Hemoglobin A1c and Associated Risk Factors in Older Adults
Fasting plasma glucose (FPG) and the oral glucose tolerance test (OGTT) are considered to be appropriate tests for diagnosing pre-diabetes and/or diabetes while OGTT is also considered an appropriate test for assessing diabetes risk in patients with impaired fasting glucose (IFG). As an alternative to these methods, an International Expert Committee, including representatives of the American Diabetes Association (ADA), the International Diabetes Federation (IDF), and the European Association for the Study of Diabetes (EASD), recently recommended evaluating glycosylated hemoglobin (HbA1c), with a cut-off point of ≥ 6.5% to diagnose diabetes (the HbA1c of young, lean and healthy subjects is approximately 5.0%.) This strategy was endorsed and adopted by the ADA in 2010.
Epidemiological evidence suggests that elevated HbA1c is associated with cardiovascular and ischemic heart disease risk. Both obesity and physical inactivity are considered to play important roles in the prevention and treatment of diabetes, with the ADA recommending that people with HbA1c of 5.7–6.4% undergo moderate weight loss (7% of initial body mass), as well as increasing physical activity to at least 150 min/week of moderate activity.
Ageing is another factor that contributes to variance in HbA1c and diabetes risk. Even in nondiabetic adults with normal fasting glucose, HbA1c steadily increase with age, such that at 70+ years of age it is 5.5%, almost attaining the ADA criterion for prediabetes. It should be noted, however, that ageing is also associated with a number of risk factors common to the sedentary/obese lifestyle that are expected to be associated with elevated HbA1c levels, including increased body and abdominal fat, a more atherogenic lipid profile, diabetes, elevated inflammatory markers, decreased cardiorespiratory fitness and reduced physical activity. Any, or all, of these risk factors are expected to be associated with elevated HbA1c levels. There is, however, little information as to what extent factors such as obesity or physical inactivity in older adults modify HbA1c levels above and beyond the effect of aging, per se. This knowledge is essential for determining whether or not 1) lowering HbA1c by diet and exercise is a realistic goal for obese and inactive elderly subjects and 2), if this is indeed achievable, what should be the target levels HbA1c to attain?
The United States Department of Health and Human Services (USDHHS) established cut-off points of > 88 cm waist circumference for women, and > 102 cm waist circumference for men, combined with a body mass index (BMI) of ≥ 30 kg/m to define obesity. Similarly, the International Diabetes Federation (IDF) have recommended specific population-based cut-off points for waist circumference, with suggested values of ≥ 80 cm for European women and ≥ 94 cm for European men. Recognizing these criteria to define obesity, the aim of this study is to investigate, in older women and men, the relationships between HbA1c and other risk factors like obesity, functional fitness, lipid profile, and inflammatory status. A secondary aim of this investigation is to compare HbA1c in obese and non-obese older adults, using different cut-off points for obesity.
Background
Fasting plasma glucose (FPG) and the oral glucose tolerance test (OGTT) are considered to be appropriate tests for diagnosing pre-diabetes and/or diabetes while OGTT is also considered an appropriate test for assessing diabetes risk in patients with impaired fasting glucose (IFG). As an alternative to these methods, an International Expert Committee, including representatives of the American Diabetes Association (ADA), the International Diabetes Federation (IDF), and the European Association for the Study of Diabetes (EASD), recently recommended evaluating glycosylated hemoglobin (HbA1c), with a cut-off point of ≥ 6.5% to diagnose diabetes (the HbA1c of young, lean and healthy subjects is approximately 5.0%.) This strategy was endorsed and adopted by the ADA in 2010.
Epidemiological evidence suggests that elevated HbA1c is associated with cardiovascular and ischemic heart disease risk. Both obesity and physical inactivity are considered to play important roles in the prevention and treatment of diabetes, with the ADA recommending that people with HbA1c of 5.7–6.4% undergo moderate weight loss (7% of initial body mass), as well as increasing physical activity to at least 150 min/week of moderate activity.
Ageing is another factor that contributes to variance in HbA1c and diabetes risk. Even in nondiabetic adults with normal fasting glucose, HbA1c steadily increase with age, such that at 70+ years of age it is 5.5%, almost attaining the ADA criterion for prediabetes. It should be noted, however, that ageing is also associated with a number of risk factors common to the sedentary/obese lifestyle that are expected to be associated with elevated HbA1c levels, including increased body and abdominal fat, a more atherogenic lipid profile, diabetes, elevated inflammatory markers, decreased cardiorespiratory fitness and reduced physical activity. Any, or all, of these risk factors are expected to be associated with elevated HbA1c levels. There is, however, little information as to what extent factors such as obesity or physical inactivity in older adults modify HbA1c levels above and beyond the effect of aging, per se. This knowledge is essential for determining whether or not 1) lowering HbA1c by diet and exercise is a realistic goal for obese and inactive elderly subjects and 2), if this is indeed achievable, what should be the target levels HbA1c to attain?
The United States Department of Health and Human Services (USDHHS) established cut-off points of > 88 cm waist circumference for women, and > 102 cm waist circumference for men, combined with a body mass index (BMI) of ≥ 30 kg/m to define obesity. Similarly, the International Diabetes Federation (IDF) have recommended specific population-based cut-off points for waist circumference, with suggested values of ≥ 80 cm for European women and ≥ 94 cm for European men. Recognizing these criteria to define obesity, the aim of this study is to investigate, in older women and men, the relationships between HbA1c and other risk factors like obesity, functional fitness, lipid profile, and inflammatory status. A secondary aim of this investigation is to compare HbA1c in obese and non-obese older adults, using different cut-off points for obesity.