Table 1

General characteristics and retinal and skin measures for the retinal study population according to glucose metabolism status

CharacteristicsNGM (n = 1,040)Prediabetes (n = 276)T2D (n = 475)
Age (years)58.0 ± 8.261.5 ± 7.262.9 ± 7.6
Women596 (57.3)130 (47.1)147 (30.9)
Diabetes duration (years)*6.0 (3.0–12.0)
Diabetes medication use
 Any type359 (75.6)
 Insulin86 (18.1)
 Oral glucose-lowering medication338 (71.2)
BMI (kg/m2)25.5 ± 3.427.5 ± 4.029.5 ± 4.5
Waist circumference (cm)
 Men96.3 ± 9.1101.6 ± 9.4106.7 ± 11.6
 Women85.6 ± 9.792.7 ± 12.1100.9 ± 13.6
Smoking
 Never/former/current, n409/502/11675/161/33136/264/62
 Never/former/current, %39.8/48.9/11.327.9/59.9/12.329.4/57.1/13.4
History of cardiovascular disease116 (11.4)30 (11.2)118 (25.8)
eGFR (mL/min/1.73 m2)89.9 ± 13.087.2 ± 14.085.3 ± 17.2
eGFR <60 mL/min/1.73 m218 (1.7)10 (3.6)45 (9.5)
(Micro)albuminuria47 (4.6)15 (5.4)77 (16.2)
Retinopathy1 (0.1)1 (0.4)18 (3.9)
Composite indices of potential mediators
Markers of hyperglycemia
 HbA1c (%)5.4 ± 0.45.7 ± 0.46.8 ± 0.9
 HbA1c (mmol/mol)35.8 ± 3.738.4 ± 4.550.6 ± 9.9
 Fasting glucose (mmol/L)5.2 ± 0.45.9 ± 0.67.7 ± 1.7
 2-h postload glucose (mmol/L)§5.4 ± 1.18.2 ± 1.714.2 ± 3.9
 Skin autofluorescence (AU)2.3 ± 0.52.4 ± 0.52.6 ± 0.6
Markers of blood pressure
 Ambulatory 24-h SBP (mmHg)117.3 ± 11.1120.1 ± 11.9122.4 ± 11.7
 Ambulatory 24-h DBP (mmHg)73.6 ± 7.274.5 ± 7.373.0 ± 7.0
 Antihypertensive medication use226 (21.7)113 (40.9)333 (70.1)
Markers of lipid profile
 Total-to-HDL cholesterol ratio3.5 ± 1.13.9 ± 1.33.7 ± 1.1
 LDL cholesterol (mmol/L)3.3 ± 0.93.3 ± 1.12.4 ± 0.9
 Total cholesterol (mmol/L)5.6 ± 1.05.5 ± 1.24.4 ± 1.1
 HDL cholesterol (mmol/L)1.7 ± 0.51.5 ± 0.41.3 ± 0.4
 Triglycerides (mmol/L)1.2 ± 0.61.6 ± 1.01.8 ± 0.9
 Lipid-modifying medication use178 (17.1)93 (33.7)350 (73.7)
Markers of insulin resistance
 HOMA2-IRInsulin (AU)1.3 ± 0.71.9 ± 1.12.4 ± 1.4
 HOMA2-IRC-peptide (AU)1.3 ± 0.51.7 ± 0.72.1 ± 0.9
Markers of low-grade inflammation
 hs-CRP (mg/L)1.1 (0.6–2.2)1.8 (0.8–3.5)1.5 (0.7–3.3)
 Serum amyloid A (mg/L)3.0 (1.9–5.0)3.6 (2.3–5.7)3.5 (2.2–6.0)
 Soluble ICAM-1 (ng/mL)338.6 ± 80.2365.8 ± 103.2383.8 ± 115.9
 Interleukin-6 (pg/mL)0.5 (0.4–0.8)0.6 (0.4–0.9)0.8 (0.6–1.1)
 Interleukin-8 (pg/mL)3.7 (3.0–4.6)4.3 (3.3–5.3)4.8 (4.0–6.1)
 Tumor necrosis factor-α (pg/mL)2.1 (1.8–2.4)2.2 (1.9–2.6)2.5 (2.1–2.9)
Markers of arterial stiffness
 Carotid-femoral pulse wave velocity (m/s)8.4 ± 1.79.2 ± 2.19.9 ± 2.3
 Carotid distensibility coefficient (103/kPa)15.1 ± 5.213.7 ± 4.813.3 ± 4.9
Microvascular outcomes
Baseline arteriolar diameter (MU)115.3 ± 15.3114.8 ± 15.9116.0 ± 15.9
Arteriolar average dilation (%)
 Mean ± SD3.4 ± 2.83.1 ± 2.82.4 ± 2.7
 Median [interquartile range]3.0 (1.1–5.3)2.8 (0.8–5.0)1.6 (0.4–3.9)
Baseline skin blood flow (PU)10.8 ± 6.411.7 ± 7.211.0 ± 5.7
Skin hyperemic response (%)
 Mean ± SD1,252.6 ± 813.41,107.4 ± 710.8941.7 ± 701.1
 Median [interquartile range]1,104.0 (668.7–1,656.9)1,006.9 (604.9–1,536.9)821.2 (479.0–1,209.8)
  • Data are reported as mean ± SD, median [interquartile range], or number (%) as appropriate. AU, arbitrary units; DBP, diastolic blood pressure; eGFR, estimated glomerular filtration rate; HOMA2-IR, HOMA of insulin resistance; ICAM, intercellular adhesion molecule; MU, measurement units; PU, perfusion units; SBP, systolic blood pressure.

  • * Available in 313 individuals with type 2 diabetes.

  • (Micro)albuminuria was defined as a urinary albumin excretion of >30 mg per 24 h.

  • Indicates that the individual marker is part of the corresponding composite index.

  • § Available in 389 individuals with T2D, as the oral glucose tolerance test was not performed in individuals who were on insulin treatment.

  • Heat-induced skin hyperemia measures were available in a different subset of n = 1,281.