The prevalence estimates for each the microvascular conditions in people with a history of diabetes were as follows: 27.7% had chronic kidney disease, 23.0% had albuminuria (4.1% macroalbuminuria), and 11.4% had retinopathy. In people without a history of diabetes, the corresponding prevalence estimates were 18.1% for chronic kidney disease, 10.4% for albuminuria (0.9% macroalbuminuria), and 2.8% for retinopathy. Demographic and clinical variables also differed substantially by diabetic status (). People with a history of diagnosed diabetes were more likely to be men and African American and have a high-school education or less and a family history of diabetes compared with people in the study sample with no history of diabetes. People with diagnosed diabetes also had poorer cardiovascular risk profiles and were less likely to be current smokers.
| Table 1Participant characteristics overall and by diabetes history |
Mean levels of the different glycemic markers differed substantially by diabetic status ( and ). The mean glycated albumin, fructosamine, 1,5-AG, HbA1c, and fasting glucose values in people without a history of diagnosed diabetes were 13.6%, 230.1 μmol/L, 17.9 μg/mL, 5.6%, and 102.7 mg/dL, respectively. In people with diabetes, the corresponding means were 17.8%, 274.3 μmol/L, 12.6 μg/mL, 6.7%, and 140.1 mg/dL, respectively. reveals substantial differences in the associations of each marker with basic demographic and clinical characteristics. In people without diabetes, glycated albumin was significantly higher and 1,5-AG was lower in people aged 65 years and older compared with people <65 years of age; fructosamine, HbA1c, and fasting glucose did not differ by age group. Whereas fructosamine and glycated albumin appeared similar by sex, men had significantly higher 1,5-AG, higher HbA1c, and higher fasting glucose. BMI was significantly associated with all markers but not in the expected direction for glycated albumin or fructosamine, which were both lower, and for 1,5-AG, which was higher, at higher BMI levels. By contrast, HbA1c and fasting glucose were both significantly higher at higher BMI levels. Levels of glycated albumin and fructosamine were also significantly higher in people who have never smoked compared with former or current smokers. HbA1c and fasting glucose were not significantly different across categories of smoking. Substantial racial differences were seen across all markers in both people with and without diabetes, with African Americans having higher levels of glycemia as indicated by each marker, although the results were not statistically significant for 1,5-AG in people with or without diabetes. Fasting glucose was higher, but not statistically significantly so, in diabetic African Americans compared with whites (P value = 0.13). In these unadjusted analyses, we observed associations between some of the glycemic markers and prevalent chronic kidney disease, albuminuria, and retinopathy, but these results were variable across the different measures of hyperglycemia ( and ).
| Table 2Mean levels of glycemic markers by demographic and clinical characteristics in participants without a history of diabetes (n = 1,323) |
| Table 3Mean levels of glycemic markers by demographic and clinical characteristics in participants with diagnosed diabetes (n = 277) |
In our adjusted logistic regression models of microvascular outcomes in the total population comparing diabetes-specific tertiles of each glycemic marker, we observed significant positive trends in the associations of each marker with albuminuria and retinopathy ( and
Supplementary Table 1), even after accounting for demographic, clinical, and lifestyle factors. The associations with chronic kidney disease were similar in magnitude and direction but not significant for all markers: glycated albumin (
P trend = 0.005), fructosamine (
P trend = 0.003), and HbA
1c (
P trend = 0.005) were significantly and positively associated with the presence of chronic kidney disease, but 1/1,5-AG (
P trend = 0.72) and fasting glucose (
P trend = 0.66) were not. After further adjustment for HbA
1c in these models (
Supplementary Fig. 1 and Supplementary Table 2), we observed significant trends in the associations of glycated albumin with retinopathy (
P trend = 0.01) and borderline significant trends for chronic kidney disease (
P trend = 0.05) and albuminuria (
P trend = 0.07). After adjustment for HbA
1c, positive trends for fructosamine also remained significant for chronic kidney disease (
P trend = 0.03) and retinopathy (
P trend = 0.02) and borderline significant for albuminuria (
P trend = 0.05). 1/1,5-AG remained significantly positively associated with albuminuria (
P trend = 0.04) but not with chronic kidney disease (
P trend = 0.63) or retinopathy (
P trend = 0.42). Overall trends for fasting glucose were not significant for any outcome after adjustment for HbA
1c (all
P trends >0.3); however, the lowest tertile of fasting glucose in people with diagnosed diabetes was significantly associated with chronic kidney disease and albuminuria. HbA
1c, by contrast, was no longer statistically significantly associated with any of these outcomes in these fully adjusted models (all
P values >0.05).