Young-onset type 2 diabetes associated with increased risk of hospitalization frequently due to mental illness

1. Patients with young-onset type 2 diabetes had higher rates of all-cause hospitalization than usual-onset diabetes. Over one-third of the total hospitalization bed-days were attributable to mental illness.

2. In a retrospective model, hospitalization rates could be reduced with improved control of modifiable risk factors.

Evidence Rating Level: 2 (Good)

Study Rundown: Type 2 diabetes diagnosed before age 40 is referred to as “young-onset type 2 diabetes” or “YOD.”  In this study, the authors explored the risk of general and cause-specific hospitalization over the lifetime of a patient with YOD.  Interestingly, over a third of the total hospital bed-days for these patients were attributable to mental illness, usually psychosis and mood disorders.  By the age of 60, the rate of all-cause hospitalization was double that of patients with usual-onset diabetes. The relative risk was also significantly higher in these patients for hospitalizations due to renal disease, diabetes, cardiovascular disease, and infection.  In a retrospective model, hospitalization rates improved with control of modifiable risk factors like hemoglobin A1C, systolic blood pressure, cholesterol, triglyceride levels, and waist circumference.

A major strength of this study was that it accessed data from a hospital system with nearly universal coverage of local patients, which allowed for standardized record keeping, minimal bias in patient selection, and almost perfect follow-up.  However, the cohort only included patients from Hong Kong and most of the diagnosis-specific results were based on a much smaller cohort, which introduced additional confounders.  For instance, these data may have been biased by the high mortality in the sickest of the patients, who were disproportionately in the YOD group. Further studies will be necessary to determine if these results are applicable outside this single hospital system.

Click to read the study, published today in Annals of Internal Medicine

Relevant Reading: Estimated morbidity and mortality in adolescents and young adults diagnosed with Type 2 diabetes mellitus

In-Depth [prospective cohort]: The authors conducted two parallel prospective cohort studies with patients with type 2 diabetes.  The “population cohort” included 422,908 patients with T2D who were admitted to the Hong Kong Hospital Authority between 2000-2014 (2.8 million-person years).  The “registry cohort” was smaller but included more detailed information, and covered 20,866 patients who enrolled in a registry between 2000 and 2014 (0.2 million person years).  In both cohorts, all-cause hospitalization rates were higher in patients with YOD across all age groups.  For YOD patients in the “registry cohort,” 36.8% of bed-days before the age of 40 were attributed to mental illness, with 55.1% related to psychotic disorders and 31.4% related to mood disorders.  This trend persisted after controlling for the increased rates of diabetes in patients taking atypical antipsychotics.  Admission rates were also significantly higher in patients with YOD than usual-onset T2D for renal diseases (rate ratio 6.7, 95%CI 4.2-10.6), cardiovascular disease (RR 2.1, 95%CI 1.8-2.5), diabetes (RR, 3.7, 95%CI 3.0-4.6), and infection (RR 1.7, 95%CI 1.4-2.1).  In order to estimate the impact of intensified risk-factor control, the authors compared the relative risk of patients who did and did not meet target criteria for certain modifiable risk factors including hemoglobin A1C, systolic blood pressure, low-density lipoprotein C, triglycerides, smoking cessation, and waist circumference.  Based on this retrospective model, modifiable risk factors reduce cumulative hospitalization days by about one-third.

Image: PD

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