Excess Mortality among Persons with Type 2 Diabetes

Sarah Vo, Mercer University College of Pharmacy

The prevalence of diabetes is suggested to have increased over the past two decades and is expected to affect more than 500 million adults by 2030, with most being type 2 diabetes. [1]

According to the World Health Organization, type 2 diabetes results from the body’s ineffective use of insulin.  With time, it is said that diabetes can damage the heart, blood vessels, eyes, kidneys, and nerves. [2]

According to the American Diabetes Association, diabetes remains the seventh leading cause of death in the United States in 2010.  Complications or co-morbid conditions associated with diabetes are said to include hypertension, cardiovascular disease, and dyslipidemia. [3]

Title: Excess Mortality among Persons with Type 2 Diabetes [4]
Design Retrospective; N = 2,552,852
Objective To evaluate the excess risk of death among patients with type 2 diabetes, as compared with controls, according to glycemic control and renal complications among persons who had data included in the Swedish National Diabetes Register
Study Groups Type 2 diabetics (n = 435,369) and matched controls (n = 2,117,483) in Sweden
Methods Patients and controls were followed from baseline until death or December 31, 2011, whichever came first.  For each patient, five controls were randomly selected from the general population in Sweden and matched for age, sex, and county. Data to be collected include: cause of death, age, glycated hemoglobin, and renal variables.
Duration January 1, 1998 to December 31, 2011
Primary Outcome Measure Mortality, glycated hemoglobin, and renal function
Baseline Characteristics Characteristic Patients with Type 2 Diabetes (n = 435,369) Controls (n = 2,117,483)
Age, years 65.8 ± 12.6 65.5 ± 12.5
Women, number (no.) (%) 193,340 (44.5) 953,960 (45.1)
Born in Sweden, no. (%) 360,856 (82.9) 1,855,675 (87.6)
Information from National Diabetes Register
Mean, mmol/mole of nonglycated hemoglobin 54.3 ± 4.5
Diabetes treatment, no. (%)
Diet 165,144 (37.9)
Tablets 184,002 (42.3)
Insulin 46,037 (10.6)
Insulin and tablets 40,186 (9.2)
Diabetes Duration
No. of persons with data 386,621
Mean, years 5.66 ± 7.07
Body-mass index
No. of persons with data 326,586
Mean 29.6 ± 0.95
Smoking, no. / total no. (%) 53,796/ 351,842 (15.3)
Registration in the In-Patient Register before baseline, no. (%)
Acute myocardial infarction 39,115 (9.0) 90,933 (4.3)
Coronary heart disease 68,945 (15.8) 168,292 (7.9)
Atrial fibrillation 38,164 (8.8) 117,844 (5.6)
Heart failure 30,249 (6.9) 69,844 (3.3)
Stroke 27,293 (6.3) 81,976 (3.69)
Cancer 45,907 (10.5) 209,394 (9.9)
Results Mean follow-up: type 2 diabetes = 4.6 years and controls = 4.8 years
Mortality, according to cause of death
Cause of death Patients with Type 2 Diabetes (n = 435,369) Controls (n = 2,117,483)
Any cause
No. of persons (%) 77,117 (17.7) 306,097 (14.5)
No. of deaths per 1,000 person-year (95% CI) 38.64 (38.37 – 38.91) 30.19 – 30.41)
Cardiovascular cause
No. of persons (%) 34,238 (7.9) 129,917 (6.1)
No. of deaths per 1,000 person-year (95% CI) 17.15 (16.97 – 17.34) 12.86 (12.79 – 12.93)
Age (years) Glycated hemoglobin level (%) Hazard ratio (95%, Confidence interval (CI))
Patients with type 2 diabetes
< 55 ≤ 6.9 1.92 (95% CI, 1.75 to 2.11)
≥ 75 ≤ 6.9 0.95 (95% CI, 0.94 to 0.96)
Patients with normalbuminuria
< 55 ≤ 6.9 1.60 (95% CI, 1.40 to 1.82)
65 – 74 ≤ 6.9 0.87 (95% CI, 0.84 to 0.91)
≥ 75 ≤ 6.9 0.76 (95% CI, 0.75 to 0.78)
Adverse Events Common Adverse Events: not applicable
Serious Adverse Events: not applicable
Percentage that Discontinued due to Adverse Events: not applicable
Study Author Conclusions In conclusion, the overall excess risk of death among persons with type 2 diabetes has dropped to a historically low level of approximately 15%.  However, mortality remains high in certain patient groups and remains substantially higher among patients younger than 55 years of age, as compared with controls, even among patients whose glycemic values are within the target range and who have normoalbuminuria.

One of the strengths of this study was that it included more than 90% of all the patients with type 2 diabetes in Sweden.  Unlike previous studies, this study provided information on coexisting diseases and psychosocial variables in controls.

A limitation of this study was that the prevalence of obesity, diet, and diabetes care may differ among countries.  Therefore, evaluations may not be generalized to other countries.

The excess risks of death from any causes and cardiovascular death increased with younger age, worse glycemic control, and greater severity of renal complications.

References

  1. Whiting DR,Guariguata L, Weil C, Shaw J. IDF Diabetes Atlas: global estimates of the prevalence of diabetes for 2011 and 2030. Diabetes Res Clin Pract 2011;94:311-321
  2. The World Health Organization.  http://www.who.int/mediacentre/factsheets/fs312/en/.  Updated January 2015.  Accessed November 3, 2015.
  3. Statistics About Diabetes. The American Diabetes Association.  http://www.diabetes.org/diabetes-basics/statistics/?referrer=https://www.google.com/.  Updated May 19, 2015.  Accessed November 03, 2015.
  4. Tancredi M, Rosengren A, Svensson AM, et al. Excess Mortality among Persons with Type 2 Diabetes. N Engl J Med. 2015;373(18):1720-32.
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