You’d think having anorexia nervosa was bad enough. But among all the negative effects it can have on your body, could it also increase your risk of cancer? Or does the condition perversely mimic the caloric restriction and fasting that have been demonstrated to benefit the prevention of some malignancies – meaning could it protect against cancer?
That’s what European oncology researchers wanted to find out through their systematic review and meta-analysis of a series of studies involving more than 42,000 people with the eating disorder.
The result was both encouraging and intriguing.
It appears that overall there was no association of anorexia nervosa with risk of cancer.
But that’s not the whole story.
On further analysis it appears anorexia nervosa was associated with some cancers and not others. In some cases the condition increased the risk and in others it appeared protective, hence the balancing out effect of no association overall.
“Findings from our meta-analysis suggest that anorexia nervosa was associated with decreased breast cancer incidence compared with the general female population, with high confidence,” said the study authors in JAMA Network Open.
And on the down side, the researchers found anorexia nervosa appeared to be associated with an increased risk of developing lung and oesophageal cancer, although the evidence was less compelling than that for breast cancer.
As the authors point out, the breast cancer protection makes sense in terms of physiology.
Anorexia notoriously interferes with a woman’s hormones, reducing her levels of oestradiol as well as insulin-like growth factor 1. Women with anorexia often have delayed puberty, early menopause and an overall decreased lifetime exposure to oestrogen so it stands to reason that a hormone-sensitive cancer, such as breast cancer is less likely to develop.
But the increased risk of lung and oesophageal cancer is harder to explain. One might think, given the types of cancer we’re talking about that perhaps there was a greater prevalence of smoking among people with anorexia nervosa.
“[T]he increased risk of developing lung or oesophageal cancer does not seem to be attributable to a higher prevalence of smoking among women with anorexia nervosa,” they said.
Interestingly the authors refer to a 2016 meta-analysis that determined smoking prevalence was much higher among people with bulimia nervosa than the general population, but not anorexia nervosa.
The researchers offer no explanation for the association between anorexia and lung and oesophageal cancer, conceding the evidence isn’t strong. However they do warn that the findings suggest perhaps a need for greater vigilance in investigating symptoms suggestive of cancers of either the respiratory tract or the GIT in anorexia nervosa patients.
As with most studies, the study authors call for further research to confirm or refute these associations, suggesting that the findings have possibly important implications.
“Understanding the mechanisms underlying these associations could have important preventive potential,” they concluded.
Catalá-López F1, Forés-Martos J, Driver JA, Page MJ, Hutton B, Ridao M, et al. Association of Anorexia Nervosa With Risk of Cancer: A Systematic Review and Meta-analysis. JAMA Netw Open. 2019; 2(6): e195313. DOI: 10:1001/jamanetworkopen.2019.5313