Changes regarding smoking, drinking, body weight, and physical activity may alter the risk for colorectal cancer (CRC), the results of a study on a large European cohort suggest.
“This is a clear message that practicing clinicians and gastroenterologists could give to their patients and to CRC screening participants to improve CRC prevention,” write Edoardo Botteri, PhD, Cancer Registry of Norway, Oslo, and colleagues in an article published in the American Journal of Gastroenterology.
Previous studies have shown a correlation between cancer in general and unhealthy lifestyle factors. They have also shown an association between weight gain and an increased risk for CRC and a reduced risk with smoking cessation. But Dr. Botteri and colleagues could not find any published research on the association of other lifestyle factors and the risk for CRC specifically, they write.
To help fill this gap, they followed 295,865 people who participated in the European Prospective Investigation into Cancer (EPIC) for a median of 7.8 years. The participants were mostly aged from 35 to 70 years and lived in Denmark, France, Germany, Greece, Italy, the Netherlands, Norway, Spain, Sweden, and the United Kingdom.
The researchers calculated a healthy lifestyle index (HLI) score on the basis of smoking status, alcohol consumption, body mass index, and physical activity. The median time between baseline and the follow-up questionnaire was 5.7 years.
They awarded points as indicated in the following table.
Participants’ scores ranged from 0 to 16. At baseline, the mean HLI score was 10.04. It dipped slightly to 9.95 at follow-up.
Men had more favorable changes than women, and the associations between the HLI score and CRC risk were only statistically significant among men.
Overall, a 1-unit increase in the HLI score was associated with a 3% lower risk for CRC.
When the HLI scores were grouped into tertiles, improvements from an “unfavorable lifestyle” (0-9) to a “favorable lifestyle” (12-16) were associated with a 23% lower risk for CRC (compared with no change). Likewise, a decline from a “favorable lifestyle” to an “unfavorable lifestyle” was associated with a 34% higher risk.
Changes in the BMI score from baseline showed a trend toward an association with CRC risk.
Decreases in alcohol consumption were significantly associated with a reduction in CRC risk among participants aged 55 years or younger at baseline.
Increases in physical activity were significantly associated with a lower risk for proximal colon cancer, especially in younger participants.
On the other hand, reductions in smoking were associated with an increase in CRC risk. This correlation might be the result of “inverse causation,” the researchers note; that is, people may have quit smoking because they experienced early symptoms of CRC. Smoking had only a marginal influence on the HLI calculations in this study because only a small proportion of participants changed their smoking rates.
Information on diet was collected only at baseline, so changes in this factor could not be measured. The researchers adjusted their analysis for diet at baseline, but they acknowledge that their inability to incorporate diet into the HLI score was a limitation of the study.
Similarly, they used education as a marker of socioeconomic status but acknowledge that this is only a proxy.
“The HLI score may therefore not accurately capture the complex relationship between lifestyle habits and risk for CRC,” they write.
Still, if the results of this observational study are confirmed by other research, the findings could provide evidence to design intervention studies to prevent CRC, they conclude.
The study was supported by the grant LIBERTY from the French Institut National du Cancer. Financial supporters of the national cohorts and the coordination of EPIC are listed in the published study. The researchers reported no relevant financial relationships.
A version of this article first appeared on Medscape.com.