1. Department of Cardiovascular, Renal and Metabolic Medicine, Sapporo Medical University School of Medicine, Sapporo 060-8543, Japan
2. Department of Nephrology, Teine Keijinkai Hospital, Sapporo 006-8555, Japan
3. Sanwa Kagaku Kenkyusho Co., Ltd., Inabe 511-0406, Japan
4. Department of Public Health, Sapporo Medical University School of Medicine, Sapporo 060-8543, Japan
5. Department of Nursing, Division of Medical and Behavioral Subjects, Sapporo Medical University School of Health Sciences, Sapporo 060-8543, Japan
6. Japan Health Care College, Sapporo 004-0839, Japan