Lifestyle affects cancer risk, but the biggest risk is getting old
Old age is not for the weak of heart: Nine out of ten cases of cancer occur after we reach the age of 50, new numbers from the Norwegian Cancer Registry show.
One in three people will develop cancer before they reach the age of 75. But the risk of getting cancer differs wildly depending on your age.
Your risk increases considerably by the time you reach 50, but if you reach the age of 80, your risk of getting cancer is 40 times higher than when you were in your 20s.
Nevertheless, the incidence of cancer in Norway has been stable in recent years, said Giske Ursin, head of the Cancer Registry of Norway, when she presented cancer data for 2017 in early November.
An ageing population means more cancer
Norway, like much of the rest of the Western world, is getting older. The Cancer Registry of Norway estimates that the number of cancer cases in the country will increase by 42 per cent for men and 27 per cent for women by 2030.
Ursin says a growing, and aging population explains the increase.
Getting old increases a person’s risk of cancer, because the body’s fine-tuned ability to repair DNA is eventually overwhelmed by the amount of damage due to age. That allows cells to divide uncontrollably, eventually causing the development of a cancerous tumour.
But people entering old age today may have had a number of bad habits that make them particularly vulnerable to cancer.
This means that some of the most common forms of cancer currently found in Norway are not likely to be a problem in the future for people who are now in their 20s.
Gender differences in lung cancer
Lifestyle is of great importance in causing lung cancer, the second most common cancer in both women and men. One in 25 men and one in 28 women will get lung cancer before they turn 75.
Smoking is the biggest risk factor for lung cancer, with 8 of 10 cases due to tobacco.
The incidence of lung cancer has been dropping for years among men. But it had continued to rise among women until now, when it is only women 70 years and older who have an increased risk of lung cancer. Researchers don’t really know why this is so.
One theory is that a woman's lungs are less able to handle tobacco smoke than a man's. But it may also be that men generally stopped smoking earlier than women.
"Women who are in their 70s today often started smoking when they were teenagers. Those who have not managed to quit thus have a long history of smoking, and many of these women have paid a painful price,” said Tom Grimsrud, senior medical officer in the Cancer Registry’s Etiological Research Unit.
Alcohol also poses risks
Some types of cancer are also related to our drinking habits. This is true of cancers of the oral cavity, throat, esophagus, colon, liver, and breast.
A Nordic research group that has studied the relationship between tobacco and non-lung cancers calculated how many lives could be saved in Norway if people stopped drinking alcohol.
“If all use of alcohol had ceased in 2017, we could have avoided 13,000 cases of alcohol-related cancer up to 2045,” said Grimsrud.
Eliminating alcohol would have had an especially stong reduction on the cases of breast and colon cancer, they report.
Norwegians are unlikely to stop drinking as quickly as they stopped smoking. But research shows drinking patterns have changed, especially among younger people, who in large parts of the world tend to drink less than previous generations.
On the other hand, figures from the Norwegian Institute of Public Health show that older people tend to drink more frequently than younger people, although they drink less alcohol when they do indulge.
Read more in the Norwegian version of this article at forskning.no