Differences in the Clinical Recognition of Depression in Diabetes Patients: The Diabetes Study of Northern California (DISTANCE)
Published Online: May 23, 2013
Darrell L. Hudson, PhD, MPH; Andrew J. Karter, PhD; Alicia Fernandez, MD; Melissa Parker, MS; Alyce S. Adams, PhD; Dean Schillinger, MD; Howard H. Moffet, MPH; Jufen Zhou, MS; and Nancy E. Adler, PhD
Depression is one of the most common and costly mental disorders among primary care patients in the United States.1-7 Depression is even more common among people with diabetes, 8-14 among whom it is associated with less adequate self-care (eg, poorer diet, physical inactivity, medication nonadherence, and poorer glycemic control) and poorer quality of life.15-20 Comorbid depression and diabetes has also been linked to increased risk of mortality and cognitive decline.21 Findings from the TRIAD study involving 8790 adults with diabetes enrolled in 10 managed care health plans in 7 states indicate that depressed patients achieve poorer diabetes control compared with patients who were not depressed.17,18 Depression is treated less aggressively in patients with multiple comorbidities22 and among patients with diabetes, depression is often undertreated, particularly in racial/ethnic minority groups.23
Compared with whites, US racial/ethnic minority groups have a greater prevalence of diabetes,24,25 have greater concerns about medication use,26 are more likely to have poorly controlled diabetes,18,27 and experience greater incidence of some of the major complications related to diabetes.26,28 These groups may also receive less adequate treatment for comorbid depression. Depression is underdiagnosed in general29-31 and may be even more so in some racial/ethnic minority groups.1,32,33 While findings from psychiatric epidemiologic studies indicate that rates of depression diagnosis for racial/ethnic minorities are generally lower than those for whites, members of racial/ethnic minority groups diagnosed with clinical depression report a greater burden of depressive symptoms and rate their depression as more severe and disabling than for whites.7,34 Higher rates of depressive symptoms among racial/ethnic minorities despite lower rates of diagnoses may indicate disparities in the rate of clinical recognition of depression.35,36
Randomized controlled trials investigating the efficacy of different depression treatment modalities suggest that reductions in the recurrence of depression may lead to improvements in diabetes-related outcomes such as hemoglobin A1C,26,37 and a recent trial of patient-centered management of depression and chronic disease showed significantly improved control of medical disease and depression, suggesting the utility of depression treatment when tailoring care.38
Despite the well-documented clinical importance of depression for patients with diabetes and epidemiologic evidence of racial/ethnic disparities in diabetes prevalence, diabetes control, and outcomes, there is relatively little research regarding racial/ethnic disparities in the recognition and care of depression among multi-ethnic populations with diabetes in usual care settings. We evaluated whether there were significant racial/ethnic differences in the likelihood that patients with diabetes who self-reported significant depressive symptoms would be diagnosed or treated for depression during a 12 month follow-up. The current study is based on a sample drawn from a single integrated healthcare delivery system, which may reduce confounding by access to care.
Study participants were drawn from the Diabetes Study of Northern California (DISTANCE), a follow-up study among members of the Kaiser Permanente Northern California Diabetes Registry conducted in 2005-2006. Kaiser Permanente, an integrated, non-profit, group-practice healthcare delivery organization, provides comprehensive medical services to over 3 million members in Northern California, more than 25% of the region’s population. Care is provided by more than 7000 providers at 19 hospitals and 152 medical offices. Kaiser Permanente members are predominantly employed or retired individuals and closely approximate the general population of the region ethnically and socioeconomically except for the extreme tails of the income distribution.
DISTANCE was designed to assess the association of patient, provider, and health system factors with health outcomes among patients with diabetes from 5 racial/ethnic groups. A randomly selected, ethnically stratified sample of members with diabetes receiving care from Kaiser Permanente Northern California (“Kaiser Permanente”) was invited in 2005 to 2006 to complete the survey. Of these, 20,188 patients (62% response rate among eligible members) completed surveys: 3420 African Americans (16.9%), 2312 Asians (excluding Filipinos) (11.4%), 4602 whites (22.8%), 2404 Filipinos (11.9% [we examined Filipinos separately from the broader Asian racial/ethnic group because Filipinos had a significantly different sociodemographic profile compared with the Asian group. While the DISTANCE sample did include other Pacific Islander groups, the numbers were substantially lower, so they were combined into 1 category which also included Native Americans, Eskimo, multiracial, and other/unknown]), 3717 Latinos (18.4%), 2222 multiracial (11.0%), and 1511 other (7.5%). Demographic, clinical, behavioral, and census data were available for all invited participants. No response bias was detected when comparing, among responders versus non-responders, the associations of poor glycemic control (A1C >9%) with race (P = 0.55); subsequent assessments of selection bias also failed to detect response biases.39
The DISTANCE survey took an average of 45 to 60 minutes to complete and included 4 modes of administration: 1) a computer-assisted telephone interview (CATI) administered by a third party, 2) a password-enabled, Internet-accessible survey (“web survey”) maintained on a secure server at the Kaiser Division of Research, 3) a self-administered, written survey, or 4) a short version of the written survey (the short written version was abridged and contained 40 questions). Offering the survey by oral interview in multiple languages was intended to mitigate the language and/or literacy barriers. The written and web surveys were in English only, but the CATI was available in English, Spanish, Cantonese, Mandarin, and Tagalog, using certified translations of an English script. The content of each survey mode was identical except for slight adjustments in wording as needed. Details on study recruitment procedures and sample characteristics have been published previously.40 The DISTANCE study was approved by the Institutional Review Boards of the Kaiser Foundation Research Institute and the University of California, San Francisco.
Self-Reported Depressive Symptoms
The survey included the 8-item Patient Health Questionnaire (PHQ-8), a validated screener for depression, which has been found to function similarly across different racial and ethnic groups.41 The PHQ-8 yields a valid proxy of depression diagnosis compared with other, longer clinician-administered diagnostic instruments and is widely used in clinical practices, including Kaiser Permanente.42 The PHQ-8 was used to identify current depressive symptoms. The self-report questionnaire consists of 8 out of the 9 Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, depressive disorder criteria: anhedonia, depressed mood, trouble sleeping, loss of energy, changes in appetite, trouble concentrating, and psychomotor retardation or agitation experienced over the last 2 weeks. In line with current practice, patients who scored >10 were classified as meeting criteria for depression care.41 We also examined severity of depressive symptoms using validated cut points for depression severity: moderate (PHQ score 10-14), moderatesevere (PHQ score 15-19), and severe (PHQ score >19).41
Clinically Recognized Depression
Clinically recognized depression (CRD) was our outcome of interest. Similar to previous studies, CRD was determined by the presence of a diagnosis, referral, or treatment of depression in the patient’s medical records.42,43 More explicitly, CRD was defined by the presence of any of the following within 12 months following respondents’ participation in the DISTANCE survey: 1) the diagnosis of depression in patient’s history/medical chart (International Classification of Diseases, Ninth Edition codes 296.2X, 296.3X, 296.5X, 296.8X, 296.9X, 300.4X, 309.0X, 309.1X, 309.2X, 311, 648.4X, V790, or 307.44), 2) physician referral to mental health services for depression treatment captured electronically within the Kaiser Permanente system, and/or 3) prescription written for first-line anti-depressant medications (citalopram, fluoxetine, fluvoxamine, paroxetine, sertraline, or escitalopram). We included diagnoses and treatments regardless of the clinical setting from which they were generated (eg, primary care visits or mental health visits).
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