Department of Rheumatology, Endocrinology and Nephrology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan. Clinical Research and Medical Innovation Center, Hokkaido University Hospital, Sapporo, Japan. Third Department of Internal Medicine, Hokkaido PWFAC Obihiro-Kosei General Hospital, Obihiro, Japan. Sapporo Diabetes and Thyroid Clinic, Sapporo, Japan. Division of Diabetes and Endocrinology, Department of Medicine, Sapporo Medical Center, NTT East Corporation, Sapporo, Japan. Diabetes Center, Manda Memorial Hospital, Sapporo, Japan. Department of Internal Medicine, Jiyugaoka Medical Clinic, Obihiro, Japan. Kurihara Clinic, Sapporo, Japan. Aoki Clinic, Sapporo, Japan. Biostatistics Section, Clinical Research and Medical Innovation Center, Hokkaido University Hospital, Sapporo, Japan. Division of Diabetes and Obesity, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan.