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Tracking of glycated hemoglobin in the original cohort of the Framingham Heart Study
J B Meigs1, D M Nathan, L A Cupples
1General Internal Medicine Unit, Massachusetts General Hospital, Boston 02114, USA.
Insights
Glycated hemoglobin A1c (HbA1c) reliably tracks blood glucose control in nondiabetic individuals over 4-6 years. This measure is valuable for epidemiological studies, showing good reliability and small changes over time.
Area of Science:
- Endocrinology
- Epidemiology
- Gerontology
Background:
- Glycated hemoglobin (HbA1c) reflects average blood glucose over 2-3 months.
- Understanding HbA1c stability is crucial for its use in long-term studies.
Purpose of the Study:
- To evaluate the tracking and reliability of HbA1c measurements in elderly, nondiabetic individuals over a 4- to 6-year period.
Main Methods:
- Utilized two HbA1c measurements from 639 elderly participants in the Framingham Heart Study (1986-1993).
- Analyzed intraclass correlation, percentage change from baseline, and factors associated with HbA1c change.
Main Results:
- Intraclass correlation of 0.59 indicated good reliability of single HbA1c measurements.
- 91% of follow-up HbA1c values were within 20% of baseline; values moved 15% closer to the mean.
- A modest, statistically significant increase in HbA1c was observed over time, influenced slightly by age, BMI, and smoking.
Conclusions:
- HbA1c is a reliable measure for categorizing glucose control in nondiabetic subjects over extended periods.
- Confirms the utility of HbA1c as a robust epidemiological tool for assessing long-term glycemic status.
Abstract:
Glycated hemoglobin measures average blood glucose over the preceding 2 to 3 months. The authors examined the tracking of the major glycated hemoglobin A1c (HbA1c), over a period of 4 to 6 years. Two HbA1c measurements were obtained between 1986 and 1993 from 639 elderly, presumptively nondiabetic members of the original cohort of the Framingham Heart Study, Framingham, Massachusetts. Mean +/- standard deviation (SD) baseline and follow-up HbA1c were 5.43% +/- 0.7 and 5.71% +/- 0.9, respectively. Intraclass correlation of 0.59 between baseline and follow-up measurements indicated good reliability of a single HbA1c measurement. Ninety-one percent of follow-up measurements were within +/- 20% of baseline value; HbA1c values tended to move 15% closer to the baseline mean over time. There was a modest tendency for HbA1c values to increase with time; the mean difference between measurements was 0.28% +/- 0.7 SD (p < 0.0001). Change in HbA1c was positively associated with age and body mass index at baseline examination, and negatively associated with cigarette smoking, even after controlling for age and body mass index. These effects were very small, however. We conclude that glycated hemoglobin reliably categorizes the glucose control of nondiabetic subjects over a period of 4 to 6 years, confirming its value as an epidemiological measure.