Taller people have a higher risk of developing a large range of cancers, said scientists from a Cancer UK-funded study published online in The Lancet on Thursday. Although the main study used data on women, in a radio interview, one of the researchers said when they widened their analysis to include men and ethnic groups from around the world, they found the same result: “being tall increases the risk of cancer like smoking one cigarette a day”.

Researchers from the Million Women Study said the study helps us better understand how cancer develops. But right now, they have no explanation for why being taller, in biological terms, should raise a person’s risk of developing cancer.

On BBC Radio 4’s “Today” programme on Thursday morning, one of the researchers, Professor Dame Valerie Beral, said they wondered if it could be that taller people have more cells so increasing the odds of having rogue cells, but when they investigated further, they were surprised to find we don’t know for sure whether taller people have more cells.

Previous studies have found links between being tall and raised risk of cancer, but this study confirms the link for a large range of cancers, and that this is independent of lifestyles and economic circumstances.

The researchers found that every 10 cm of height (4 inches) increased a woman’s risk of cancer by about 16 per cent. Beral said in her interview this was about the same size of effect as smoking one cigarette a day, and it would be the same for men and women all over the world.

The Million Women Study is the largest study so far to investigate cancer risk in women. It is funded by Cancer Research UK, the NHS Cancer Screening Programme and the Medical Research Council.

For their paper, the authors analyzed data on 1,297,124 middle-aged women, among whom 97,376 cancers were diagnosed during a median follow up of 9.4 years per woman (a total of 11.7 million person-years). They also widened their analysis and pooled this data with that of 10 other studies, to see how the link between height and risk of cancer might vary around the world.

The results showed that:

  • The relative risk (RR) for total cancer was 1.16 (95% Confidence Interval CI ranging from 1·14 to 1·17; p

The researchers concluded that:

“Cancer incidence increases with increasing adult height for most cancer sites. The relation between height and total cancer RR is similar in different populations.”

Lead author Dr Jane Green, from the Cancer Epidemiology Unit at the University of Oxford, said in a statement that:

“The fact that the link between height and cancer risk seems to be common to many different types of cancer in different people suggests there may be a basic common mechanism, perhaps acting early in peoples’ lives, when they are growing.”

“Of course people cannot change their height. And being taller has actually been linked to a lower risk of other conditions, such as heart disease,” she added.

Speculating on what might lie behind the link between height and cancer risk, the researchers suggest it could be to do with hormone levels during childhood growth, which have an effect on risk later in life. And although they considered whether it might be because taller people have more cells, as Beral said on the radio, there isn’t enough evidence to support this.

The average European has grown in height by about 1 cm (0.39 in) every ten years in the 20th century, and this could explain about 10 to 15% of the rise in cancer cases at around the same time, said the researchers.

Sara Hiom, Cancer Research UK’s director of health information, told the press that tall people should not worry about these results:

“Most people are not a lot taller (or shorter) than average, and their height will only have a small effect on their individual cancer risk,” she said, adding that these results confirm the association between height and cancer, and pave the way for further researcher to help us understand why.

“On average, people in the UK have a more than one in three chance of developing cancer in their lifetime. So it’s important that everyone is aware of what is normal for their body and go see their doctor as quickly as possible if they notice any unusual changes,” said Hiom.

While we can’t control how tall we are, there are still many lifestyle choices we make that have a much bigger impact on reducing the risk of cancer, “such as not smoking, moderating alcohol, keeping a healthy weight and being physically active,” she added.

“Height and cancer incidence in the Million Women Study: prospective cohort, and meta-analysis of prospective studies of height and total cancer risk.”
Jane Green, Benjamin J Cairns, Delphine Casabonne, F Lucy Wright, Gillian Reeves, Valerie Beral, for the Million Women Study collaborators
The Lancet Oncology, 21 July 2011; DOI: 10.1016/S1470-2045(11)70154-1
Link to Abstract.

Additional sources: Cancer Research UK, BBC Radio 4 “Today”.

Written by: Catharine Paddock, PhD