Table 3 shows the association between incense
use and the risk of 3 groups of respiratory tract carcinomas. Compared with never-users, current use of
incense was not found to be associated with an
increased risk of NPC or lung carcinoma. In contrast,
incense use was associated with an increased risk of
carcinoma of the upper respiratory tract other than
the nasopharynx. The association between incense
use and cancer risk was found to be dose-dependent,
with high risk for long-term (Pfor trend 5.04) and
frequent use (P for trend 5.02). Compared with
nonusers, daily users with >40 years of incense
exposure had a statistically significant 70% increase
in their risk of non-NPC upper respiratory tract carcinoma (95% CI, 1.0-2.8; P5.04). Individuals who
used incense during the day or ‘at all times’ had a
relative risk of 2.1 (95% CI,1.1-3.8;P5.02).