Case-control study of 10 years of comprehensive diabetes care.

OBJECTIVE: To describe the long-term clinical impact of a comprehensive management program instituted throughout a health system for members with diabetes mellitus.
DESIGN: 10 year case-control evaluation.
SETTING: Kaiser Permanente Northwest, Portland, OR. PARTICIPANTS: Members of the health maintenance organization between 1987 and 1996; members with diabetes were compared with equal numbers of members without diabetes. The number of participants with diabetes ranged from 5331 in 1987 to 13,099 in 1996. MAIN OUTCOME MEASURES: Number in diabetes register, mortality, change in comorbidity, rates of uptake of preventive health measures, use of pharmaceuticals, levels of risk factors, hospital days per thousand per year, emergency room visits per thousand per year.
RESULTS: The prevalence of diabetes identified in this population rose from 2.54% (7,895/310,819) in 1987 to 3.66% (14,741/402,754) in 1996, and the mean (SEM) age of members at the time of diagnosis fell slightly from 62.9 (+/- 0.21) years to 62.0 (+/- 0.13) years (P < 0.05). By 1996, 10,885 of the 13,099 (83% +/- 0.3%) of members with diabetes had an annual laboratory test to assess glycemic control, the annual screening rate for retinopathy was 67.6% (+/- 0.4%), the rate of uptake of influenza immunizations was 60.2% (7,886/13,099) and the screening rate for nephropathy was 43% (5,698/13,099) (+/- 0.49%). The use of home glucose testing increased from 32.4% (1721/5331) of members with diabetes to 53.0% (6,942/12,099); the use of lipid lowering drugs increased from 3.5% (187/55,331) to 19.8% (2,594/13,099). The use of angiotensin converting enzyme inhibitors increased from 8.5% to 34.8% of members with diabetes. Mean blood pressure decreased from 144/82 mm Hg (+/- 0.8/0.4) to 138/79 mm Hg (+/- 0.3/0.15), and mean total cholesterol concentrations dropped from 243 mg/dL (+/- 4.2) to 215 mg/dL (+/- 0.6). By 1996, 56.4% (7,388/1,3099) (+/- 0.5%) of members on the diabetes register had good to excellent glycemic control (HbA1c < 8%). Mortality decreased from 4.8% (256/5331) (+/- 0.3%) to 3.6% (472/13,099) (+/- 0.2%) among members with diabetes, this was a more rapid decrease than was observed among those without diabetes (P < 0.01). The annual ratio of visits to the emergency room by members with diabetes to members without fell from 2.5 to 1.8, and the ratio for the number of days spent in acute care in the hospital dropped from 3.6 to 2.5.
CONCLUSIONS: This centrally organized program based in a primary care setting and utilizing a register of patients with diabetes was associated with substantial improvements in the process and outcomes of care in a large population of health maintenance organization members with diabetes.