Study didn’t show ‘hairdressers have a higher cancer risk because of chemicals at work’

19 July 2023
What was claimed

Hairdressers have a higher cancer risk because of chemicals at work, a study shows.

Our verdict

This is not what the study says. One of its authors has confirmed the research was exploratory and established no definite associations between people’s jobs and their risk of ovarian cancer.

Hairdressers have a higher cancer risk because of chemicals at work, a study shows.

An article published by the Sun last week claimed new research shows that exposure to chemicals at work makes hairdressers and women in some other professions more likely to develop ovarian cancer.

But this is not what the research shows, and the Sun has now corrected the article after contact from Full Fact.

An author of the study in question, Dr Anita Koushik from the University of Montreal School of Public Health, told us that it was exploratory and did not establish any definite associations between people’s work and their risk of ovarian cancer.

Dr Koushik said: “The Sun has not accurately reported our work.”

The media must report scientific research accurately, and correct mistakes quickly when they happen, so that people are not misled about important risks that they might face in their daily lives. We’re grateful to the Sun for making a quick correction in this case.

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How the study worked

The study in question used data from Canada to compare the occupational histories of 491 women diagnosed with ovarian cancer with the histories of 897 women without that diagnosis. Based on this, it reported a list of occupations where ovarian cancer seemed to be more common than expected.

However, the number of women in the study who had worked in specific jobs was often very small.

For example, a total of just 44 women in the study, including those with and without ovarian cancer, had ever worked as “Hairdressers, Barbers, Beauticians and Related Workers”.

The authors concluded: “Certain occupations, industries and specific occupational exposures may be associated with ovarian cancer risk [our italics]. Further research is needed to provide a more solid grounding for any inferences in this regard.”

This means that the research did not establish any definite relationships between certain jobs and the risk of ovarian cancer, even though it did find some associations that were “statistically significant”. As the paper itself says: “It is likely that some statistically significant associations observed were due to chance given the number of analyses performed.”

The corrected version of the Sun article now only says that there “may” be a link between these jobs and ovarian cancer.

What other experts say

Commenting on the paper for the Science Media Centre, Professor Paul Pharoah, professor of cancer epidemiology at Cedars-Sinai Medical Center in Los Angeles, said: “The major problem with this study is the sample size. In total fewer than 500 women with ovarian cancer took part in the study. Consequently, the findings are not statistically robust. Given the number of occupations investigated, one or two statistically significant associations would have been expected by chance (which is what they found).

“I do not think it is possible to draw any firm conclusions about occupational exposures from the findings of this study. In particular, there is not strong evidence to suggest that either hairdressers or accountants are at increased risk of ovarian cancer and women in these occupations should not be concerned about their risk.”

Even if the associations it found turn out to be real, the study also could not establish cause and effect. In other words, it couldn’t tell us that hairdressers had a higher risk “because of chemicals at work” as the Sun reported.

Kevin McConway, Emeritus Professor of Applied Statistics at the Open University, added: “Obviously, the researchers could not make the respondents work in specific jobs. They just observed what jobs they had done, along with some other characteristics, and the study included some women (the ‘cases’) who had had ovarian cancer and some others (the ‘controls’) who had not.

“So, there are bound to be differences between the women who had and had not had ovarian cancer, apart from differences in what jobs they had done and what possibly cancer-causing agents they had been exposed to at work. These other differences might be the true cause of whether they had cancer or not, rather than the occupational differences.”

Image courtesy of Adam Winger

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