From: Hookah smoking and cancer: carcinoembryonic antigen (CEA) levels in exclusive/ever hookah smokers
 |  | Number of daily preparations | Number of daily sessions | Total daily smoking duration | CEA mean levels (ng/ml) | p-values Smokers vs non-smokers |
---|---|---|---|---|---|---|
Light Smokers (n = 5) |  | 1 | 1 | ≤ 20 minutes | 1.06 ± 0.492 | ≤ 0.002157 |
Medium | Smokers | 1 to 3 | 1 to 3 | ≤ 2 hours | 2.52 ± 1.15 | ≤ 0.9138 |
(n=28) | ||||||
Heavy | Smokers | 2 to 4 | 3 to 8 | ≤ 6 hours | 5.11 ± 3.08 | ≤ 0.0001567 |
(n=26) | ||||||
Overall hookah | exclusive smokers | 1 to 4 | 1–8 | ≤ 20 min-6 hrs | 3.58 ± 2.61 | ≤ 0.0937 |
(n=59) | ||||||
Non-smokers (n = 36) |  | - | - | - | 2.35 ± 0.71 | - |
*Cigarette (n = 122) | smokers | - | - | - | 9.19 ± 14.9 | ≤ 5.0 × 10-7 |
*Mixed hookah/cigarette smokers (n = 14) |  | - | - | - | 7.16 ± 10.38 | ≤ 0.006069 |