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Table 1 Characteristics by vitamin D status of Caucasian and African American ARIC study participants classified as having diabetes, with gradable eye photo at visit 3 (1993–95), and available serum 25(OH)D concentrations at visit 2 (1990–92) (N = 1339)

From: Adequate vitamin D status is associated with the reduced odds of prevalent diabetic retinopathy in African Americans and Caucasians

  N Vitamin D status defined by serum 25(OH)D concentrations (nmol/L) p value r (p value)a
<30 deficient n = 96 (7 %) 30 to <50 Inadequate n = 454 (34 %) 50 to <75 Adequate n = 577 (43 %) ≥75 adequate n = 212 (16 %)   
Season-adjusted serum 25(OH)D, mean (SD) 1339 24.5 (4.9) 41.7 (5.5) 61.2 (6.9) 88.6 (15.2) <0.001 NA
Prevalence of retinopathy, n (% yes) 1339 28 (29.2 %) 111 (24.4 %) 115 (19.9 %) 26 (12.3 %) <0.001 §
Severity of retinopathy, n (%)       0.005 §
 None 1059 68 (70.8 %) 343 (75.6 %) 462 (80.1 %) 186(87.7 %)   
 Mild NPDR 207 22 (22.9 %) 82 (18.1 %) 88 (15.3 %) 15 (7.1 %)   
 Moderate/severe NPDR 44 3 (3.1 %) 21 (4.6 %) 15 (2.6 %) 5 (2.4 %)   
 Proliferative DR 29 3 (3.1 %) 8 (1.8 %) 12 (2.1 %) 6 (2.8 %)   
Demographics
 Age (years), mean (SD) 1339 56.4 (5.7) 57.0 (5.6) 57.7 (5.6) 57.9 (5.5) 0.046 0.08 (0.003)
 Sex, n (% women) 1339 78 (81.3 %) 293 (64.5 %) 254 (44.0 %) 85 (40.1 %) <0.001 §
 Race, n (% Caucasians) 1339 38 (39.6 %) 249 (54.8 %) 428 (74.2 %) 191 (90.1 %) <0.001 §
 Field center, n (%)       <0.001 §
Forsyth County, NC 308 20 (20.8 %) 92 (20.3 %) 136 (23.6 %) 60 (28.3 %)   
 Jackson, MS 374 50 (52.1 %) 168 (37.0 %) 137 (23.7 %) 19 (9.0 %)   
 Minneapolis, MN 286 14 (14.6 %) 83 (18.3 %) 136 (23.6 %) 53 (25.0 %)   
 Washington County, MD 371 12 (12.5 %) 111 (24.4 %) 168 (29.1 %) 80 (37.7 %)   
Educationb, n (%)—visit 1       0.025 §
 Basic or 0 years 370 25 (26.0 %) 126 (27.9 %) 154 (26.7 %) 65 (30.7 %)   
 Intermediate 559 34 (35.4 %) 193 (42.8 %) 230 (39.9 %) 102 (48.1 %)   
 Advanced 407 37 (38.5 %) 132 (29.3 %) 193 (33.4 %) 45 (21.2 %)   
Health and lifestyle characteristics
Duration of diabetes, n (%)—visit 3       0.572 §
 <3 years 300 26 (27.1 %) 89 (19.6 %) 131 (22.7 %) 54 (25.5 %)   
 3 to <6 years 293 18 (18.8 %) 106 (23.3 %) 125 (21.7 %) 44 (20.8 %)   
 ≥6 years 746 52 (54.2 %) 259 (57.0 %) 321 (55.6 %) 114 (53.8 %)   
Smoking status, n (%)       0.034 §
 Current 257 21 (21.9 %) 97 (21.5 %) 105 (18.2 %) 34 (16.0 %)   
 Former 535 30 (31.3 %) 168 (37.2 %) 232 (40.2 %) 105 (49.5 %)   
 Never 545 45 (46.9 %) 187 (41.4 %) 240 (41.6 %) 73 (34.4 %)   
Vitamin D intake (IU/day), mean (SD)—visit 1 1305 164.2 (117.3) 232.5 (154.4) 239.7 (151.7) 261.8 (147.4) <0.001 0.16 (<0.001)
Vitamin D supplement, n (% yes)—visit 3 1330 0 (0.0 %) 8 (1.8 %) 9 (1.6 %) 6 (2.8 %) 0.352 §
Fish oil supplement use, n (% yes)—visit 3 1330 0 (0.0 %) 13 (2.9 %) 12 (2.1 %) 6 (2.8 %) 0.362 §
Drinking status, n (%)       0.056 §
 Current 616 37 (38.5 %) 191 (42.2 %) 277 (48.0 %) 111 (52.4 %)   
 Former 364 24 (25.0 %) 131 (28.9 %) 155 (26.9 %) 54 (25.5 %)   
 Never 358 35 (36.5 %) 131 (28.9 %) 145 (25.1 %) 47 (22.2 %)   
Waist circumference (cm), mean (SD) 1337 112.2 (15.5) 109.2 (15.8) 106.9 (13.2) 102.9 (12.5) <0.001 −0.16 (<0.001)
BMI category (kg/m2), n (%)       <0.001 −0.19 (<0.001)
 Under/normal weight (<25 kg/m2) 164 6 (6.3 %) 45 (10.0 %) 70 (12.2 %) 43 (20.4 %)   
 Overweight (25–30 kg/m2) 427 24 (25.0 %) 135 (29.9 %) 182 (31.6 %) 86 (40.8 %)   
 Obese (≥30 kg/m2) 744 66 (68.8 %) 272 (60.2 %) 324 (56.3 %) 82 (38.9 %)   
Composite physical activity index—visit 1, mean (SD) 1335 2.2 (1.4) 2.7 (1.5) 3.0 (1.5) 3.3 (1.4) <0.001 0.20 (<0.001)
Average diastolic blood pressure (mmHg), mean (SD) 1339 73.3 (9.3) 73.4 (11.3) 72.7 (10.3) 72.1 (9.5) 0.435 −0.03 (0.238)
Average systolic blood pressure (mmHg), mean (SD) 1339 127.9 (19.4) 129.0 (20.4) 126.0 (18.6) 125.1 (16.9) 0.028 −0.07 (0.008)
Hypertensionc, n (% yes) 1339 56 (58.3 %) 258 (56.8 %) 317 (54.9 %) 107 (50.5 %) 0.424 §
Hematocrit (%), mean (SD) 1333 39.7 (4.2) 40.6 (3.8) 41.7 (3.7) 41.9 (3.4) <0.001 0.17 (<0.001)
Total cholesterol (mg/dL), mean (SD) 1337 213.8 (38.0) 210.2 (40.5) 213.6 (41.9) 212.8 (42.5) 0.586 0.02 (0.406)
HDL (mg/dL), mean (SD) 1336 44.7 (12.0) 44.2 (14.4) 41.0 (13.4) 42.6 (14.2) 0.001 −0.09 (0.002)
LDL (mg/dL), mean (SD) 1279 138.8 (36.0) 133.2 (35.0) 135.5 (36.6) 133.9 (37.5) 0.504 0.01 (0.668)
Triglycerides (mg/dL), mean (SD) 1336 155.3 (82.2) 166.2 (98.3) 192.0 (132.0) 182.7 (104.9) <0.001 0.08 (0.004)
Glucose (mg/dL), mean (SD) 1339 184.2 (89.5) 177.6 (76.6) 171.6 (74.7) 156.1 (62.3) 0.002 −0.11 (<0.001)
Glycosylated hemoglobin (%), mean (SD) 1339 7.8 (2.1) 7.7 (2.1) 7.4 (1.9) 6.9 (1.6) <0.001 −0.14 (<0.001)
Insulin use in the past 2 weeks, n (% yes) 1339 16 (16.7 %) 81 (17.8 %) 70 (12.1 %) 25 (11.8 %) 0.039 §
  1. Characteristics assessed at visit two unless otherwise noted
  2. Individuals with diabetes were participants who had one of the following: (1) an 8 h fasting glucose ≥126 mg/dL, (2) a non-fasting glucose ≥200 mg/dL, (3) use of diabetes medication in the past 2 weeks, or (4) self-reported being told by a doctor that they had diabetes
  3. §Correlation coefficient not presented because characteristic was not a continuous variable
  4. aSpearman correlation coefficient and associated p value for the correlation between season-adjusted serum 25(OH)D and the respective continuous variable
  5. bEducation defined as Basic or 0 years (≤11 years or less, i.e., high school with no degree or less), Intermediate (12–16 years, i.e., high school graduate or vocational school), advanced (17–21 years, i.e., college or higher)
  6. cAverage systolic blood pressure ≥140 mm Hg, or diastolic ≥90 mm Hg, or high blood pressure medication use in the past 2 weeks