Does using the contraceptive pill increase my risk of cancer?
The pill demonstrably lowers the risk of ovarian and uterine cancer, but slightly raises the risk of breast cancer with long-term use or use before a first pregnancy. Discuss your personal situation with your GP or gynaecologist if you have any doubts.
Ovarian cancer and uterine cancer are demonstrably less likely in pill users. The risk of ovarian cancer falls by around 40%, and this protective effect persists for years after stopping. Something similar applies to uterine cancer: the progestogen component in the pill suppresses cell growth in the uterine lining, and this benefit also remains after stopping.
For breast cancer the picture is more nuanced. For the average user, research covering more than 72,000 cases shows no significantly elevated risk. However, two subgroups deserve attention: women who use the pill before their first full-term pregnancy, and women who take the pill for longer than five years. In both groups the relative risk is approximately 9 to 14% higher than in non-users. That sounds alarming, but because young women already have a low baseline risk of breast cancer, the absolute extra risk is very small in numerical terms.
Current or recent use (within the past ten years) also appears to cause breast cancer that was already developing to become detectable slightly earlier. The pill probably does not create new cancer cells, but may cause cancer cells that are already present to grow a little faster. The tumours found in pill users are generally less advanced than those found in non-users. The elevated risk gradually decreases after stopping.
For cervical cancer there are indications that long-term use slightly raises the risk. However, pill users are also more frequently exposed to the HPV virus, due to a combination of behavioural factors such as reduced condom use. The pill appears to enhance the effect of HPV, but is not itself a direct cause. Regular cervical smear tests remain just as important. Whether a direct biological link exists has not yet been definitively established.
Claims are based on several large epidemiological studies and meta-analyses, including a meta-analysis of 79 studies covering more than 72,000 breast cancer cases. The associations are largely observational; randomised controlled research into cancer risks is impossible for ethical and practical reasons. None of the cited sources report any financial conflicts of interest.
Does working with pesticides increase your risk of cancer?
Working with pesticides is associated in multiple studies with an increased risk of several types of cancer, including bladder, bowel, and blood cancers. Avoiding unprotected contact is sensible, especially if you are pregnant or planning to become pregnant.
Does being overweight increase my risk of cancer, and if so, which types?
Excess weight increases your risk of at least 13 types of cancer, including uterine, colorectal, breast and liver cancer. Losing weight reduces that risk, although it remains unclear whether all methods of weight loss are equally effective for immune defence against cancer.
Does sitting a lot increase my risk of cancer, even if I exercise?
Sitting a lot increases your risk of certain cancers, even if you exercise. In addition to moving regularly, try to reduce your sitting time itself, because the two only partially compensate for each other.
Does eating a lot of sugar increase my risk of cancer?
Drinking large amounts of sugar-sweetened beverages is associated with a noticeably higher risk of certain cancers, particularly early-onset colorectal cancer and liver cancer. The association is observational, but consistent enough to make reducing soft drinks and fruit juice a concrete point of attention.
Does poor sleep increase my risk of cancer?
Poor sleep, and certainly untreated sleep apnoea, is associated with an increased cancer risk, but it has not yet been proven that sleeping poorly causes cancer. Have sleep apnoea checked if you have symptoms, and try to maintain a regular sleep schedule.
Does working at night increase my risk of cancer?
Night work probably increases the risk of breast cancer, and possibly of other types of cancer. If you have been working night shifts for years, it is worthwhile to discuss this with your doctor and to stay alert to population screening programmes.