Increasing incidence of serious hypoglycemia in insulin users

Trials provide most of the data on the incidence of hypoglycemia in patients with diabetes. However, trial protocols may not reflect changes in diabetes management that occur over time. Using a retrospective cohort design, we calculated the incidence of hypoglycemia in 1,113 patients 20 to 64 years of age who used insulin monotherapy from 1993 through 1997 at Harvard Pilgrim Health Care, a health maintenance organization (HMO) in New England. Episodes included emergency department visits or hospital admissions for hypoglycemia identified through insurance claims and documented in patients' medical records. The incidence of hypoglycemia was 5.07 episodes per 100 person-years (95% CI, 4.14 to 6.00); 203 confirmed episodes occurred in 129 unique patients during 4,005 person-years of follow-up. The incidence increased by approximately 24% per year (rate ratio = 1.24; 95% CI, 1.11 to 1.38) from 1993 through 1997, perhaps reflecting physicians' and patients' efforts to intensify glucose management.