Living in a bustling metropolis may increase the likelihood of developing breast cancer compared to living in the countryside, a study suggests.
Researchers found high levels of exposure to artificial outdoor light at night time could increase the risk of the disease by 10 per cent in post-menopausal women.
Although the study does not provide an explanation for the link, previous research has found that artificial light can interfere with the production of the hormone melatonin, which inhibits the growth of certain cancer cells.
Breast cancer affects more than two million women globally ever year and claims the lives of 11,500 women in the UK alone every 12 months.
Researchers found high levels of exposure to artificial light at night could increase risk of the breast cancer by 10 per cent in post-menopausal women (stock)
A 16-year study compared rates of breast cancer in almost 200,000 women with satellite images of outdoor light pollution around where they lived.
Scientists at the National Cancer Institute in the US only assessed women that had already been through the menopause, as very little research previously looked into this demographic.
Dr Rena Jones, who was involved in the research, said: ‘The small number of studies to investigate this question have often relied on subjective exposure data and yielded inconsistent results.
‘We utilised an objective exposure measure – estimated outdoor light at night from satellite data.
‘It will be important for future studies to accurately measure light at night exposure for individuals using a combination of objective measures, carefully designed questionnaires, and personal measurement devices.’
The study, published today in the International Journal of Cancer, does not provide an explanation behind the link as it was only an observational assessment.
However, previous research has found the issue may be the artificial light interfering with the production of a chemical called melatonin.
Melatonin is also heavily involved in controlling how the body recovers during sleep and it helps regulate the body’s anticipation of darkness.
Lab test have also found that the presence of melatonin can prevent tumours from growing.
It is possible that artificial light interrupts the body’s natural circadian rhythm and therefore reduces the amount of melatonin the body produces, scientists say.
The researchers from the NIH add that various other factors can influence a person’s risk of developing breast cancer.
‘Our findings also suggested that the relationship between LAN and breast cancer risk may differ by individual characteristics, such as smoking, alcohol drinking, sleep duration and BMI, and neighbourhood environment,’ they write.
Living in a bustling metropolis may increase the likelihood of developing breast cancer compared to living in the countryside, a study of almost 200,000 women and satellite data suggests (stock photo)
Air pollution is also a known risk factor for cancer. Research from South Korea published in March of this year in Scientific Reports, for example, found ‘ambient air pollutant concentrations were positively and significantly associated with the breast cancer incidence rate’.
This included carbon monoxide (eight per cent increased risk), nitrogen dioxide (14 per cent), sulphur dioxide (four per cent), and particulate matter 10 micrometes in size, called PM10, (13 per cent).
A 2018 study led by researchers from the University of Exeter and the Barcelona Institute for Global Health found the new generation of LED streetlamps are worse for causing cancer than the older, yellow lights.
The research found high exposure to LED lights can double the risk of prostate cancer compared to non-LED lights.
LEDs also made it 1.5 times more likely that a person would develop breast cancer, the study found.
The latest study focused on outdoor light levels, but a 2018 paper published in the British Journal of cancer found indoor light does not have an impact on cancer risk.
Institute of Cancer Research scientists assessed how much artificial light a person used in their bedroom. A questionnaire gathered data on more than 100,00 Britons.
It found no association between levels of indoor light at night and breast cancer risk.
These findings were echoed in a 2019 study, also published in the British Journal of Cancer, which assessed cancer risk in 102,869 women between 2003 and 2014.
Of these women, 2,059 developed breast cancer. However, the researchers found working at night under artificial light does not increase the risk of the disease.
‘There was a significant trend with average hours of night work per week, but no significantly raised risks for hours worked per night, nights worked per week, average hours worked per week, cumulative years of employment, cumulative hours, time since cessation, type of occupation, age starting night shift work, or age starting in relation to first pregnancy,’ they write in the study.
Breast cancer is one of the most common cancers in the world and affects more than two MILLION women a year
Breast cancer is one of the most common cancers in the world. Each year in the UK there are more than 55,000 new cases, and the disease claims the lives of 11,500 women. In the US, it strikes 266,000 each year and kills 40,000. But what causes it and how can it be treated?
What is breast cancer?
Breast cancer develops from a cancerous cell which develops in the lining of a duct or lobule in one of the breasts.
When the breast cancer has spread into surrounding breast tissue it is called an ‘invasive’ breast cancer. Some people are diagnosed with ‘carcinoma in situ’, where no cancer cells have grown beyond the duct or lobule.
Most cases develop in women over the age of 50 but younger women are sometimes affected. Breast cancer can develop in men though this is rare.
Staging means how big the cancer is and whether it has spread. Stage 1 is the earliest stage and stage 4 means the cancer has spread to another part of the body.
The cancerous cells are graded from low, which means a slow growth, to high, which is fast growing. High grade cancers are more likely to come back after they have first been treated.
What causes breast cancer?
A cancerous tumour starts from one abnormal cell. The exact reason why a cell becomes cancerous is unclear. It is thought that something damages or alters certain genes in the cell. This makes the cell abnormal and multiply ‘out of control’.
Although breast cancer can develop for no apparent reason, there are some risk factors that can increase the chance of developing breast cancer, such as genetics.
What are the symptoms of breast cancer?
The usual first symptom is a painless lump in the breast, although most breast lumps are not cancerous and are fluid filled cysts, which are benign.
The first place that breast cancer usually spreads to is the lymph nodes in the armpit. If this occurs you will develop a swelling or lump in an armpit.
How is breast cancer diagnosed?
- Initial assessment: A doctor examines the breasts and armpits. They may do tests such as a mammography, a special x-ray of the breast tissue which can indicate the possibility of tumours.
- Biopsy: A biopsy is when a small sample of tissue is removed from a part of the body. The sample is then examined under the microscope to look for abnormal cells. The sample can confirm or rule out cancer.
If you are confirmed to have breast cancer, further tests may be needed to assess if it has spread. For example, blood tests, an ultrasound scan of the liver or a chest x-ray.
How is breast cancer treated?
Treatment options which may be considered include surgery, chemotherapy, radiotherapy and hormone treatment. Often a combination of two or more of these treatments are used.
- Surgery: Breast-conserving surgery or the removal of the affected breast depending on the size of the tumour.
- Radiotherapy: A treatment which uses high energy beams of radiation focussed on cancerous tissue. This kills cancer cells, or stops cancer cells from multiplying. It is mainly used in addition to surgery.
- Chemotherapy: A treatment of cancer by using anti-cancer drugs which kill cancer cells, or stop them from multiplying
- Hormone treatments: Some types of breast cancer are affected by the ‘female’ hormone oestrogen, which can stimulate the cancer cells to divide and multiply. Treatments which reduce the level of these hormones, or prevent them from working, are commonly used in people with breast cancer.
How successful is treatment?
The outlook is best in those who are diagnosed when the cancer is still small, and has not spread. Surgical removal of a tumour in an early stage may then give a good chance of cure.
The routine mammography offered to women between the ages of 50 and 70 mean more breast cancers are being diagnosed and treated at an early stage.
For more information visit breastcancercare.org.uk or www.cancerhelp.org.uk
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