Table 2. Characteristic of study sample with and without rheumatoid arthritis.
| Without rheumatoid arthritis (n = 8,483) | Rheumatoid arthritis (n = 306) | P | |
|---|---|---|---|
| Demographic features | |||
| Age, years | 36.4 ± 20.0 | 44.6 ± 8.9 | <0.001 |
| Sex | 0.003 | ||
| Male | 4,214 (50.5) | 110 (39.0) | |
| Female | 4,269 (49.5) | 196 (61.0) | |
| Education level | 0.125 | ||
| <9th grade | 673 (4.5) | 32 (7.0) | |
| 9th–12th grade | 3,290 (34.7) | 134 (38.4) | |
| ≥13th grade | 4,510 (60.8) | 140 (54.6) | |
| Race | 0.003 | ||
| Mexican American or other Hispanic | 1,690 (11.5) | 41 (7.6) | |
| Non-Hispanic white | 3,420 (61.8) | 157 (66.8) | |
| Non-Hispanic black | 1,655 (12.5) | 71 (17.5) | |
| Others | 1,718 (14.2) | 37 (8.1) | |
| Marital status | <0.001 | ||
| Married/living with partner | 5,092 (60.4) | 165 (58.4) | |
| Widowed/divorced/separated | 1,089 (11.9) | 90 (25.3) | |
| Never married | 2,297 (27.7) | 51 (16.3) | |
| Family monthly poverty level index | 0.002 | ||
| ≥3 (not poverty) | 2,851 (48.9) | 70 (30.9) | |
| <3 (poverty) | 4,925 (51.1) | 220 (69.1) | |
| Covered by health insurance | 5,584 (73.3) | 233 (80.2) | 0.044 |
| Behavioral factors, lifestyle and health conditions | |||
| Regular smoking | 3,223 (38.3) | 171 (57.6) | <0.001 |
| Level of drinking | 0.067 | ||
| Non-drinker | 994 (11.4) | 34 (10.1) | |
| Moderate | 2,907 (39.1) | 108 (49.5) | |
| Heavy | 2,975 (44.8) | 78 (34.9) | |
| Occasional | 390 (4.7) | 14 (5.6) | |
| Body mass indexa, kg/m2 | <0.001 | ||
| <25 | 2,784 (35.1) | 64 (19.5) | |
| 25∼29.9 | 2,778 (32.9) | 70 (22.2) | |
| ≥30.0 | 2,880 (32.1) | 169 (58.3) | |
| Appropriate sleep durationb | 7,259 (87.2) | 206 (71.3) | <0.001 |
| HIV positive | 41 (0.5) | 2 (0.6) | 0.718 |
| Osteoporosis | 55 (0.8) | 15 (5.7) | <0.001 |
| Diabetes | 404 (3.6) | 58 (17.2) | <0.001 |
| Caffeine intake | 0.474 | ||
| None | 1,367 (14.2) | 40 (14.9) | |
| Recommended | 5,958 (69) | 203 (64.5) | |
| High | 1,158 (16.7) | 63 (20.6) | |
| Milk consumption | 0.594 | ||
| Never | 2,043 (22.4) | 68 (20.1) | |
| Regular | 3,552 (43.3) | 129 (47) | |
| Irregular | 2,886 (34.3) | 109 (32.8) | |
| Dietary factorsc | |||
| Higher total saturated fat intake | 119 (1.4) | 5 (1.3) | 0.914 |
| Vitamin A intake | 0.027 | ||
| Insufficient | 6,524 (75.0) | 231 (72.1) | |
| Recommended | 1,907 (24.5) | 72 (25.5) | |
| Excess (toxic) | 52 (0.6) | 3 (2.4) | |
| Inadequate vitamin B1 intake | 2,698 (30.4) | 108 (36) | 0.112 |
| Inadequate vitamin B2 intake | 1,766 (18.3) | 66 (19.8) | 0.494 |
| Inadequate vitamin B6 intake | 2,503 (28.7) | 115 (33.1) | 0.130 |
| Inadequate vitamin B12 intake | 2,316 (26.3) | 78 (22.4) | 0.232 |
| Inadequate vitamin C intake | 3,186 (36.9) | 103 (33.9) | 0.454 |
| Inadequate vitamin D intake | 8,132 (95.6) | 293 (95.7) | 0.926 |
| Inadequate vitamin E intake | 8,407 (98.7) | 304 (97.7) | 0.448 |
| Inadequate vitamin K intake | 6,240 (72.1) | 222 (70.7) | 0.682 |
| Niacin intake | 0.676 | ||
| Insufficient | 1,626 (17.8) | 58 (18.4) | |
| Recommended | 4,953 (59.6) | 188 (62) | |
| Excess | 1,904 (22.5) | 60 (19.6) | |
| Folate intake | 0.065 | ||
| Insufficient | 3,442 (39.6) | 135 (44.6) | |
| Recommended | 4,239 (50.4) | 150 (49) | |
| Excess | 802 (10.0) | 21 (6.4) | |
| Inadequate calcium intake | 5,234 (59.3) | 206 (61.8) | 0.454 |
| Inadequate iron intake | 3,704 (42.1) | 131 (40) | 0.518 |
| Inadequate magnesium intake | 6,195 (72) | 227 (73.2) | 0.670 |
| Inadequate phosphorous intake | 941 (10.3) | 44 (13.6) | 0.103 |
| Inadequate potassium intake | 7,908 (93) | 289 (92) | 0.582 |
| Excess sodium intake | 6,486 (77.9) | 213 (70.0) | 0.031 |
| Inadequate zinc intake | 3,609 (41.2) | 127 (42.6) | 0.728 |
| Inadequate copper intake | 2,648 (29.1) | 108 (36.7) | 0.018 |
| Inadequate selenium intake | 1,045 (12) | 49 (17.5) | 0.059 |
Notes.
Age was presented as mean ± standard deviation, and other data were expressed as frequency (weighted %).
a
Body mass index (BMI) <18.5 kg/m2 was defined as underweight, BMI between 18.5 and 24.9 kg/m2 as normal, BMI between 25 and 29.9 kg/m2 as overweight, and BMI ≥ 30.0 kg/m2 as obese.
b
Appropriate sleep duration was defined as the time interval ranges from 6 to 11 h for people between 18 and 25 years of age, or from 6 to 10 h for people between 26 and 64 years of age.
c
Recommended nutrient allowances are shown in Table 1.