuals with DM in classes on self-control of the disease there is fewer occurrences of amputations when compared to regions where this participation does not occur (38) .
Patients with DM and ulcers on the feet have worse quality of life in the physical, social, and psychoemotional domains (39) .The DM of long evolution (on average 12.5 years) and without proper control contributes to the occurrence of ulcers.Similarly, other factors associate with the presence of feet ulcers, as the absence of plantar tactile-pressure sensitivity, thick nails, and calluses (28) .Hence, it is inferred that educational interventions that improve the care of the feet not only reduce the chance of developing ulcers in those regions, but also promote the quality of life of patients.
Verifying patient compliance to the instructions is also an important item that influences the clinical outcomes.A study carried out in the rural area of the state of Ceará with older adults of the System of Registration and Follow-up of Hypertensive and Diabetic Persons showed low adherence in selfcare of the feet, as 70.3% of the patients with DM wore slippers, 55.0% used no moisturizer, and 74.0%clipped the nail improperly and did not dry the interdigital region after washing (40) .One of the studies in this review (24) found that the recurrence of feet ulcers was less frequent and the healing process faster among those who adhered to the program, despite the mean evolution of DM in these patients being long (13.7±7.6 years).
The results found in this review concerning the occurrence/ recurrence of feet ulcers after educational interventions were contradictory: some studies showed effectiveness (17,22,24) of the actions, while others showed they were not effective (18) nor efficient (15,20) .
It is noteworthy the difficulty to compare and summarize the results of studies included in this review, since there was no similarity in the designs of educational interventions.In addition, the complications, while outcomes, were evaluated by means of different methods, not always validated, and after different follow-up periods.
In this sense, it is understood that the effectiveness of the quasi-experimental studies should be confirmed in future randomized clinical trials, with the aim of reducing the risks of biases related to selection and to measuring, thus proving the efficacy of the educational interventions.Nevertheless, the results of this review indicate possible models of educational interventions to be tested by health professionals to reduce diabetic complications.
Some limitations of this review should be considered: the restricted period covered by the data and the inclusion of articles available only in English, Portuguese, or Spanish.

CONCLUSION
This review determined that the combination of different educational interventions provided individually or in group to adult patients with DM has influence on reduction of vascular complications.Efficient interventions involved individual sessions of education on DM and instructions on self-care conducted by physicians or multidisciplinary staff (physicians, nurses, and nutritionists).These actions improved nephropathy, cataract, retinopathy, peripheral neuropathy, and cardiovascular events.Effective interventions included individual strategies, involving meetings and telephone contacts conducted by nurses who provided instructions on foot care, diet, exercise, stress control, and drug therapy.Such strategies reduced, mainly, the frequency of peripheral neuropathy, the lesions on the feet, and the worsening of kidney function in patients.
However, there is a gap in the literature concerning the effectiveness and efficacy of educational interventions, since no study makes reference to metabolic complications.Therefore, there is evident need for future randomized clinical trials that analyze the impact of these actions in the prevention of diabetic complications, particularly metabolic ones.

Figure 1 -
Figure 1 -Flow chart of the process of selection of studies according to PRISMA, São Paulo, Brazil, 2014 Box 2 -Search Strategies used in databases,2004-2014 Impact of educational interventions in reducing diabetic complications: a systematic review Menezes MM, Lopes CT, Nogueira LS.Impact of educational interventions in reducing diabetic complications: a systematic review Menezes MM, Lopes CT, Nogueira LS.Characteristics of the quasi-experimental studies on the effectiveness of educational interventions on the outcomes investigated, São Paulo, Brazil, 2004-2014 Notes: TCA: transluminal coronary angioplasty; CHOL: cholesterol; CABG: coronary artery bypass graft surgery; CV: cardiovascular; DM: diabetes mellitus; DM 1: diabetes mellitus type 1; DM 2: diabetes mellitus type 2; NR: normality range; CG: control group; IG: intervention group; AMI: acute myocardial infarction; N: normal; NS: nonsignificant; GFR: glomerular filtration rate Box 3 (concluded)