Quality and Predictors of Diabetes Care Among Patients With Schizophrenia: A Danish Nationwide Study

In 2000, a nationwide multidisciplinary initiative was launched with the objective of systematically monitoring and continuously auditing the quality of care provided by the Danish health care system. In the following years, population-based clinical registries were established to document care for important diseases, including schizophrenia (the Danish Schizophrenia Registry [DSR]) and diabetes (the Danish Adult Diabetes Registry [DADR]). These registries hold data on disease-specific performance measures of care and several prognostic factors (15–18). An expert board representing national scientific societies and professional organizations followed a structured process to develop these performance measures on the basis of recommendations from national clinical guidelines with the highest strength of evidence. The DSR documents the following areas: diagnostic evaluation; antipsychotic treatment, including side effects; screening for cardiovascular risk factors, including, for example, glycated hemoglobin (HbA1c); family intervention; psychoeducation; suicide risk assessment; and postdischarge care. Referral of patients with schizophrenia who have increased levels of HbA1c to GPs or to specialized clinics varies. The DADR covers domains of cardiometabolic control and screening for complications. All data are prospectively collected on the basis of documentation in medical records by use of standardized registration forms with detailed instructions. The registration form is completed for all inpatients with schizophrenia at discharge from psychiatric hospitals and once a year for patients with schizophrenia followed at hospital outpatient clinics. For individuals with diabetes, quality-of-care data are recorded annually at all hospital outpatient clinics; similar diabetes care data are collected from GPs; however, completeness of data collection remains low.

The registries include records for 93% of all hospital inpatients, 92% of all hospital outpatients with schizophrenia, and approximately 90% of all hospital outpatients with diabetes in the Danish health care system (17,18). Almost all patients with schizophrenia who have been in contact with the secondary health care system can thus be identified from the DSR since its initiation in 2004, and most individuals with diabetes treated at hospital outpatient clinics can be identified from the DADR since 2005.

The PCRR has maintained a systematic collection of all psychiatric diagnoses and contacts, including dates of each admission to and discharge from Danish psychiatric hospitals, since 1969 and the start and end dates of all hospital outpatient and emergency room contacts since 1995 (19–21).

Patient-, provider-, and system-specific factors were examined as potential predictors of the quality of diabetes care among individuals with diabetes and schizophrenia. Drawn from the DADR, DSR, and PCRR, the patient-specific predictors included age, sex, smoking, alcohol or drug abuse (illegal drugs, benzodiazepines, or central stimulants), duration of schizophrenia at the time of the hospital outpatient contact for diabetes, and score on the Global Assessment of Functioning (GAF), ranging from 1 to 100, to evaluate the overall psychosocial functioning of individuals with schizophrenia (23,24).

The provider-specific predictor included the quality of schizophrenia care preceding the diabetes contact, because inadequate quality of schizophrenia care may be associated with a subsequent deficient quality of diabetes care. Table 1 lists the 12 assessed process performance measures of care, collected from the DSR, for hospital inpatients and outpatients with schizophrenia, including incident patients, defined as individuals who were diagnosed as having schizophrenia within the past year (17). The quality of schizophrenia care was assessed overall by dividing the number of performance measures received by the patient with the number of relevant measures for each individual.

Collected from the DADR, system-specific predictors included contact volume, which was defined as the average number of contacts in each hospital outpatient diabetes clinic per year from 2005 to 2013. The contact volume was divided into four quartiles; low (quartile 1, ≤519 diabetes contacts per year), medium (quartile 2, >519–895), high (quartile 3, >895–1,620), and very high (quartile 4, >1,620).

With data from the DADR, the quality of diabetes care was assessed with 11 process performance measures of care relevant to hospital outpatients with diabetes (18) (Table 2). Furthermore, we summarized the quality of diabetes care overall by dividing the number of performance measures of care received by the patient with the number of relevant measures for each individual.

Binary regression was used to examine the association between schizophrenia and the quality of diabetes care by estimating the relative risk (RR) of receiving the individual process performance measures of diabetes care and the overall quality of care among individuals with and without schizophrenia. A high quality of diabetes care was defined by using a pragmatic cut point as having received ≥80% of the relevant measures. To assess the robustness of our findings, we also repeated the analysis by using alternative thresholds ranging from 60% to 90%. The analyses were stratified according to sex, age, and HbA1c level.

Binary regression was used to elucidate the effect of patient-, provider-, and system-specific predictors on quality of diabetes care among individuals with diabetes and schizophrenia. The potential predictors included sex, age, smoking, substance abuse, GAF score, duration of schizophrenia, quality of schizophrenia care, and clinic contact volume. A high quality of schizophrenia care was defined as having received ≥80% of the relevant measures. This analysis was repeated with different cut points of 70% and 90% to evaluate the strength of the results. The adjusted analysis adjusted for predictors that were significantly associated with the outcome of interest in the unadjusted analysis. Clustering of individuals within hospital outpatient diabetes clinics was taken into account in all analyses by correcting the 95% confidence intervals (CIs) for robust estimates of the variance. A two-sided p value ≤.05 was considered to be significant. Stata, version 11.2 special edition, was used for all analyses.

The strengths of the study include the nationwide population-based design, a large sample, and detailed information about the quality of diabetes care. Nevertheless, the data in the DSR and DADR are collected in routine clinical settings by various clinicians; thus variations by practice and errors may occur. However, thorough efforts are made to ensure data uniformity and accuracy by providing detailed instructions for the data collection in standardized registration forms, with explicit data definitions. In addition, regular multidisciplinary structured audits are conducted locally, regionally, and nationally to critically assess data validity and provide continuous feedback to hospitals. To ensure high validity, data collection for the DSR and DADR focuses on a limited set of variables. Organizations are not required to maintain extensive data sets for reporting; such data sets may include incomplete and poor-quality data. Because of the limited data, however, unmeasured factors may have influenced the quality of diabetes care, including, for example, measures of disease severity other than the GAF score and racial-ethnic background, although the Danish population is in general considered to be homogeneous.

Confounding was of minor concern because the included process performance measures were considered relevant for all included individuals independent of psychiatric diagnosis, patient characteristics, and the treating hospital clinic.

This study included only hospital outpatients diagnosed as having diabetes and being treated for diabetes. The impact of schizophrenia on diabetes care may thus be considerably larger than reflected by our findings because individuals with diabetes and schizophrenia are commonly undiagnosed, not in treatment, or treated only by GPs.

The diabetes performance measures used in our study are similar to those used elsewhere, including the HEDIS measures in the United States (9–12). However, none of the prior studies were based on a nationwide population, and variation in the examined psychiatric disorder makes direct comparison difficult. Also, our results are from a system that provides universal health care, and they may not be generalizable to other health services, such as the U.S. system, which indicates the need for further studies of the quality of diabetes care among patients with schizophrenia in various settings. The limited number of studies of the association between mental illness and possible predictors of diabetes care have methodological inconsistencies (10,11). Previous U.S. studies reported that patient-specific (gender, age, race-ethnicity, and number of general medical comorbidities), provider-specific (primary care workforce), and state-specific (reimbursement rates) factors predicted the quality of care (10,11). Financial incentives may, nonetheless, further complicate comparison of results with findings from a system with universal coverage. To our knowledge, only studies in cardiovascular care have assessed the association between mental illness and the organizational structure of a health care system as a potential predictor of quality of care (25–27). U.S. studies reported that patients with mental illness were more likely than those without mental illness to be admitted to low-quality hospitals and treated by low-quality cardiac surgeons for their cardiovascular comorbidities (25–27).

This study demonstrated that the quality disparities experienced by individuals with diabetes and schizophrenia are a nationwide problem, even in a country with free access to care. Despite the younger age of individuals with diabetes and schizophrenia, their general medical health status was worse than that of individuals with diabetes alone, and those with schizophrenia were more likely to demonstrate unfavorable lifestyle behaviors, including smoking. These findings indicate possible suboptimal prophylactic medical services. Even though the sample with diabetes and schizophrenia had exacerbated general medical problems, our results indicate that they were less likely than those with diabetes alone to receive high-quality diabetes care and several individual process performance measures, including treatment with antihypertensive drugs, blood pressure monitoring, screening for albuminuria, and eye and foot examination. In this context, the relatively long intervals between diabetes follow-up checks may constitute a particular challenge in maintaining contact and providing sufficient treatment. Moreover, the mental disorder itself may affect medication adherence and awareness of diabetes complications, including reduced sight and incipient foot ulcers. Cognitive and communicative limitations may prevent this vulnerable population from seeking and receiving care.

However, it must be acknowledged that the observed differences in diabetes care were modest, which may indicate that outpatient clinics are capable of accommodating individuals with diabetes and schizophrenia. Outpatient clinics may primarily treat patients who have mild cases of schizophrenia and who are more likely to attend and receive diabetes checks. The universal health care system and the establishment of the DADR that ensures guideline-recommended care for individuals with diabetes, supported by regular audits, should also be taken into consideration when interpreting the results. The remaining individual process performance measures, including glycemic monitoring, antidiabetic medication, cholesterol monitoring, lipid-lowering medication and eye examination at least once every fourth year, were equally distributed among individuals with and without schizophrenia.

We observed that drug abuse and contact volume had the clearest association with the quality of diabetes care. Individuals with schizophrenia and documented drug abuse were less likely than those without documented drug abuse to receive a foot examination, and clinics with very high contact volume were more likely than those with low contact volume to provide high-quality diabetes care, including treatment with ACE/ATII inhibitors. Individuals with diabetes and schizophrenia and concomitant drug abuse may have difficulty attending clinics for follow-up checks. Clinics with very high contact volume may have better resources, more specialized treatments, and personnel who have greater clinical experience with psychiatric patients.

We can only speculate about the mechanisms underlying the observed deficiencies in diabetes care and predictors of such deficiencies. For individuals with diabetes and schizophrenia, navigating between the psychiatric and general medical care systems may constitute a particular challenge. Physician barriers may include minimal experience with psychiatric patients and discomfort with or stigmatizing attitudes toward these patients. In addition, system factors, such as variations in resources by clinic and region, lack of coordination between systems, and time constraints because of the need to attend to patients’ comorbid conditions, may underlie disparities. A further intermediary factor may be disengagement from treatment. Individuals with diabetes and schizophrenia may find the treatment unsuitable to their needs or may experience difficulties in their relationship with the treating physician and may thus disengage from care (28–30).