Table 1.
Population characteristics of the total population and by tertiles of sural SNAP amplitude
| Characteristic | Total (n = 2401) | High (n = 793) | Medium (n = 796) | Low (n = 812) |
|---|---|---|---|---|
| Age (years) | 59.3 (8.2) | 56.4 (8.2) | 59.4 (7.9) | 62.0 (7.5) |
| Sex (% men) | 51.1 | 41.5 | 52.6 | 58.9 |
| Education level (% high) | 39.7 | 39.2 | 42.6 | 37.3 |
| Smoking status (% current smokers) | 12.8 | 12.4 | 14.1 | 11.8 |
| Alcohol use (% high consumers) | 26.7 | 26.7 | 25.8 | 27.6 |
| Mobility limitation (% with limitation) | 2.5 | 2.1 | 2.1 | 3.3 |
| (History of) cardiovascular disease (%) | 16.1 | 12.9 | 15.7 | 19.3 |
| The metabolic syndrome (%) | 37.1 | 26.9 | 38.8 | 45.3 |
| Prediabetes (%) | 15.4 | 13.2 | 16.7 | 16.3 |
| Type 2 diabetes (%) | 25.3 | 16.8 | 24.4 | 34.5 |
| Fasting glucose (mmol/l) | 5.5 [5.0–6.3] | 5.3 [4.9–5.8] | 5.5 [5.1–6.3] | 5.8 [5.3–7.3] |
| HbA1c (mmol/mol) | 38.0 [35.0–43.0] | 37.0 [34.0–40.0] | 38.0 [35.0–43.0] | 39.5 [36.0–47.0] |
| HbA1c (%) | 5.6 [5.3–6.0] | 5.5 [5.3–5.8] | 5.6 [5.3–6.1] | 5.7 [5.4–6.5] |
| BMI (kg/m2) | 26.8 (4.3) | 26.0 (3.8) | 26.8 (4.2) | 27.5 (4.6) |
| Waist circumference (cm) | 94.9 (13.1) | 91.6 (12.1) | 95.1 (12.4) | 98.0 (13.7) |
| Systolic blood pressure (mmHg) | 134.6 (17.9) | 131.7 (17.8) | 134.9 (17.2) | 137.2 (18.2) |
| Diastolic blood pressure (mmHg) | 76.2 (9.8) | 75.9 (10.2) | 76.7 (9.6) | 76.0 (9.7) |
| HDL-cholesterol (mmol/l) | 1.5 (0.5) | 1.6 (0.5) | 1.5 (0.5) | 1.5 (0.5) |
| LDL-cholesterol (mmol/l) | 3.1 (1.0) | 3.1 (1.0) | 3.2 (1.0) | 3.0 (1.0) |
| Triacylglycerol (mmol/l) | 1.2 [0.9–1.7] | 1.2 [0.9–1.6] | 1.2 [0.9–1.7] | 1.2 [0.9–1.7] |
| C-reactive protein (μg/ml) | 1.2 [0.6–2.6] | 1.1 [0.6–2.5] | 1.2 [0.6–2.6] | 1.2 [0.6–2.7] |
| Serum amyloid A (μg/ml) | 3.1 [2.0–5.3] | 3.2 [2.0–5.4] | 3.0 [1.9–5.1] | 3.1 [2.1–5.3] |
| sICAM-1 (ng/ml) | 335.6 [289.5–394.7] | 330.3 [280.3–392.1] | 333.4 [292.0–388.6] | 340.7 [293.5–401.8] |
| IL-6 (pg/ml) | 0.6 [0.4–0.9] | 0.5 [0.3–0.8] | 0.6 [0.4–0.9] | 0.6 [0.4–1.0] |
| IL-8 (pg/ml) | 4.1 [3.3–5.2] | 3.8 [3.1–4.8] | 4.1 [3.3–5.2] | 4.4 [3.5–5.6] |
| TNF-α (pg/ml) | 2.2 [1.9–2.5] | 2.1 [1.8–2.4] | 2.1 [1.9–2.5] | 2.5 [2.0–2.7] |
| Glucose-lowering medication (%) | 19.0 | 12.4 | 18.5 | 26.0 |
| Antihypertensive medication (%) | 37.6 | 29.6 | 34.7 | 48.2 |
| Lipid-lowering medication (%) | 34.2 | 25.9 | 33.3 | 43.3 |
| VPT (V) | 11.5 [8.0–17.7] | 9.3 [6.7–13.2] | 11.8 [8.3–17.0] | 14.7 [9.5–22.3] |
| Neuropathic pain (%) | 5.7 | 4.4 | 5.4 | 7.3 |
| Sural SNAP amplitude, range (μV)a | undetectable – 41.6 | 11.6–41.6 | 6.7–11.6 | undetectable – 6.6 |
| Sural NCV (m/s)a | 48.4 (5.8) | 49.5 (5.2) | 48.2 (5.7) | 47.0 (6.1) |
| Peroneal CMAP amplitude (mV) | 5.0 (2.1) | 5.5 (2.1) | 5.1 (2.1) | 4.5 (2.0) |
| Peroneal NCV (m/s) | 45.9 (4.7) | 47.2 (.1) | 46.0 (4.4) | 44.1 (5.0) |
| Tibial CMAP amplitude (mV) | 9.7 (4.4) | 11.2 (4.3) | 9.8 (4.1) | 8.2 (4.2) |
| Tibial NCV (m/s) | 44.0 (4.8) | 45.3 (4.6) | 44.1 (4.3) | 42.6 (5.0) |
Values are expressed as mean (SD), median [25th–75th percentile] or percentages, unless indicated otherwise
Tertiles of sural SNAP amplitudes were derived from data from the current study and do not represent clinical cut-off values
an = 2236 due to omission of undetectable sural response