Seasonal Variations in the Achievement of Guideline Targets for HbA1c, Blood Pressure, and Cholesterol Among Patients With Type 2 Diabetes: A Nationwide Population-Based Study (ABC Study: JDDM49)

OBJECTIVE Precise monthly achievement rates for reaching guideline targets for HbA1c, blood pressure (BP), and lipid levels remain unknown. We evaluated achievement rates on a monthly basis in persons with type 2 diabetes mellitus (T2DM) and explored related factors. RESEARCH DESIGN AND METHODS This retrospective study initially analyzed data on 104,601 persons with T2DM throughout Japan. Patients whose HbA1c, BP, and LDL cholesterol were measured ≥12 times during a 24-month period were included. We evaluated monthly achievement rates. Achieved targets were defined as HbA1c <7%, BP <130/80 mmHg, and LDL cholesterol <100 mg/dL. Achievement of all targets was expressed as the “all ABC achievement.” RESULTS A total of 4,678 patients were analyzed. The achievement rates of all ABC, HbA1c, BP, and LDL cholesterol were lowest in winter, with those for systolic BP (SBP) being particularly low (all ABC, summer 15.6%, winter 9.6%; HbA1c, 53.1%, 48.9%; SBP, 56.6%, 40.9%; LDL cholesterol, 50.8%, 47.2%). In winter, age ≥65 years (odds ratio 0.47 [95% CI 0.34–0.63]) was independently related to decreased achievement rates for SBP, BMI ≥25 kg/m2 (BMI 25–30 kg/m2, 0.45 [0.29–0.70]; BMI ≥30 kg/m2, 0.35 [0.22–0.57]), and diabetes duration ≥10 years (0.53 [0.37–0.76]) were independently related to lower achievement rates for HbA1c. Insulin use and sulfonylurea use were independently associated with the decreased all ABC achievement rates in both summer and winter. CONCLUSIONS The all ABC achievement rate for guideline targets changed on a monthly basis. Seasonal variations in the all ABC achievement rate should be considered when managing T2DM in ordinary clinical practices.