Table 1. Characteristics of the study population among tertiles of total hydrocarbons (THC) exposure.
| Characteristics | Tertiles of average daily THCa, n (%) | P valueb | Total (n = 837,917) |
||
|---|---|---|---|---|---|
| T1 (lowest) (n = 279,308) |
T2 (n = 280,917) |
T3 (highest) (n = 277,692) |
|||
| Retinal vein occlusion | 115 (0.04) | 254 (0.1) | 1,138 (0.4) | <0.001 | 1,507 (0.2) |
| Age, years | <0.001 | ||||
| Mean ± SD | 30.5 ± 20.8 | 31.9 ± 19.6 | 37.2 ± 20.3 | 33.2 ± 20.4 | |
| Gender | <0.001 | ||||
| Male | 137,707 (49.3) | 144,907 (51.6) | 148,915 (53.6) | 431,529 (51.6) | |
| Coronary artery disease | 30,030 (10.8) | 28,301 (10.1) | 31,596 (11.4) | <0.001 | 89,927 (10.9) |
| Chronic kidney disease | 14,224 (5.1) | 14,362 (5.1) | 20,036 (7.2) | <0.001 | 48,622 (5.9) |
| Chronic obstructive pulmonary disease | 22,986 (8.2) | 22,235 (7.9) | 24,279 (8.7) | <0.001 | 69,500 (8.4) |
| Asthma | 28,878 (10.3) | 24,097 (8.6) | 19,981 (7.2) | <0.001 | 72,956 (8.8) |
| Arrhythmia | 33,141 (11.9) | 29,563 (10.5) | 27,282 (9.8) | <0.001 | 89,986 (10.8) |
| Cerebrovascular diseases | 20,449 (7.3) | 20,374 (7.3) | 26,860 (9.7) | <0.001 | 67,683 (8.2) |
| Hypertension | 50,865 (18.2) | 47,434 (16.9) | 41,124 (14.8) | <0.001 | 139,423 (16.7) |
| Diabetes mellitus | 34,712 (12.4) | 33,632 (12.0) | 36,014 (13.0) | <0.001 | 104,358 (12.6) |
| Hyperlipidemia | 51,681 (18.5) | 50,194 (17.9) | 41,231 (14.8) | <0.001 | 143,106 (17.0) |
| Smoking-related diagnosis | 12,543 (4.5) | 13,670 (4.9) | 15,374 (5.5) | <0.001 | 41,587 (5.0) |
| Morbid obesity | 2,413 (0.9) | 2,354 (0.8) | 1,964 (0.7) | <0.001 | 6,731 (0.8) |
| Glaucoma | 7,064 (2.5) | 7,707 (2.7) | 7,088 (2.6) | <0.001 | 21,859 (2.6) |
| Hypercoagulable state | 1,452 (0.5) | 1,550 (0.6) | 2,427 (0.9) | <0.001 | 5,429 (0.7) |
| Retinal arteriolar disorder | 91 (0.03) | 94 (0.03) | 117 (0.04) | 0.116 | 302 (0.04) |
Note: SD, standard deviation.
aTertile values in ppm were as follows: T1 level: < 2.28, T2 level: ≥ 2.28 and < 2.40, T3 level: ≥ 2.40.
bThe chi-squared test or one-way analysis of variance among tertiles of total hydrocarbons.