Temporal changes in mean HbA1c in a general population: comparisons between 1997 and 2002, the Japan National Diabetes Surveys

Abstract

This study examines the change in mean hemoglobin A1c (HbA1c) from 1997 to 2002 and evaluates factors associated with HbA1c, by analyzing two points cross-sectional data from the Japan National Diabetes Surveys. The study included 2,095 men and 3,340 women in 1997, and 1,960 men and 3,115 women in 2002 without a previous history of diabetes. Differences between the two surveys were compared. A multivariable linear regression model was used to identify factors related to HbA1c. The mean HbA1c was 0.15 % higher in 2002 than 1997 in men (5.29 to 5.44 %, P < 0.001) and 0.14 % higher in women without a previous history of diabetes (5.33 to 5.47 %, P < 0.001). In men, mean BMI increased (23.1 to 23.7 kg/m2, P < 0.001), SBP decreased (137 to 133 mmHg, P = 0.006), and the proportion of current smokers (53 to 45 %, P < 0.001) and current drinkers decreased (52 to 48 %, P = 0.047). In women, mean BMI showed no change and SBP decreased (131 to 127 mmHg, P = 0.020). Age, BMI, current non-drinker, and the time trend (5 years from 1997 to 2002) were associated with HbA1c in both sexes and current smoking and daily footsteps were associated with HbA1c only in men. The mean HbA1c increased by 0.14–0.15 % in both sexes from 1997 to 2002 among Japanese people without a previous history of diabetes. The increase in HbA1c from 1997 to 2002 could partly be related to the increase of BMI in men. Such temporal changes of HbA1c should be further investigated in the national data to search for contributing factors to promote health care related to diabetes in Japan.