Table 1.
Characteristics of VITAL trial participants at baseline according to randomized assignment to active supplementation (vitamin D or omega 3 fatty acids) or placebo. Data are numbers (%) unless indicated otherwise
| Characteristic | Total (n=25 871) | Vitamin D | Omega 3 fatty acids | |||
|---|---|---|---|---|---|---|
| Treatment group (n=12 927) | Placebo group (n=12 944) | Treatment group (n=12 933) | Placebo group (n=12 938) | |||
| Female sex | 13 085 (50.6) | 6547 (50.7) | 6538 (50.5) | 6547 (50.7) | 6538 (50.5) | |
| Age (years), mean (SD) | 67.1 (7.1) | 67.1 (7.1) | 67.1 (7.1) | 67.2 (7.1) | 67.1 (7.1) | |
| Race or ethnic group* | ||||||
| Non-Hispanic white | 18 046 (71.3) | 9013 (71.3) | 9033 (71.4) | 9044 (71.5) | 9002 (71.2) | |
| Black | 5106 (20.2) | 2553 (20.2) | 2553 (20.2) | 2549 (20.2) | 2557 (20.2) | |
| Other | 2152 (8.5) | 1081 (8.6) | 1071 (8.5) | 1060 (8.4) | 1092 (8.6) | |
| Geographical region of residence | ||||||
| North east | 7161 (27.7) | 3603 (27.9) | 3558 (27.5) | 3544 (27.4) | 3617 (28) | |
| Midwest | 5541 (21.4) | 2774 (21.5) | 2767 (21.4) | 2790 (21.6) | 2751 (21.3) | |
| West | 5926 (22.9) | 2935 (22.7) | 2991 (23.1) | 2993 (23.1) | 2933 (22.7) | |
| South east | 7242 (28.0) | 3615 (28.0) | 3627 (28.0) | 3605 (27.9) | 3637 (28.1) | |
| Highest level of education | ||||||
| ≤High school | 3304 (12.8) | 1650 (12.8) | 1654 (12.8) | 1683 (13) | 1621 (12.6) | |
| ≥High school | 22 514 (87.2) | 11 252 (87.2) | 11 262 (87.2) | 11226 (87) | 11288 (87.4) | |
| Self-reported annual income ($)† | ||||||
| <50 000 | 8523 (36.6) | 4293 (36.9) | 4230 (36.4) | 4238 (36.4) | 4285 (36.9) | |
| ≥50 000 | 14 750 (63.4) | 7344 (63.1) | 7406 (63.6) | 7405 (63.6) | 7345 (63.2) | |
| Current supplemental vitamin D use ≤800 IU/day | 11 030 (42.6) | 5497 (42.5) | 5533 (42.7) | 5498 (42.5) | 5533 (42.7) | |
| Serum 25-hydroxyvitamin D, mean (SD) | 30.7 (10) | 30.7 (10) | 30.7 (10) | 30.7 (10) | 30.7 (10) | |
| Serum 25-hydroxyvitamin D <20 ng/mL | 2161 (12.9) | 1049 (12.5) | 1112 (13.3) | 1072 (12.8) | 1089 (13.0) | |
| Serum 25-hydroxyvitamin D <30 ng/mL | 7646 (45.6) | 3803 (45.4) | 3843 (45.9) | 3823 (45.6) | 3823 (45.7) | |
| Omega index,‡ mean (SD) | 2.6 (0.9) | 2.6 (0.9) | 2.6 (0.9) | 2.6 (0.9) | 2.6 (0.9) | |
| Body mass index,§ mean (SD) | 28.1 (5.7) | 28.1 (5.7) | 28.1 (5.8) | 28.1 (5.7) | 28.1 (5.8) | |
| Physical activity total MET hours/week, median (IQR) | 15.4 (4.6-31.6) | 15.2 (4.5-31.5) | 15.5 (4.7-32.0) | 15.5 (4.6-31.5) | 15.4 (4.5-31.7) | |
| Current smoker | 1836 (7.2) | 921 (7.2) | 915 (7.2) | 920 (7.2) | 916 (7.2) | |
| Family history of autoimmune disease | 8168 (34.3) | 4092 (34.4) | 4076 (34.3) | 4125 (34.6) | 4043 (34.1) | |
| Randomized to active group, other arm of trial | 12 933 (50.0) | 6463 (50.0) | 6470 (50.0) | 6463 (50) | 6464 (50) | |
IQR=interquartile range; MET=metabolic equivalent; SD=standard deviation.
Percentages might not add up to 100 because of rounding. No significant differences were found in baseline characteristics between groups. Race or ethnic group: n=25 304; serum vitamin D: n=16 757; omega index: n=16 478; body mass index: n=25 254; physical activity: n=25 619; smoking: n=25 485; family history: n=23 779. Number of participants with autoimmune disease self-reported at baseline: rheumatoid arthritis, 1279; polymyalgia rheumatica, 162; psoriasis, 846; autoimmune thyroid disease, 2075; other autoimmune disease, 851.
Race and ethnic group were reported by participants.
Income data missing for 10% of participants.
Serum eicosapentaenoic acid plus docosahexaenoic acid/total lipids.
Body mass index is weight in kilograms divided by square of height in meters.