[Epidemiological study on HbA1c level below 6.1% among community residents and follow-up study of HbA1c level - clinical significance of health examination (Japan) in the aged members from the view point of glucose metabolism - ].

AIM: This study is to investigate whether the set point of HbA1c being 5.2% or more is too strict a line to be drawn by Tokutei-kensin (Health Examination for metabolic syndrome in Japan) on people 65 years old or more from the view point of glucose metabolism.

METHODS: Samples were out-patients of the community clinic and community residents from the jurisdiction of the community clinic. (1) Epidemiological data on those who were in their 50s, 60s and 70s with HbA1c level between 5.2% or more. (2) Second study was done on those who aged 40 years or more with their initial HbA1c measured after 1995 with a result of 6.1% or less, and had been followed for more than 5 years since.

RESULTS: First study covered 54.3% and 69.3% of age groups of 60s and 70s respectively and the percentages of HbA1c between 5.2% and 6.1% were 40.9%, 36.8% respectively. HbA1c level of 40 people who met the criteria of second study were followed for 5 to 13 years. Among 29 cases of those who aged between 40 and 75, 15 cases showed an increase from 5.2% to 6.1% over an average of 9.6 years of follow up and 7 of them increased to higher than 6.5%. When limited to the age of 65 to 75, 8 of them increased from 5.2% to 6.1% and 2 of them increased to higher than 6.5%. None of the 19 cases who were more than 40 years old and had an initial HbA1c below 5.2% showed a significant elevation of HbA1c.

CONCLUSIONS: It is reported that diabetic cardiovascular complications exists in pre-dibetic stage and oral glucose tolerance test revealed high percentage of impaired glucose tolerance among HbA1c values between 5.2 and 6.1%. It has been investigated that among people aged between 65 and 74, those who had a HbA1c higher than 5.2% showed an increase of HbA1c over years when compared to those whose HbA1c below 5.2%. It was also reported that about 40% of the population of people in their 60s and 70s had a between HbA1c 5.2% and 6.1%. It is considered important that an assessment of state of arteriosclerosis and intervention of life style to people aged 65 to 74 when a value of HbA1c over 5.2% is found.