The association of smoking and alcohol in colorectal cancer in black patients - Case-control study.

Background: Studies have focused on smoking and alcohol as risk factors for colorectal cancer (CRC). Caucasians and other populations have been studied worldwide, and both smoking and alcohol have been validated as causes of CRC. However, there are limited data on the black population; studies that have been performed in Africa have not specifically focused on these two risk factors but rather in combination with other risks.

Aim: To determine how smoking and alcohol affect the incidence of CRC in the African black population.

Setting: Steve Biko Academic Hospital's gastrointestinal clinic.

Methods: Subjects used for the study included black African patients above 18 years who had undergone a colonoscopy for suspected CRC between 2016 and 2018. Cases used were confirmed CRC on histology; controls were negative on histology. A minimum of 68 cases and 136 controls were needed for this study according to sample calculation. Hundred and ten cases and 220 controls were obtained in the final analysis. Data were collected between June 2019 and March 2020.

Results: Smoking (odds ratio [OR] = 1.795, p = 0.049) was a significant risk factor for CRC among black patients who presented at the gastrointestinal clinic. Age > 50 years (OR = 3.742, p < 0.001), family history (OR = 12.457, p < 0.001), and the combination of smoking and alcohol (OR = 5.927, p = 0.008) were significant risk factors. Interestingly, alcohol alone was protective (OR = 0.205, p < 0.001).

Conclusion: Both smoking and a combination of alcohol and smoking are significant risk factors in the development of CRC in the black African population.

Contribution: Smoking, as in most population groups, is a risk factor for CRC. The observed protective role of alcohol needs to be confirmed in larger studies representing the African population.