Street lights can increase your risk of thyroid cancer by up to 55%, study finds

Living in an area with high levels of outdoor artificial light can increase the risk of developing thyroid cancer – neon lights increasing the risk by 55%, study finds.

Researchers at the University of Texas Health Science Center looked for a link between people developing thyroid cancer and levels of artificial light outside.

They looked at data from a cohort of 464,371 participants followed for about 13 years in the NIH-AARP Diet and Health Study – then analyzed satellite images to estimate light levels in areas where lived the people involved in the study.

They found that people living in areas most polluted by night light had a 55% higher risk of developing thyroid cancer than those in areas with low light.

They believe that one reason for this link is that light at night suppresses melatonin, a modulator of estrogen activity – which may have an anti-tumor effect.

Over the past century, night landscapes – especially in cities – have changed dramatically due to the rapid growth of electric light, the study’s authors said.

Studies have also reported an association between higher levels of nighttime light measured by satellite and an increased risk of breast cancer.

As some breast cancers may share a common link with thyroid cancer, lead author Qian Xiao and his colleagues decided to look for an association between the backbone and the subsequent development of thyroid cancer.

They used the NIH-AARP Diet and Health study – containing data on hundreds of thousands of people aged 50 to 71 – recorded in 1995 and 1996.

Xiao then looked at satellite images of each of their homes to determine if people living in bright areas were more likely to develop thyroid cancer.

The team then searched the National Cancer Registry databases to identify thyroid cancer diagnoses up to 2011 and found 856 cases among the 464,371 volunteers.

“Compared to the lowest quintile of light at night, the highest quintile was associated with a 55% higher risk of developing thyroid cancer,” Xiao said.

“The association was primarily driven by the most common form of thyroid cancer, called papillary thyroid cancer, and it was stronger in women than in men,” he found.

In women, the association was stronger for localized cancer with no signs of spreading to other parts of the body, while in men, the association was stronger for more advanced stages of the cancer, found the team.

The association appears to be similar for different tumor sizes and between participants with different demographics and body mass index.

The researchers noted that more studies are needed to confirm their results.

If confirmed, it will be important to understand the mechanisms underlying the relationship between nighttime light and thyroid cancer, Xiao said.

Scientists have noted that light at night suppresses melatonin, a modulator of estrogen activity that can have important anti-tumor effects.

Additionally, light at night can lead to disruption of the body’s internal clock (or circadian rhythms), which is a risk factor for various types of cancer.

“As an observational study, our study is not designed to establish causation,” Xiao said, adding “we don’t know if higher levels of outside light at night lead to a high risk of thyroid cancer. “.

“However, given the well-established evidence supporting the role of nighttime light exposure and circadian disturbances, we hope our study will motivate researchers to further examine the relationship between nighttime light and cancer,” Dr Xiao said.

“Recently, efforts have been made in some cities to reduce light pollution, and we believe that future studies should assess whether and to what extent these efforts have an impact on human health.

The results were published in the journal Cancer.