Being more active in the morning and evening can reduce the risk of bowel cancer by 11%, according to a study that suggests the timing of peak activity may play a “crucial role” in warding off the disease.
Researchers said that highlighting specific times when physical activity was “most beneficial” could pave the way for targeted cancer prevention strategies. The findings were published in the journal BMC Medicine.
The study, led by experts from the University of Regensburg in Germanyused data from the UK Biobank to assess 86,252 people aged 42 to 79, who tracked their physical activity by wearing a device on their wrist known as an accelerometer.
Some 529 cases of bowel cancer occurred over a follow-up period of more than five years. Researchers highlighted four activity patterns: continuous day-long activity, late-day activity, morning and evening activity, and afternoon and nighttime activity.
They found that two daily peaks in activity, around 8am and 6pm, “were associated with reduced risk of colorectal cancer, beyond the benefits of overall physical activity”.
People who were active in both the early and late parts of the day had an 11% lower risk of colorectal cancer, compared with 6% for daytime activity and no change for mid-day and night. Data from those who were only active later in the day were inconclusive.
The findings hold even when factors such as smoking, shift work and other variables that can affect a person’s cancer risk are taken into account, the study found.
Prof Dr Michael Leitzmann, chairman of the department of epidemiology and preventive medicine at Regensburg, was the principal investigator for the study.
He said: “Our study highlights that not only is physical activity important in reducing the risk of colorectal cancer, but the timing of peak activities throughout the day may play a crucial role.
“By identifying specific times – early morning and late afternoon – when physical activity is most beneficial, our findings open new avenues for targeted prevention strategies.
“If confirmed by future research, this could provide a simple yet impactful way for individuals to further reduce their cancer risk by timing their exercise.”
Colon cancer, also known as colorectal cancer, can develop anywhere in the large intestine, which includes the colon and rectum. It is one of the most common cancers worldwide.
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Dr Helen Croker, Assistant Director of Research and Policy at the World Cancer Research Fund, which funded the study, said: “Being physically active is one of our cancer prevention recommendations, and we know that it reduces cancer risk. These intriguing new findings offer potential to develop more specific recommendations, including patterns and timing of physical activity, to reduce cancer risk.”
