Table 1.
Baseline Characteristics of Case and Control Groups of Southwestern American Indians in Arizona Who Were Screened for Diabetes Between 1982 and 2007
| Variable | Controls (n = 150) |
Cases (n = 150) |
P Valuea | ||
|---|---|---|---|---|---|
| Mean (SD) | Median (IQR) | Mean (SD) | Median (IQR) | ||
| Age, years | 31.6 (8.0) | 33.0 (6.9) | 0.10 | ||
| Body mass indexb | 30.2 (5.7) | 35.1 (6.9) | <0.0001 | ||
| Systolic blood pressure, mm Hgc | 115 (15) | 116 (14) | 0.66 | ||
| Fasting plasma glucose, mmol/L | 5.2 (0.4) | 5.5 (0.6) | <0.0001 | ||
| 2-hour postload plasma glucose, mmol/Lc | 5.6 (1.2) | 6.8 (1.6) | <0.0001 | ||
| Albumin:creatinine ratio, mg/g | 7.8 (4.8, 13.6) | 7.6 (5.0, 13.1) | 0.93 | ||
| Total arsenic, µg/Ld | 20.7 (14.9, 29.9) | 22.1 (15.8, 29.1) | 0.97 | ||
| Arsenobetaine, µg/Ld | 0.3 (0.2, 1.1) | 0.3 (0.1, 1.1) | 0.73 | ||
| Inorganic arsenic, µg/Ld | 6.9 (4.2, 9.7) | 7.0 (5.0, 9.3) | 0.44 | ||
| DMA, µg/Ld | 9.8 (6.3, 15.2) | 10.2 (6.5, 14.4) | 0.84 | ||
| MMA, µg/Ld | 2.4 (1.6, 3.6) | 2.0 (1.2, 3.0) | 0.04 | ||
| %DMAe | 53.8 (46.3, 61.4) | 53.9 (45.2, 61.0) | 0.88 | ||
| %MMAe | 13.0 (9.5, 17.0) | 10.5 (7.5, 15.0) | 0.01 | ||
| % methylation capacitye | 67.5 (59.7, 74.5) | 66.4 (58.5, 72.9) | 0.33 | ||
| Storage time, years | 23.2 (21.2, 25.1) | 24.0 (21.7, 25.4) | 0.14 | ||
| Follow-up time, years | 18.3 (16.5,20.8) | 11.4 (6.7,15.6) | <0.0001 | ||
Abbreviations: DMA, dimethylarsinic acid; IQR, interquartile range; MMA, monomethylarsonic acid; SD, standard deviation.
a P values (2-sided) were based on Student's t test for normally distributed variables and on the Kruskal-Wallis test for non–normally distributed variables.
b Weight (kg)/height (m)2.
c Information on systolic blood pressure was missing for 3 subjects, and information on 2-hour postload plasma glucose was missing for 5 subjects.
d Values were adjusted for urinary creatinine concentration.
e %DMA = DMA/(total arsenic – arsenobetaine) × 100; %MMA = MMA/(total arsenic – arsenobetaine) × 100; % methylation capacity = [(MMA + DMA)/(total arsenic – arsenobetaine)] × 100.