Lamp posts can increase thyroid cancer risk by up to 55%, study shows

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

Researchers at the University of Texas Health Sciences Center looked for a link between people who develop thyroid cancer and levels of external artificial light.

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

They found that those in areas with the highest level of nocturnal light pollution had a 55% higher risk of developing thyroid cancer than those in areas with low light.

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

Over the past century, nighttime 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 measured by satellite at night light and increased risk of breast cancer.

Since some breast cancers may have a common connection with thyroid cancer, lead author Qian Xiao and colleagues decided to look for an association between night light and the later development of thyroid cancer.

They used the NIH-AARP Diet and Health Study – presenting data on hundreds of thousands of people between the ages of 50 and 71 – recorded in 1995 and 1996.

Xiao then looked at satellite images of each of his homes to determine whether those who lived in areas of high light were more likely to develop thyroid cancer.

The team then examined state cancer registry databases to identify diagnoses of thyroid cancer by 2011 and found 856 cases among the 464,371 volunteers.

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

“The association was driven mainly by the most common form of thyroid cancer, called papillary thyroid cancer, and 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 cancer, the team found.

The association appeared to be similar for different tumor sizes and among participants with different demographic characteristics and body mass index.

The researchers noted that additional studies are needed to confirm their findings.

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

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

In addition, 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 was not designed to establish causality,” said Xiao, adding “we don’t know whether higher levels of external light at night lead to an increased risk of thyroid cancer.”

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

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

The results were published in the journal Cancer.