Table 3. Hazards ratio (HR) of respiratory tract carcinomas by incense use, Singapore Chinese Health Study 1993-2005.
| Upper respiratory tract | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Nasopharyngeal carcinoma
(NPC) |
Non-NPC carcinoma | Lower respiratory tract Lung | ||||||||
| Persons at risk | Cases
(n=175) |
HR (95% CI)* | P for trend | Cases
(n=150) |
HR (95% CI)* | P for trend | Cases
(n=821) |
HR (95% CI)* | P for trend | |
| Status of incense use | ||||||||||
| Never users | 6,144 | 20 | 1.0 (referent) | 0.54 | 10 | 1.0 (referent) | 0.12 | 72 | 1.0 (referent) | 0.76 |
| Former users | 7,997 | 20 | 0.7 (0.4-1.4) | 9 | 0.7 (0.3-1.8) | 87 | 1.1 (0.8-1.6) | |||
| Current users | 47,179 | 135 | 0.8 (0.5-1.3) | 131 | 1.4 (0.7-2.7) | 662 | 1.0 (0.8-1.3) | |||
| Duration of incense use | ||||||||||
| Non current users † | 14,141 | 40 | 1.0 (referent) | 0.93 | 19 | 1.0 (referent) | 0.03 | 159 | 1.0 (referent) | 0.75 |
| Current users with ≤40 years | 7,599 | 22 | 0.9 (0.5-1.5) | 13 | 1.2 (0.6-2.5) | 84 | 0.9 (0.7-1.2) | |||
| Current users with 41+ years | 39,580 | 113 | 1.0 (0.7-1.4) | 118 | 1.7 (1.0-2.7) | 578 | 1.0 (0.8-1.2) | |||
| Frequency and duration of incense use | ||||||||||
| Non-current users † | 14,141 | 40 | 1.0 (referent) | 0.93 | 19 | 1.0 (referent) | 0.04 | 159 | 1.0 (referent) | 0.75 |
| Current users | ||||||||||
| Less than daily use | 3,460 | 7 | 0.7 (0.3-1.5) | 9 | 1.4 (0.6-3.0) | 49 | 1.0 (0.7-1.4) | |||
| Daily use for ≤40 years | 6,981 | 22 | 1.0 (0.6-1.7) | 13 | 1.3 (0.6-2.7) | 75 | 0.9 (0.7-1.2) | |||
| Daily use for 41+ years | 36,738 | 106 | 1.0 (0.7-1.4) | 109 | 1.7 (1.0-2.8) | 538 | 1.0 (0.8-1.2) | |||
| Level of incense use | ||||||||||
| Non-current use† | 14,141 | 40 | 1.0 (referent) | 0.78 | 19 | 1.0 (referent) | 0.02 | 159 | 1.0 (referent) | 0.46 |
| Low (night/intermittent) | 40,324 | 112 | 0.9 (0.6-1.3) | 107 | 1.5 (0.9-2.5) | 569 | 1.0 (0.8-1.2) | |||
| High (day/all times) | 6,855 | 23 | 1.1 (0.7-1.9) | 24 | 2.1 (1.1-3.8) | 93 | 0.9 (0.7-1.2) | |||
*
Adjusted for age at recruitment, year of interview, gender, dialect group, level of education, body mass index, number of cigarettes/day, number of years of smoking, time since smoking cessation, alcohol consumption, dietary intakes of isothiocyanate, beta-cryptoxanthin, lutein, lycopene and summed Chinese preserved foods, and for women, number of children (see details in the Materials and Methods).
†
Including both never and former users of incense.