Table 1.
Characteristics of the Diabetes Control and Complications Trial (DCCT)/Epidemiology of Diabetes Interventions and Complications Participants with Skin Instrinsic Fluorescence (SIF) Measures, Separately by Former DCCT Randomized Treatment Group at the Time SIF Was Measured
| Former INT (n=612) | Former CON (n=573) | |
|---|---|---|
| Demographic characteristics | ||
| Male sex | 317 (52%) | 308 (54%) |
| Age (years) | 52±7 | 51±7 |
| Diabetes duration (years) | 30.0±4.9 | 29.5±4.9 |
| Primary cohort assignmenta | 298 (49%) | 294 (51%) |
| Skin tone (arbitrary units) | 260±47 | 256±49 |
| Clinic latitude (>37°N)b | 444 (73%) | 427 (75%) |
| Smoking statusc | ||
| Never | 372 (61%) | 352 (61%) |
| Former | 154 (25%) | 149 (26%) |
| Current | 86 (14%) | 72 (13%) |
| Any eGFR <60 mL/min/1.73 m2 to date (yes)d | 40 (7%) | 44 (8%) |
| Glycemic exposure | ||
| DCCT eligibility HbA1c (%) (mmol/mol) | 9.1±1.6 (76±17) | 8.9±1.6 (74±17) |
| DCCT mean HbA1c (%) (mmol/mol) | 7.2±0.8 (55±9) | 9.0±1.3 (75±14) |
| EDIC mean HbA1c (%) (mmol/mol) | 8.0±1.1 (63±12) | 8.0±1.0 (63±11) |
| Time-weighted mean HbA1c (%) (mmol/mol)e | 8.0±0.9 (64±10) | 8.4±0.9 (68±10) |
| Mean caffeine intake during DCCT (mg/day) | 369±329 | 369±342 |
| Mean caffeine intake during EDIC (mg/d)f | 301±218 | 288±209 |
| Time between caffeine intake assessment and SIF1 (years)g | 11.1±1.1 | 11.0±1.0 |
| rs1495741 genotype (AA/AG/GG)h | 342/189/24 | 307/191/28 |
| SIF1LED 375nm, kx=0.6, km=0.2 (arbitrary units)i | 3.1±0.2 | 3.1±0.21 |
| SIF14LED 456nm, kx=0.4, km=0.8 (arbitrary units)i | 0.37±0.23 | 0.36±0.23 |
Data are n (%) or mean±SD values as indicated (n=1,185).
Two cohorts were recruited at DCCT baseline: a primary cohort (n=726) of subjects with no retinopathy and a urinary albumin excretion rate of <40 mg/24 h at baseline and a secondary cohort (n=715) of subjects exhibiting mild to moderate nonproliferative retinopathy and urinary albumin excretion rate of ≤200 mg/24 h at baseline.
Clinic latitude was categorized as a binary variable with clinics located above 37°N latitude designated as northern clinics (n=21) and those below assigned as southern clinics (n=7).
Smoking status was defined as “never smoker” (≤100 cigarettes in a subject's lifetime), “former smoker” (quit ≥1 year ago), or “current smoker” (currently smoking or smoking within the last year).
Estimated glomerular filtration rate (eGFR) was estimated using the Chronic Kidney Disease–Epidemiology Collaboration equation.
Time-weighted mean glycated hemoglobin (HbA1c) is calculated by summing (DCCT eligibility HbA1c×duration of diabetes at DCCT baseline), (DCCT mean HbA1c×years of follow-up in DCCT), and (Epidemiology of Diabetes Interventions and Complications [EDIC] mean HbA1c×years of follow-up in EDIC) and dividing by total duration of diabetes.
Two subjects in the intensive treatment (INT) group and two in the conventional treatment (CON) group did not have dietary caffeine intake available.
The minimum lag time between measures of caffeine intake during EDIC and measures of SIF was 4 years.
One hundred four subjects did not have rs1495741 genotype data available.
Ln transformed.
LED, light-emitting diode.