Not enough physical activity can cause cancer, the first Irish study of its kind shows.
Inadequate physical activity in Ireland resulted in up to 1,500 cancer cases or five per cent of total cases while 500 deaths or six per cent in specific types of cancer sites such as colorectal, breast, and endometrial in Ireland.
Women, the study titled Cancer Incidence and Mortality Due to Inadequate Physical Activity from 2011 to 2015 found were 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 per cent to 50 per cent of all cancers are preventable. Desmond Hickey, from the National Cancer Control programme said there is significant evidence that physical activity protects against several cancers.
“Biological mechanisms by which exercise may reduce cancer risk include 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 grouping, 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 seven per cent 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, respectively. This equated to seven per cent and eight per cent of all colorectal cancers in men and women, respectively.
Adequate physical activity
Of 14,710 breast cancer cases, 321 were estimated to be preventable with adequate physical activity. This equated to two per cent of all breast cancers. Of 3,496 female breast cancer deaths, 85 were estimated to be preventable with adequate physical activity. This corresponded to two per cent of all breast cancer mortality.
Some 1,953 endometrial cancers, 356 were estimated to be preventable with exercise. This corresponded to 18 per cent of the total number of incident endometrial cancers. Of 407 endometrial cancer deaths, 77 were estimated to be preventable, equating to 19 per cent 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 per cent by 2045. In total, this study found that two per cent 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.”