Changes in smoking, drinking, body weight and physical activity can alter the risk of colorectal cancer (CRC), results from a large European cohort study suggest.
“This is a clear message that general practitioners and gastroenterologists could give to their patients and 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 also showed an association between weight gain and an increased risk of CRC and a reduced risk with smoking cessation. However, Botteri and his colleagues found no published research on the association of other lifestyle factors and specifically on CRC risk, they write.
To help close this gap, they followed 295,865 people participating in the European Prospective Investigation into Cancer (EPIC) for a median of 7.8 years. The participants were mostly between the ages of 35 and 70 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 based on smoking, alcohol consumption, body mass index (BMI) and physical activity. The median time between baseline and follow-up questionnaire was 5.7 years.
They scored points as shown in the table below.
| Smoking | Alcohol consumption | Physical activity* | BMI |
|---|---|---|---|
| Never smoked = 4 | Less than 6.0 g per day = 4 | Fifth quintile = 4 | Less than 22 = 4 |
| Suspended for more than 10 years = 3 | 6.0 – 11.9 g per day = 3 | Fourth quintile = 3 | 22 – 23.9 = 3 |
| Suspended for up to 10 years = 2 | 12.0-23.9 g per day = 2 | Third quintile = 2 | 24-25.9 = 2 |
| 15 or fewer cigarettes per day = 1 | 24.0-59.9 g per day = 1 | Second quintile = 1 | 26 – 29.9 = 1 |
| More than 15 cigarettes per day = 0 | 60 g or more per day = 0 | First quintile = 0 | 30 or higher = 0 |
| *In metabolic equivalent tasks. | |||
Participants’ scores ranged from 0 to 16. At baseline, the mean HLI score was 10.04. It dropped slightly to 9.95 on tracking.
Men had more favorable changes than women, and the association between HLI score and CRC risk was statistically significant only in men.
Overall, a 1-unit increase in HLI score was associated with a 3% lower risk of CRC.
When HLI scores were grouped into tertiles, improvement from “unfavorable lifestyle” (ie, 0–9) to “favorable lifestyle” (ie, 12–16) was associated with a 23% lower risk of CRC (compared to no change) . Likewise, a drop from “favorable lifestyle” to “unfavorable lifestyle” was associated with a 34% higher risk.
Changes in BMI scores from baseline showed a trend toward an association with CRC risk.
A reduction in alcohol consumption was significantly associated with a reduction in CRC risk in participants aged 55 years or younger at the start of the study.
Increasing physical activity was significantly associated with a lower risk of proximal colon cancer, especially among younger participants.
On the other hand, a reduction in smoking was associated with an increase in CRC risk. This correlation may be the result of “reverse causation,” the researchers note; that is, people could have stopped smoking because they had early symptoms of CRC. Smoking had only a marginal effect on HLI calculations in this study, as only a small proportion of participants changed their smoking rate.
Information on diet was collected only at the beginning of the study, so changes in this factor could not be measured. The researchers adjusted their analysis for diet at baseline, but acknowledge that their inability to incorporate diet into the HLI score was a limitation of the study.
Similarly, they have used education as an indicator of socio-economic status, but acknowledge that it is only a proxy.
“Therefore, the HLI score may not accurately capture the complex relationship
between lifestyle habits and CRC risk,” they write.
Still, if the results of this observational study are confirmed by other research, the findings could provide evidence for designing interventional studies to prevent CRC, they conclude.
The study was supported by a LIBERTY grant from the French Institut National du Cancer. EPIC coordination is financially supported by the International Agency for Research on Cancer and the Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, which has additional infrastructural support provided by the NIHR Imperial Biomedical Research Centre. National cohorts are encouraged Danish Cancer Society (Denmark); Ligue Contre le Cancer, Institut Gustave Roussy, Mutuelle G’en’erale de l’Education Nationale and Institut National de la Sant’e et de la Recherche M’edicale (France); German Cancer Aid, German Cancer Research Center, German Institute of Human Nutrition Potsdam-Rehbruecke and Federal Ministry of Education and Research (Germany); Associazione Italiana per la Ricerca sul Cancro-Italy, Compagnia di SanPaolo and National Research Council (Italy); Dutch Ministry of Public Health, Social Welfare and Sport, Dutch Cancer Registry, LK Research Funds, Dutch Prevention Funds, Dutch ZON (Zorg Onderzoek Nederland), World Cancer Research Fund and Statistics Netherlands; Health Research Fund – Instituto de Salud Carlos III, Regional Governments of Andalusia, Asturias, Basque Country, Murcia and Navarre and Catalan Oncology Institute (ICO) (Spain); The Swedish Cancer Society and the Swedish Research Council and the county councils of Skane and V¨asterbotten (Sweden); and Cancer Research UK and the Medical Research Council. The researchers reported no relevant financial relationships.
Am J Gastroenterol. Published online 2 December 2022. Abstract
Laird Harrison writes about science, health and culture. His work has appeared in national magazines, newspapers, public radio and websites. He is working on a novel about alternate realities in physics. Harrison teaches writing at the Writers Grotto. Visit him at www.lairdharrison.com or follow him on Twitter: @LairdH
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