ORIGINAL ARTICLE

Subdural hematoma in diabetic patients I.-K. Wanga,b,c, H.-J. Chend, Y.-K. Chenge,*, Y.-Y. Wuf, S.-Y. Linb, C.-Y. Choub, C.-T. Changb, T.-H. Yeng,h, F.-R. Chuangi, F.-C. Sunga,d,* and C. Y. Hsua,j Graduate Institute of Clinical Medical Science, China Medical University College of Medicine, Taichung; bDivision of Nephrology, China Medical University Hospital, Taichung; cDepartment of Internal Medicine, China Medical University College of Medicine, Taichung; dManagement Office for Health Data, China Medical University Hospital, Taichung; eDivision of Neurosurgery, China Medical University Hospital, Taichung; fDepartment of Medical Laboratory Science and Biotechnology, China Medical University, Taichung; gDivision of Nephrology, Chang Gung Memorial Hospital, Taipei; hChang Gung University College of Medicine, Taoyuan; i Division of Nephrology, Kaohsiung Chang Gung Memorial Hospital Medical Center, Chang Gung University College of Medicine, Kaohsiung; and jDepartment of Neurology, China Medical University Hospital, Taichung, Taiwan

Keywords:

diabetes mellitus, retrospective cohort study, subdural hematoma Received 24 March 2014 Accepted 23 June 2014 European Journal of Neurology 2015, 22: 99–105 doi:10.1111/ene.12538

Background and purpose: Subdural hematoma (SDH) is associated with a high mortality rate. However, the risk of SDH in diabetic patients has not been well studied. The aim of the study was to examine the risk of SDH in incident diabetic patients. Methods: From a universal insurance claims database of Taiwan, a cohort of 28 045 incident diabetic patients from 2000 to 2005 and a control cohort of 56 090 subjects without diabetes were identified. The incidence and hazard ratio of SDH were measured by the end of 2010. Results: The mean follow-up years were 7.24 years in the diabetes cohort and 7.44 years in the non-diabetes cohort. The incidence of SDH was 1.57-fold higher in the diabetes cohort than in the non-diabetes cohort (2.04 vs. 1.30 per 1000 person-years), with an adjusted hazard ratio of 1.63 [95% confidence interval (CI) 1.43–1.85]. The stratified data showed that adjusted hazard ratios were 1.51 (95% CI 1.28–1.77) for traumatic SDH and 1.89 (95% CI 1.52– 2.36) for non-traumatic SDH. The 30-day mortality rate for those who developed SDH in the diabetes cohort was 8.94%. Conclusions: This study demonstrates that incident diabetic patients are at higher risk of SDH than individuals without diabetes. Proper intervention for diabetic patients is necessary for preventing the devastating disorder.

Introduction Subdural hematoma (SDH) is the most common severe traumatic brain injury and is associated with a high mortality rate [1,2]. SDH may be of venous or arterial origin [3]. Most frequently, the hematoma results from tearing of a bridging vein between the cerebral cortex and a draining venous sinus [4]. SDH damages delicate brain tissue by increasing intracranial Correspondence: F.-C. Sung, Graduate Institute of Clinical Medical Science, China Medical University College of Medicine, 91 Hsueh Shih Road, Taichung 404, Taiwan (tel.: 886 4 2205 2121 ext 7520; fax: 886 4 2233 9216; e-mail: [email protected]). *These authors contributed equally to this study. Statistical analysis by Hsuan-Ju Chen, MS.

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pressure and shifting brain structures. The clinical manifestation of SDH can be classified into acute, subacute and chronic. Patients with acute SDH often have a major trauma, most commonly caused by motor vehicle crashes in younger patients and by falls in elderly patients [4]. In contrast, chronic SDH often occurs in elderly patients after a trivial injury or fall without accompanying injury to the underlying brain [5]. Thirty percent to 50% of patients with chronic SDH do not have a history of trauma [6]. Head injury (direct trauma) is an important cause of SDH [7]. Other risk factors include fall, old age, reduced cognitive function, use of anticoagulants or antiplatelet drugs, alcohol use, epilepsy, bleeding tendency, low cerebrospinal fluid pressure and renal

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dialysis [6,8]. Diabetes mellitus (DM) is a global serious and growing health problem with high morbidity and mortality [9]. DM and aging are known risk factors of falls [10]. A recent meta-analysis reports that individuals with DM have 12%–19% increased risk of motor vehicle accident compared with individuals without DM [11]. However, no study has investigated whether DM patients are also at higher risk of SDH. This study was to compare the risk of SDH between incident DM patients and non-DM controls using a population-based universal insurance claims database from Taiwan.

Comorbidities

Comorbidities potentially associated with SDH were also identified, including coronary artery disease (CAD) (ICD-9-CM code 410 413, 414.01 414.05, 418 and 414.9), congestive heart failure (CHF) (ICD-9-CM code 428, 398.91 and 402.x1), stroke (ICD-9-CM code 430–438), hyperlipidemia (ICD-9CM code 272), atrial fibrillation (AF) (ICD-9-CM code 427.31), hypertension (ICD-9-CM code 401 405), chronic kidney disease (CKD) (ICD-9-CM code 580–589) and dementia (ICD-9-CM code 290.0, 290.1, 290.2, 290.3, 290.4, 294.1 and 331.0).

Methods Primary outcome Data sources

The Taiwanese government launched the National Health Insurance program in March 1995, covering approximately 99% of the 23.74 million people by the end of 2009. The National Health Insurance Research Database (NHIRD) containing all claim data from 1996 to 2010 for 1 000 000 randomly selected insured people was obtained from the authority for this study. This data set provided information on registry data sets for beneficiaries including all records of outpatient visits and hospitalization, and prescribed drugs. All subjects’ identifications for linking files have been scrambled and replaced with surrogate identification numbers to protect privacy. The International Classification of Disease, 9th Revision, Clinical Modification (ICD-9-CM) was used to identify individual health status [12]. This study was approved by the Institutional Review Board of China Medical University. Study subjects

After excluding patients with diagnosed diabetes from 1996 to 1999, 28 182 patients with newly diagnosed diabetes (ICD-9-CM code 250.xx) in 2000– 2005 were identified from the records of outpatient visits and hospitalizations. Subjects with SDH before the index date (n = 127) and those with incomplete age or sex information (n = 10) were excluded from this study. The remaining 28 045 patients with newly diagnosed diabetes were included in the DM cohort. The diagnosis year of diabetes was designated as the index year for the estimation of follow-up years. For each DM subject, two insured people without a history of diabetes and SDH as the non-DM cohort, frequency matched by age (per 5 years), sex and the index year, were randomly selected.

Each subject was followed to evaluate the occurrence of SDH, including non-traumatic (ICD-9 code 432.1) and traumatic types (ICD-9-CM codes 852.2–852.3), until 31 December 2010, or was censored because of loss to follow-up, death or withdrawal from the insurance program. Furthermore, 30-day mortality was calculated using death records or withdrawal records in this database. Statistical analysis

Data analysis first estimated the annual age-standardized incidence rate of SDH for the prevalent diabetic patients from 2000 to 2010, based on the Taiwanese population in 1998. Distributions of age, sex and comorbidities were compared between the DM and nonDM cohorts and differences were examined using the chi-squared test for categorical variables and the t test for continuous variables. The Kaplan Meier estimation method was used to depict the cumulative incidence curves of SDH for the two cohorts and the difference was examined with the log-rank test. Cox proportional hazards models were used to estimate hazard ratios (HRs) of SDH for the DM cohort compared with the non-DM cohort controlling for the other variables in the model. Moreover, logistic regression analysis was used to measure the odds ratio (OR) of 30-day mortality of SDH in the DM cohort compared with the non-DM cohort. All analyses were conducted using SAS version 9.3 (SAS Institute Inc., Cary, NC, USA). The two-sided level of significance was set at 0.05.

Results Figure 1 shows the annual age-standardized incidence rate of SDH amongst patients with DM from 1998 to 2010, ranging from 2.61 to 3.55 per 1000 person-years

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Figure 1 Annual age-standardized incidence rate (per 1000 person-years) of subdural hematoma in patients with diabetes from 2000 to 2010.

(P for trend 0.246). The baseline demographic factors and comorbidities status in the DM cohort and the non-DM cohort are shown in Table 1. The distribution of age and gender were similar in both cohorts. Compared with the non-DM cohort, the DM cohort had higher rates of CAD (13.5% vs. 9.18%), CHF (5.29% vs. 3.36%), stroke (3.83% vs. 2.93%), hyperlipidemia (25.75% vs. 14.70%), AF (1.33% vs. 0.97%), hypertension (30.46% vs. 20.21%) and CKD (8.47% vs. 6.14%). Table 1 Baseline demographic characteristics and comorbidities of study subjects by diabetes status Control N = 56 090 Variable Gender Female Male Age, years

Subdural hematoma in diabetic patients.

Subdural hematoma (SDH) is associated with a high mortality rate. However, the risk of SDH in diabetic patients has not been well studied. The aim of ...
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