Abstract
Background
Opium use has been associated with an increased risk of cancers of the lung, oesophagus, and pancreas, and it was recently classified by the International Agency for Cancer Research as carcinogenic to humans. It is not clear whether opium also increases the risk of colorectal cancer (CRC). The aim of our study was to assess the association between various metrics of opium use and the risk of CRC.
Methods
This case-referent study from seven provinces in Iran comprised 848 CRC cases and 3215 referents. Data on opium use (duration, amount, frequency) and potential confounders were collected by trained interviewers. Multivariable unconditional logistic regression models were used to measure odds ratios (OR) adjusted for age, gender, province, marital status, family history of CRC-linked cancers, consumption of red meat, fruits and vegetables, body shape, occupational physical activity, and socioeconomic status.
Results
Regular opium consumption was not associated with the risk of CRC (OR 0.9, 95% confidence interval, CI: 0.7, 1.2) compared to subjects who never used opium. However, frequent opium use more than twice a day was associated with an increased risk of CRC compared to non-users of opium (OR: 2.0, 95% CI: 1.1, 3.8; p for quadratic trend 0.008).
Conclusion
There seems to be no overall association between opium use and CRC, but the risk of CRC might be increased among persons who use opium many times a day.
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Authors’ contributions
MH did the literature review. HR, AN, MGH, MM, EM, RS, MS, BH, MB, RA, VA, SSH, AN, FN, AM, and AR contributed to data collection. FZ, RM, and MN provided clinical consultation. MH, HP, AR, RM, PB, EW, FK, KZ, and EP designed the study. MH and EP did the data analysis, interpreted data, and prepared the manuscript draft. All authors critically appraised the drafts of the manuscript and approved the final version. KZ is the guarantor of the study.
Authors’ disclaimer
Where authors are identified as personnel of the International Agency for Research on Cancer/World Health Organization, the authors alone are responsible for the views expressed in this article, and they do not necessarily represent the decisions, policies, or views of the International Agency for Research on Cancer/World Health Organization.
Ethical approval
The study was approved by the Ethics Committee of the National Institute of Medical Research Development (NIMAD) in Iran (Code: IR.NIMAD.REC.1394.027).
Consent to participate
Written informed consent was obtained from the parents.
Disclosure statement
There is no competing interest between authors.
Data availability statement
The data underlying this article cannot be shared publicly due to privacy of individuals that participated in the study. The data may be shared on reasonable request to the corresponding author.