Insulin pump therapy has been used in patients with type 1 diabetes for 25 years (1–3). In recent years, several studies have demonstrated that continuous subcutaneous insulin infusion (CSII) is also safe and effective in adolescents and children (4–9). In the majority of studies, CSII has been shown to improve HbA1c while not changing or decreasing the risk of hypoglycemia. There is little information about the optimal treatment of older adults with type 1 diabetes (10). Risk for hypoglycemia is reported to be increased in older patients with diabetes and in those with long-standing diabetes, especially in those treated with injected insulin (11). We hypothesized that switching from multiple daily injection of insulin (MDI) to CSII in older patients with type 1 diabetes would improve metabolic control of diabetes and reduce the incidence of hypoglycemia.
Thirty-four patients aged >50 years with type 1 diabetes were selected to switch from MDI to CSII from among patients followed at the Naomi Berrie Diabetes Center at the Columbia University Medical Center in New York City. MDI regimens included insulin glargine once daily in 10 patients and NPH insulin twice daily in 24 patients; all patients were additionally treated with premeal insulin analog injections. Twelve patients had a history of retinopathy, 10 had neuropathy, and 9 had nephropathy. Four patients had undergone coronary artery bypass surgery, and one had a history of myocardial infarction. Data were obtained by chart review 12 months before and after initiation of CSII.
Glucose control, as reflected by HbA1c, was significantly improved with 1 year of CSII therapy (P < 0.05 by ANOVA). Mean HbA1c was 7.64 ± 0.19% before CSII initiation, 7.23 ± 0.20 after 6 months of pump therapy, and 7.01 ± 0.10% (a significant decline, P < 0.01) after 1 year. Rates of severe hypoglycemia were reduced in the patients when treated with CSII. In the year before CSII initiation, seven patients on MDI required emergency room treatment for hypoglycemia. One patient was treated in the emergency room for hypoglycemia in the year following CSII initiation (P < 0.05 by exact one-sided P values from McNemar’s test). Nine patients had hypoglycemic seizures in the year before pump start and one patient had a hypoglycemic seizure in the first 2 weeks after initiation of CSIII (P < 0.02). Mean BMI was 23.7 kg/m2 (range 18.5–26) before pump start and did not change significantly after 1 year of CSII. No subjects discontinued CSII and returned to MDI.
A limitation of this study is that it was not randomized. The older patients with type 1 diabetes who were treated with pump therapy were carefully selected for CSII, and those unwilling or unable to master the technological and other features of CSII were not included.
These findings suggest that insulin pump therapy leads to decreased rates of hypoglycemia while improving glucose control in selected older adults with long-standing type 1 diabetes. CSII is an important alternative to MDI in older adults with type 1 diabetes, particularly those who experience significant hypoglycemia in association with therapy with injected insulin.
