The role of concordant and discordant comorbidities on performance of self-care behaviors in adults with type 2 diabetes: a systematic review

Introduction

Diabetes mellitus (DM) is one of the largest global health challenges of the 21st century as the number of cases continues to rise.¹ The epidemic is mainly from type 2 diabetes mellitus (T2D) that is driven by genetic, epigenetic, environmental, and behavioral factors such as sedentary lifestyle, consumption of energy dense diet and obesity.^1–3 According to the International Diabetes Federation (IDF), about 425 million people between 20 and 79 years of age lived with DM in 2017 worldwide.⁴ The global age-standardized diabetes prevalence is 9.0% in men and 7.9% in women though there is great regional variation.⁵ More than 90% of all DM cases are T2D which is continuously increasing.^4,6

Patients with T2D have a higher number of comorbid conditions, also referred to as multimorbidity, which may result in treatment conflict,⁷ reduced glycemic control,^8,9 increased cost of treatment,^10,11 and lower quality of life.¹² Multiple studies in T2D have demonstrated multimorbidity prevalence rate as high as 97.5%.^{7,8,10,13–16} Studies show that low socioeconomic status, obesity and job strain,¹⁷ age, race/ethnicity,¹⁸ and low health literacy¹⁹ are associated with increased prevalence of comorbidity in T2D. Furthermore, about 50% of T2D patients face premature mortality from cardiovascular comorbidities such as coronary artery disease, heart failure and stroke, and approximately 10% from renal failure.²⁰

The successful management of T2D requires a patient’s engagement in self-care on a daily basis to control its progression and to prevent serious complications, reduce rates of hospitalization and cost of care, and improve quality of life.^21–24 Diabetes self-care involves sustained engagement in multidimensional behavioral actions including healthy dietary intake, physical activity, blood glucose monitoring, medication adherence, problem solving, and risk reduction such as foot checks and smoking cessation.^25,26 Antecedent factors such as demographic, psychosocial, clinical, and environmental variables can influence the patient’s successful performance of diabetes self-care.^26–28 The influence of these factors may become even more important when there is another serious comorbid condition or if multimorbidity exists.

There is a need for further research to understand the impact of comorbidities on optimal diabetes self-care in order to maximize self-care for patients with T2D and multimorbidity.²⁹ Guidelines currently are primarily disease-specific and provide little direction for self-care for T2D in the presence of other chronic conditions.³⁰ Interventions that target self-care for T2D in the presence of multimorbidity are also limited. Understanding the relationship between diabetes self-care and other chronic conditions may lead to more effective interventions for this complex population.^31–33

A framework developed by Piette and Kerr³⁴ that conceptualizes chronic conditions as concordant or discordant with diabetes care has gained momentum over the last decade to help guide management of T2D and coexisting multimorbidity. Diabetes-concordant comorbidities (such as cardiovascular, metabolic and renal disease) share parts of the same overall pathophysiologic profile and care management as T2D. For example, blood pressure and lipid monitoring are overlapping cardiovascular risk reduction goals for diabetes and cardiovascular disease and likely to lead to better outcomes for both conditions. Magnan and colleagues³⁵ found that having more concordant conditions was linked to better quality of care for diabetes.

Diabetes-discordant comorbidities have no direct relationship with diabetes in their pathophysiologic profile or care management and include chronic conditions such as asthma, cancer and mental illness such as depressive symptoms.^35–40 Treatment for some of these discordant conditions might interfere with treatment for T2D. For example, using steroids for asthma treatment would increase blood glucose and conflict with the treatment for diabetes while depressive symptoms have been shown to lead to poorer adherence to self-care in chronic conditions, including T2D.Time limitations, conflicting care goals, and other challenges may result in a lower quality of care for diabetes and the discordant condition as compared to having concordance or a single condition. Using a Delphi study method, Magnan and colleagues³⁸ identified 12 concordant and 50 discordant comorbidities in DM. The findings from this study suggested that concordant chronic conditions are more easily managed because care goals are similar and more likely to be identified and addressed by care providers. However, Magnan and colleagues³⁵ noted that the presence of more dominant concordant conditions such as advanced heart failure may reduce diabetes self-care behaviors; others have not shown this effect. Discordant conditions are less likely to be identified and included in care goals which may contribute to poorer diabetes control, additional complications, and higher health care utilization.

The role that the concordance-discordance framework may have in identifying key determinants or challenges in diabetes self-care has received little attention in the literature. Awareness of obstacles faced by patients with T2D who are managing multiple chronic conditions will help inform future strategies for more effective diabetes self-care. The purpose of this systematic review was to examine the role of diabetes-concordant and discordant chronic conditions on the performance of self-care behaviors in adults with T2D.

Methods

The process of conducting and reporting this systematic review was guided by the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statements.^41,42 The PICO (Participant-Intervention/Exposure-Comparison-Outcome) format was used to guide the research question and to establish inclusion and exclusion criteria for articles in this review.

Search strategy

The construction of the search strategy in this review was based on the guideline developed by the Joanna Briggs Institute (JBI).⁴³ A total of 68 search terms were used. Examples include: “Type 2 diabetes,” “adult,” “comorbidity,” “concordant comorbidity,” “discordant comorbidity,” “multimorbidity,” “myocardial infarction,” “cerebrovascular disease,” “heart failure,” “chronic renal failure,” “asthma,” “depression,” “self-care behavior,” “self-care,” “diet,” “physical activity,” “foot care,” and “medication adherence.”Medical subject heading (MeSH) and free text words were used for searching the databases. Truncation and Boolean operators – AND/OR – were used to combine the different search terms. Finally, the search was refined by publication date (March 2006 to April 2018), English language, and study design (cross-sectional survey, case-control, cohort, non-randomized clinical trial, and randomized clinical trial).

Studies were identified by searching the following electronic databases: PubMed, CINAHL, PsycINFO, ISI Web of Science, and EMBASE. Further search of Google Scholar, Cochrane Library, and websites of pertinent organizations such as World Health Organization (WHO), International Diabetes Federation (IDF), and American Diabetes Association did not yield one additional study. However, scanning of the reference lists of the retrieved articles provided two additional studies. The literature search was grouped into the following comorbidity categories: concordant comorbid conditions only; discordant comorbid conditions only; and both concordant and discordant comorbid conditions.

Inclusion and exclusion criteria

Only quantitative studies that examined the relationship between concordant and discordant comorbid conditions and diabetes self-care behaviors in adults (≥18 years) with T2D were included in this review. Studies that addressed either overall diabetes self-care behavior or specific self-care behaviors such as diet, medication, blood glucose self-monitoring, exercise, foot care, and smoking as an outcome variable were included. Studies not available in English, conference abstracts and books were not included in the review. The time frame for selection of articles was informed by the publication of a conceptual framework for understanding diabetes care in the context of concordant and discordant comorbidities.³⁴

Study selection

All articles retrieved from the search process were saved into the Endnote citation manager. Duplicates were removed, and the remaining records were screened for study inclusion. Eligibility was assessed independently in an unblinded standardized manner by 2 reviewers. Disagreements between reviewers were resolved by consensus. A two-stage screening process was undertaken using a checklist we developed for this purpose. First, the titles and abstracts of the articles were screened for relevance in relation to the PICO question. In the second round, full-text screening was performed. After screening, the studies were assessed for methodological quality in a two-step process. In the first step, the Joanna Briggs Institute (JBI) Critical Appraisal Tools⁴⁴ was used to determine to what extent a study had addressed possible biases and included the PICO of interest in this review. In the second step, the remaining studies were rated as strong, moderate, or weak using the Quality Assessment Tool for Quantitative Studies⁴⁵ in six domains: selection bias, design, confounders, blinding, data collection methods and withdrawals and dropouts. The overall rating for the study was decided by assessing the six domain ratings. Those with no weak ratings and at least four strong ratings were considered strong evidence. Studies with less than four strong ratings and one weak rating were considered moderate while those with two or more weak ratings were considered weak evidence.

Data collection

Data were extracted using a standardized grid format that followed recommendations from the Cochrane Review⁴⁶ and the Joanna Briggs Institute.⁴⁷ Information related to data source, setting, study aim, design, sample characteristics, comorbidities types, outcome measurement, and results were extracted from individual studies.

Data analysis and synthesis

A narrative synthesis method was used in this systematic review because the heterogeneity observed in the study designs and methods of the selected studies did not allow the application of pooled analytical meta-analysis procedures. A narrative synthesis organizes and summarizes studies using words to explain the findings.⁴⁸ In this review, the use of a narrative approach facilitated description of concordant, discordant or the presence of both conditions in T2DM which helped to compare the impact of each on diabetes self-care.

Result

The initial database search identified 1,136 articles. However, only 33 studies met the inclusion criteria and were included in this review. The number of studies excluded at each stage of duplication removal, screening, and eligibility assessment process is shown in Figure 1.

Figure 1 PRISMA flow chart.

Study characteristics

Table 1 provides a summary of the 33 studies meeting eligibility criteria and included in the systematic review. Most studies included T2D self-care with discordant comorbidities (n=23) compared to self-care with concordant chronic conditions (n=6). Four studies included T2D self-care with both concordant and discordant chronic conditions. Twenty one studies were cross-sectional,^49–69 eight were cohort studies,^70–77 two were case-control studies,^78,79 one was non-randomized intervention,⁸⁰ and one was randomized controlled trial.⁸¹ Seventeen studies were conducted in the United States (US), four in Canada, two studies each in Malaysia, China and Ireland, and one study each in the Netherlands, Australia, Belgium, Romania, and Jordan. The sample size of the studies ranged from 64 to 740,197 with a median of 615. The studies reported the mean age of the participants ranging from 47.7 to 70.8 years. One study was rated as weak, 27 as moderate, and five as strong.

Table 1 Summary of the characteristics of studies included in the review

Twenty studies measured generic or overall diabetes self-care behavior as an outcome. Specific diabetes self-care behaviors were also measured as an outcome and included: medication adherence (N=9), exercise behavior (N=4), dietary behavior (N=2), foot care (N=1), blood glucose monitoring (N=1), and smoking behavior (N=1).

Concordant and discordant comorbidities

The most frequently measured T2D concordant and discordant comorbidities in relation to self-care behaviors are shown in Table 2. Hypertension, obesity and chronic kidney disease were the most frequent concordant conditions with heart failure being the least frequently measured. Depression was the most frequently measured discordant comorbidity.

Table 2 Comorbid conditions investigated by the studies included in this review

Frequency of diabetes self-care behaviors in concordant and discordant comorbidities concordant

Medication adherence was the most frequently reported self-care behavior for concordant conditions. Two of the four studies that focused on medication adherence in concordant comorbid conditions described that more than 50% of their participants were adherent.^62,73 The other two studies, however, reported that compared to those without comorbid conditions, T2D patients with concordant comorbidities including hypertension, dyslipidemia and obesity were 1.78 (95% CI=1.064, 2.981) times less likely to be adherent to the medication regimen⁴⁹ and less likely to be physically active (β=−0.32, p<0.0001).⁶⁵ Another study evaluating foot self-care in adults with T2D reported that those with hyperlipidemia were 38% less likely to perform the recommended foot self-care for ≥6 days per week.⁵¹ A randomized controlled trial tested the effects of a telemedicine intervention (Informatics for Diabetes Education and Telemedicine Project) on adherence over time in older Hispanic and African Americans reported that greater comorbidity over time had worse adherence to diabetes self-care activities (β=−0.0204, p=0.01) compared to those without comorbidities.⁸¹

Discordant

The most common self-care behavior reported for discordant conditions was also medication adherence followed by dietary and physical activity. Only three studies reported the mean score of the overall diabetes self-care activities.^50,56,79 AmongT2D patients with discordant comorbid depression, the overall mean diabetes self-care score ranged from 3.87 to 40.5. This shows the mean of total diabetes self-care score on the Summary of Diabetes Self-Care Activities (SDSCA) for diet, exercise, medication, blood glucose monitoring, foot care, and smoking cessation which indicates less diabetes self-care performance. Two additional studies also reported that only 50% of their study participants practiced diabetes self-care behaviors in the presence of depressive symptoms.^69,70

Regarding specific diabetes self-care behaviors, four studies examined depressive symptoms and found that taking prescribed medications was the most frequently performed while exercise was the least often performed.^50,52,59,79 In contrast, another study investigating depressive symptoms reported that taking medications as prescribed was the most frequently performed self-care behavior (M=6.01±1.84) during the week, followed by exercise (M=2.77±1.78) and blood glucose self-monitoring (M=1.38±1.59).⁵⁶ Johnson and colleagues⁶⁰ examined dietary and physical activity behaviors among adults with diabetes-related distress and depressive symptoms. In this study, only 42% had good adherence to the recommended diabetes dietary recommendations and almost 80% did not meet physical activity guidelines. Participants with depressive symptoms were 5.2 less likely to adhere to dietary guidelines compared to those without depressive symptoms, but this was not independently associated with physical activity level.⁶⁰ Persons with mild anxiety symptoms and moderate to severe anxiety symptoms were 1.4 times and 1.7 times more likely to report being physically inactive than persons without anxiety symptoms, respectively. Feil and colleagues⁵⁷ reported that older T2D patients with greater cognitive impairment were less likely to adhere to exercise (p<0.05), diet (p<0.01)or check feet for wounds (p=0.01) compared to those without cognitive impairment. In addition, as cognitive impairment worsened, adherence to each diabetes self-care behavior declined. Axon and colleagues⁷¹ examined whether depression affects medication adherence over time. Findings revealed the odds of being medication nonadherent was 1.12 times higher among those with comorbid depression compared to those with T2D alone. The same study revealed that having three or more comorbid conditions, after excluding depression, was associated with higher medication nonadherence (OR 1.09, [95% CI: 1.08, 1.10]) while having two or less comorbidities was associated with lower medication nonadherence compared to those with T2D alone.

Both concordant and discordant

Two studies that measured exercise and medication adherence behaviors in those with both concordant and discordant comorbid conditions such as depression, cognitive impairment, chronic kidney disease, and obesity found that over 62.5% of their participants did not achieve the recommended weekly moderate-to-vigorous physical activity level⁷⁷ and 30% were medication nonadherent.⁷⁶ In the anxiety study described above, if there were greater than 2 comorbidities including obesity, the likelihood of being physically inactive was almost two-fold⁶¹ compared to those without comorbidities.

Summary of concordant and discordant comorbidity and diabetes self-care behaviors

Two cohort studies^73,76 and two cross-sectional studies^51,62 reported that there were significantly higher odds of medication adherence and foot self-care in T2D patients with specific concordant comorbidities such as hyperlipidemia and coronary heart disease compared to those without these comorbidities. In contrast, two cohort,^73,77 two cross-sectional,^53,63 one case-control,⁷⁸ and one interventional⁸⁰ study reported that T2D patients with concordant comorbid hypertension, dyslipidemia, obesity, and chronic kidney disease had significantly lower odds of achieving the recommended diabetes self-care behaviors than those without these comorbid conditions.

Studies have shown the negative association between diabetes-discordant comorbidities and diabetes self-care behaviors. A cohort study⁷⁶ found statistically significant lower odds of medication adherence in T2D patients with discordant comorbidities overtime. Similarly, 14 of the 21 cross-sectional studies reviewed reported that T2D patients with discordant comorbid depression,^{54,58,59,63,64,67} diabetes-related distress,^52,60 anxiety,^35,61 schizophrenia,⁵⁵ impaired sleep quality and daytime sleepiness,⁵³ and cognitive impairment⁵⁷ had statistically significant lower odds of performing the recommended diabetes self-care behaviors compared to those without these comorbidities. The two case-control studies also reported that T2D patients with comorbid depression had significantly lower scores for diabetes self-care behaviors compared to those without depression.^78,79 In addition, five of the eight cohort studies reported that T2D patients with discordant comorbid schizophrenia and alcohol or substance use disorder,⁷⁵ diabetes-related distress,⁷⁰ and depression^{70–72,74,75} had statistically significant lower odds of achieving the recommended self-care behaviors.

In several studies, depression was mediated by self-efficacy or other factors. Among seven studies depression had no direct association with diabetes self-care behavior but was mediated by self-efficacy,^50,56,79 diabetes-related distress,^52,60 gender,⁶⁴ and health literacy.⁶⁶

Discussion

Findings from this systematic review indicate that concordant and discordant comorbidities may result in poorer diabetes self-care. To our knowledge, this is the first systematic review detailing differences between concordant and discordant comorbid conditions on diabetes self-care behaviors. The findings are consistent with previous research that multimorbidity has a negative effect on the T2D patients’ achievement of the recommended diabetes self-care behaviors. In general, there is support in the literature that concordant conditions may result in higher frequency and adherence of self-care behaviors than discordant. For example, O’Shea and colleagues⁷⁶ directly compared concordant and discordant comorbidities on oral-hypoglycemic medication adherence and determined those with concordant conditions were more adherent. Other studies, however, do not support these findings. He and colleagues,⁷³ for example, showed a positive association between peripheral neuropathy and adherence to insulin therapy, while another study showed poorer quality of diabetes self-care activities with concomitant peripheral neuropathy.⁶³ The effect of diabetes-concordant comorbidities on diabetes self-care behaviors may vary depending on the type of comorbidity and the self-care behavior being measured. For example, in the two studies reporting medication adherence with existing peripheral neuropathy,^63,73 there were considerable differences in participant comorbidity type and the self-care behaviors measured. In the He and colleagues⁷³ study, only concordant comorbidities and one specific behavior, medication adherence, was included. The Mut-Vitcu and colleagues⁶³ included both concordant and discordant chronic conditions and overall diabetes self-care behaviors were measured which may explain in part, the disparate findings.

Too much of an emphasis on the features of single comorbid illnesses may result in failure to see larger patterns in the ways that treatments for T2D and comorbidities interact.³⁸ An increased number of comorbidities was associated with a decline in diabetes self-care behaviors and is consistent with previous research.^61,71 Importantly, not all comorbid conditions are the same nor have the same consequences on diabetes self-care performance. Periodic evaluation of comorbidities, particularly as they worsen, may change patient self-care priorities from diabetes to a more dominant comorbid condition resulting in poor disease control and higher risk for complications.³⁶ The use of the concordance and discordance framework is beneficial toward this end and may help to identify which chronic conditions are most likely to result in poorer outcomes based on care goals of one of more dominant comorbidities.³⁸

Results from this systematic review support previous research concerning the negative impact of diabetes-discordant comorbidities on diabetes self-care behaviors. Most of the diabetes-discordant comorbidities involved mental health and neuropsychiatric disorders such as depression, anxiety, diabetes-related distress, cognitive decline and schizophrenia. Analyses identified that these comorbidities had a more negative impact on diabetes self-care behaviors compared to patients with T2D alone. Most of the discordant conditions were examined independently with diabetes self-care behaviors rather than with other multiple conditions which may have influenced findings. Screening T2D patients for neuropsychological multimorbidity such as depression and cognitive decline is important because they have been shown to reduce the capability of the individual to perform effective diabetes self-care. Simple screening tests such as the Patient Health Questionnaire-9 (PHQ-9)⁸² and the Montreal Cognitive Assessment (MoCA)⁸³ can be administered in clinic settings and have been previously validated in the diabetes population.

The frequency of diabetes self-care performance was lower in T2D patients with comorbid conditions compared to those without comorbidities. This is true both for the overall or global diabetes self-care behaviors and specific components including diet, exercise, blood glucose self-monitoring, medication adherence, foot care, and smoking behaviors. There is agreement among studies^52,56,59,79 that medication adherence is the most frequently performed specific diabetes self-care behaviors whereas exercise is the least performed. Thus, barriers to engagement in exercise self-care among T2D patients with comorbid conditions need to be explored in future research.

Medication adherence was the most frequently performed diabetes self-care behavior in both concordant and discordant chronic conditions, but little is known about how adults with T2D rank the importance of their specific self-care behaviors, management, and outcomes relative to those of other comorbid conditions such as hypertension or depression. A better understanding of the individual’s self-care priorities and the process used for decision-making when managing other complex chronic conditions may provide additional insight on adherence to self-care. Future research is warranted to examine which strategies best organize care for T2D patients with comorbid conditions to optimize clinical outcomes and quality of life, as well as identifying self-care priorities from the patient’s perspective. The number of adults experiencing T2D with multimorbidity is anticipated to increase making integration of care an essential component of diabetes management. Guidelines and interventions that encompass concordant conditions if they are found to be associated with improved diabetes self-care would be beneficial and help to personalize care goals. Worsened outcomes associated with discordant chronic conditions could be used to highlight areas where patients may need additional care to prevent or delay complications.^35,36

Strengths and limitations

Comparing the effect of concordant and discordant comorbid conditions on diabetes self-care behaviors was strength because no studies have previously described diabetes self-care using this approach. Using the diabetes-concordant and discordant framework can provide clinicians additional insight into which comorbid conditions may lead to better or poorer adherence to diabetes self-care behaviors. The majority of studies were cross-sectional and nonrandomized which limited the quality of evidence and interpretation of findings. Whether all confounders known to influence T2D self-care behaviors were controlled in these studies is unknown. In addition, self-reported measures were used for most studies which are less accurate and reliable. The heterogeneity of the samples, designs and measures of self-care across studies made it impossible to perform pooled analytical procedures or meta-analysis. The majority (N=26) of studies included in this review were conducted in high-income countries which limits the generalizability of the findings to middle and low-income countries where the rates of comorbid conditions may be higher in T2D.^84,85 For instance, there was no study reported from Africa concerning the effect of comorbidities on diabetes self-care behaviors.

Conclusion

Diabetes-concordant comorbidities are associated with higher adherence to diabetes self-care behaviors than discordant, but future research is needed using more rigorous designs to better understand these complex relationships with diabetes self-care behaviors. Given the increase in multimorbidity observed among patients with T2D, guidelines are urgently needed that integrate diabetes self-care with other chronic conditions, especially discordant conditions in order to optimize clinical outcomes and quality of life.

Disclosure

The authors report no conflicts of interest in this work.

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