Not enough physical activity can cause cancer, the first Irish study of its kind shows.
Inadequate physical activity in Ireland resulted in approximately up to 1,500 cancer cases or 5% of total cases, along with 500 deaths or 6% in specific types of cancer sites such as colorectal, breast, and endometrial in Ireland.
In the study, titled Cancer Incidence and Mortality Due to Inadequate Physical Activity from 2011 to 2015, women were found to be disproportionately affected.
There are almost 24,000 incident invasive cancers, excluding non-melanoma skin cancer, and over 9,000 cancer deaths per year here.
The number of new cases annually is estimated to double by 2045. Changing demographics, including an ageing population, are principal drivers of the increase.
The co-authors highlight that given the harm due to inadequate physical activity, urgent actions are needed to inform the public and to strengthen policy and strategy in Ireland to address this problem.
It is estimated that 30% to 50% of all cancers are preventable.
Desmond Hickey, from the National Cancer Control programme, explained there is significant evidence that physical activity protects against several cancers.
He said: “Biological mechanisms by which exercise may reduce cancer risk include the promotion of endogenous steroid hormone metabolism, decreasing circulation of oestrogens and androgens, reduction of insulin resistance and long-term inflammation, and improved immune function.
“This is the first study to calculate the Population Attributable Fraction (PAF) of inadequate physical activity on cancer incidence and mortality in Ireland. (These) findings will improve understanding of the cancer burden in Ireland,” said Mr Hickey.
The study, in this month’s Irish Medical Journal, was calculated by sex, five-year age groupings, and cancer type on people aged 20 and older.
Five hundred and 379 colorectal cancers were estimated to be preventable in men and women, respectively. This equated to 7% of all colorectal cancers in both sexes.
Over the five year period 210 colorectal cancer deaths were estimated to be preventable in men and women.
This equated to 7% and 8% of all colorectal cancers in men and women.
Of 14,710 breast cancer cases, 321 were estimated to be preventable with adequate physical activity. This equated to 2% of all breast cancers.
Of 3,496 female breast cancer deaths, 85 were estimated to be preventable with adequate physical activity. This corresponded to 2% of all breast cancer mortality.
Of some 1,953 endometrial cancers, 356 were estimated to be preventable with exercise. This corresponded to 18% of the total number of incident endometrial cancers.
Of 407 endometrial cancer deaths, 77 were estimated to be preventable, equating to 19% of total endometrial cancer mortality.
Mr Hickey added: “The key study findings were that in the five-year period, 2011-2015, over 1,500 cancer cases and 500 deaths in Ireland can be attributed to inadequate physical activity. This equated to approximately six new diagnoses and two deaths from cancer every week.
“Women were disproportionately affected. Amongst women, it was estimated over 1,000 incident cases and 300 deaths were potentially preventable, compared with 500 incident cases and more than 200 deaths in men.
It is predicted, based on demographic changes, that annual breast cancer incidence will increase by over 60% by 2045.
In total, this study found that 2% of both incident cases and deaths from female breast cancer in 2011-2015 were potentially attributable to inadequate physical activity.
“This equated to over 300 potentially preventable incident cancers and 80 deaths in the relevant time period which underscores the importance of this avoidable exposure in the female population”.