Monthly Archives: September 2017

Harvard study strengthens link between breast cancer risk and light exposure at night

Harvard study strengthens link between breast cancer risk and light exposure at night

August 18, 2017 7.36pm SAST Updated August 21, 2017 6.16pm SAST

A new study from Harvard has found greater risk of breast cancer in women who live in neighborhoods that have higher levels of outdoor light during the night.

The findings are based on the Nurses’ Health Study (NHS), which has for decades been advancing our understanding of risks to women’s health.

For this study, epidemiologist Peter James and colleagues followed nurses in the NHS for breast cancer occurrence from 1989 to 2013. The home of each of 109,672 nurses was geocoded, and the average light level in the immediate neighborhood at night was estimated from satellite images taken by the Defense Meteorological Satellite Program. These estimates were updated over the 15-year follow-up period. By 2013, a total of 3,549 new cases of breast cancer had been diagnosed, about what’s expected among this number of women.

The study found a direct relationship between a woman’s neighborhood nighttime light level before diagnosis and her later risk of developing breast cancer: The higher the light level, the higher the risk. These findings held even when taking into account many other factors that may also affect risk such as age, number of children, weight, use of hormone medications and a long list of additional potential confounders.

Of importance if confirmed in more studies, the relationship was strongest in young women diagnosed before menopause. James also conducted many further subgroup analyses after the primary objective of the study had been verified; these subgroup findings may or not be seen in future studies. Two that stood out are that the association was confined to current and former smokers, and nurses with a history of night work.

The study is significant because it adds a strong piece of evidence to the growing body of studies supporting the idea that excessive electric light exposure at night increases a woman’s risk of breast cancer.

Why was the study done?

The idea that electric light at night (LAN) might explain a portion of the breast cancer pandemic dates back to 1987. It was pretty far-fetched at the time because light doesn’t seem toxic in any way that could cause cancer. It can’t break chemical bonds and damage DNA, and it’s not a hormone like estrogen, which, in excess, can cause changes in the breast that can lead to cancer. Light is, by definition, the visible part of the electromagnetic spectrum, and so it does not include X-rays or even ultraviolet radiation, which can burn skin.

Light is an exposure that challenges the conventional definition of a toxic substance. If a little asbestos is bad for you, more is certainly worse. The same holds for ionizing radiation (like X-rays), dioxin and lead.

The difference is that the effects of exposure to light on human health depend crucially on timing. Over millions of years, we have evolved with a daily cycle of about 12 hours of bright light (the sun) and about 12 hours of dark. So during the day, our body expects light, whereas during the night it expects dark. There is a deep biology to this, and electric light is throwing it out of kilter.

One perplexing possible consequence of this light exposure is an increased risk of breast cancer in women. Researchers, including me, have been exploring this possible link in part because breast cancer has no single known major cause. This is unlike many of the other common cancers such as lung, liver, cervix and stomach, for which a major cause has been identified for each; these major causes are, respectively, smoking, hepatitis viruses, human papilloma virus and the bacterium Helicobacter pylori.


But how could the nighttime light level outside a woman’s home in her neighborhood affect her risk of breast cancer?

The rationale for studying the outside light level is the assumption that communities that shine brightly to a satellite at night are composed of people who in general are bathed in LAN: They have greater exposure in their home, outside on the street, and for evening entertainment in the city. So, the satellite data are thought to be a surrogate, or a proxy, for this actual LAN exposure to each woman, particularly in the evening before sleep.

Blue light is more likely to delay the body’s transition to nighttime physiology and the natural rise in melatonin, which has been shown in rats to have a strong anti-cancer effect. Shutterstock

Too much evening light can delay the normal transition to nighttime physiology that should begin at dusk. An important part of this transition is a substantial rise in the hormone melatonin in the blood. Melatonin has been shown to have strong anti-cancer effects in lab rats. The shorter the wavelength of the light – that is, light that has more blue relative to other colors – the greater impact on lowering melatonin and delaying transition to nighttime physiology.

My colleagues and I did a similar analysis using satellite data in the state of Connecticut. We also found a stronger effect in younger women, as did another study from 2014 conducted among teachers in California. The studies from Harvard and from California are superior to ours because they both had individual-level data on many more potential confounders than just age, which we did not. Yet all three studies do point in the same direction.

Two concerns

The estimate of elevated risk of breast cancer in the new Harvard study is modest, at only 14 percent for the most highly lit neighborhoods, compared to the least.

If true, it would still account for many cases. However, there are two concerns about this estimate’s validity, which are actually opposites of each other.

On the one hand, the apparently elevated risk may be due to other factors that go along with more highly lit neighborhoods, and the LAN actually has no impact. This is called confounding. The Harvard study is one of the best-equipped studies ever conducted of women’s health to deal with this possibility because it has individual-level data on so many characteristics recorded for each subject, such as age, weight, smoking, body mass index, income and on and on.

The researchers included these factors into their statistical models, and it did not change their estimate of the effect for LAN on breast cancer risk. However, the information on these other factors is not perfect, and there may still have been some of what is called “residual confounding.”

On the other side, if evening and late-night electric light exposure actually does increase a woman’s risk of breast cancer, then this estimate of 14 percent probably understates the true effect, and maybe by a lot.

The reason is that the estimate of LAN exposure from the satellite images is only a surrogate for the light that would actually matter, which is each woman’s individual exposure to light in her eyes during the evening and night whether she is home or out and about.

Another limitation of epidemiological studies, like the Harvard one, is an effect known as exposure misclassification, which tends to underestimate the level of health risk when using a surrogate to measure the real exposure.

In this case, the satellite images act as a surrogate for actual nighttime light exposure to each woman. The poorer the surrogate (satellite images) is correlated with the actual exposure (light to eyes of women at night), the lower the estimate of risk will be from an epidemiological study that uses that surrogate. And it is unclear how accurate a stand-in these satellite images are for actual light exposure to each individual woman.

A modern marvel turned urban blight

The Harvard study comes closely on the heels of a very public warning from the American Medical Association on potential health problems from “white” LED street lights. It is important to note that the nighttime light levels used in this new study were recorded before any widespread use of “white” LED street lighting.

If the results from Harvard are real, and too much light at night from any and all sources does increase a woman’s risk of breast cancer, then retrofitting street lighting all across America should be done in a way that does not further contribute to the problem. It would be best to select luminaires that are as dim as possible, and weak in the short wavelengths (e.g., blue), yet still consistent with accomplishing their intended purpose.

Electric light is one of the signature inventions of an inventive species. But its overuse has caused an obliteration of night in much of the modern world. The loss of night has consequences for all forms of life, including us. And the mounting evidence for a connection to breast cancer is alarming.

This article was updated on August 21 to indicate that the association between light level and risk of breast cancer was found in current and former smokers and nurses with a history of night work

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Medicine for older people is the same for anyone else: treat the person, not just the body


Medicine for older people is the same for anyone else: treat the person, not just the body

January 23, 2017 6.10am AEDT

In the 16th century, French philosopher Rene Descartes moved the body from the sacred to the profane by separating it from the mind. The body thus became a proper object of study by the emerging natural sciences. From anatomy flowed physiology and the birth of what we know as modern medicine. The model of the body as a machine which can be broken and therefore fixed has had great success, unimaginable only 100 years ago.

The problems with this model seem well understood, and are best explained in a landmark paper on suffering in medicine written 30 years ago. It points out bodies cannot suffer, only persons. A model with the body at the centre, focusing on the disease and how to get rid of it, fails to respond to the suffering of the person. Modern clinicians in this model do not see suffering as it is. We are merely the mechanics that fix the broken machine that is your body.

While this is admittedly a bleak, generalised view of modern medicine and some specialities such as general practice, geriatrics and palliative medicine do transcend this model, my experiences of hospital-based medicine give me reason to examine its effects.

I have always assumed older people were just like me, except older. As time goes on, fewer are older and more are younger. We all want the same things. Long productive lives, fulfilling relationships and to be able to do things. It is only as we age that we begin to understand the value of independence. It is invisible to the well and young.

Palliative medicine has shown me that people value their independence more than their lives. While discussions about death are often met with stoic indifference, rarely do people facing loss of independence remain unmoved.

Medical intervention in older people has the same aims as that in younger people. To cure, maintain or comfort. Being older just means you are more likely to have diseases already. Unfortunately, one of these diseases is frailty. Frailty is becoming increasingly recognised as its own entity. Currently there is no cure for frailty and ageing, as its cause cannot be prevented.

To be frail means you are much more likely to need help to do things. You are more likely to have a chronic disease and you are less likely to survive a serious disease. It also means the part about cure “at any cost” can have quite a cost. The burden of the treatment can outweigh the benefit, the risks of death or disability loom.

The adage of ‘curing at any cost’ can have a significant cost in older patients. Screenshot, Youtube

An ethical approach to medicine requires we obtain consent for interventions we propose. Informed consent implies that accurate information about prognosis can be communicated to the patient. This has proved elusive even for blunt measures, such as whether or not someone will live.

When it comes to the likely effect on independence, estimating the risk of functional decline for an older individual facing a serious event becomes an inexact science.

The difficulties become more apparent when viewed within the idea of the body as machine and doctor as mechanic. Seeing only the body and not the person leaves me with inexact probabilities as guides.

Cure at any cost means I am unable within my own mind to comprehend the effect on the person. The frenetic pace of the hospital environment denies me the time. Lack of life experience for a younger doctor makes many considerations invisible. Death aversion within medical culture colours consultations.

My work in a busy emergency department has taught me older people are indeed like the rest of us. They want to be seen, recognised as people and treated as adults. It’s easy to find out something about the person. They don’t want superhuman medicos. They want us to be honest and to be able to express uncertainty.

A greater part of the satisfaction I find in my work comes from helping older people confront what is in front of them, and helping them make decisions in the context of them as a person, not just the failing lumber of the body

What’s happening in our bodies as we age?


What’s happening in our bodies as we age?

January 23, 2017 6.10am AEDT

As we reach adulthood, we notice changes in our bodies at every stage of ageing. We might find we need glasses when we hit our thirties, we can’t keep weight off as easily into our forties, we mightn’t feel as strong playing sport with the kids in our fifties, and we can’t hear a conversation across a crowded dinner table in our sixties.

All of these occur because the cells and processes in our bodies have existed for longer and longer periods of time. There are many theories as to why our body ages, but two main explanations are that the DNA within our genes determine how long we will live; the other is that over time, our body and DNA are damaged until they can no longer function as before, often referred to as “wear and tear”.

The ageing brain

As we age, the volume of the brain declines. There are many explanations for this, including cell death, in which the brain cells’ structure declines over time.

Although the precise reasons for the decline in brain volume remain unclear, some research indicates it may be due to hormone levels, and wear and tear.

Some also believe that the volume of blood reaching the brain decreases due to conditions within the blood vessels and associated systems. However, this doesn’t have a great impact on a person’s ability to remember, as the brain has the ability to compensate for these changes.

You may have heard of neuroplasticity. This is the term used to explain how the brain can rewire itself by creating new pathways within the nerve cells to compensate for damage to an area. These new pathways are created when new experiences occur. So doing crosswords all of your life won’t increase the number of pathways, but if you add a new activity that you need to learn and practise, then new pathways can form.

While the risk of dementia increases with age due to many of the hundreds of causes being more present as we age, it is not a normal part of the ageing process. It is a result of damage to the brain. The reason why it is more likely to occur as we age is simply because the longer we live, the longer we expose ourselves to possible damage to the body through disease or injury, which are the main causes of dementia.

Doing crosswords in old age will only improve brain function if it’s a new activity. from

Alzheimer’s Disease, the most common cause of dementia in Australia, occurs when there is plaque build-up in the brain. This is as a result of protein build-up over time that inevitably causes tangles in the neurons (brain cells).

Changes in muscle strength

As we age, there’s a decrease in the amount and strength of muscle tissue, due mostly to the influence of decreasing hormones. To make up for the muscle mass lost during each day of strict bed rest, older people may need to exercise for up to two weeks.

However, additional decreases in muscle occur due to a decrease in activity, not just as part of the normal ageing process.

Decrease in bone density

As the body ages it absorbs less calcium from food, a vital mineral for bone strength. At the same time, changes in hormone levels affect the density of the bones.

Ageing people also often spend less time in the sun, thereby reducing their Vitamin D intake. This in turn reduces calcium absorption.

It is important people continue to exercise as they age. Exercise will not only help to maintain muscle strength, but also assist in combatting the decrease in bone density that occurs as the body ages, thereby reducing the risk of falls and hip fractures.

Exercise will help to combat common fractures in old age. from

Changes to our senses

Changes that occur directly as a result of ageing include those to vision, hearing, taste and smell. Impacts of the changes in vision are usually the first things noticed, making a person feel that they are ageing.

Changes to the eye that occur as part of the ageing process include stiffening and colouring of the lens, a reduction in the number of nerve cells, and a decrease in fluid in the eye. These lead to difficulty in focusing on close objects, seeing in low light becomes more difficult, and the ability to adapt to changes in light decline.

Some people appear clumsy, as their ability to judge the distance between objects – a cup and table, for example, or the height of stairs – becomes a problem. Many people do not realise their spills and trips are occurring as a result of shifts in their vision, known as depth perception changes. Eyes can also become drier, making them feel irritated. This can be treated with lubricating drops.

Changes in hearing include changes in registering high-pitched sounds, and words may become difficult to understand. Speaking more loudly to someone in this circumstance does not help, as the pitch is the problem, not the volume. Instead speaking slightly slower and concentrating on complete words can be helpful.

Taste and smell often decrease as part of the normal ageing process, as the cells responsible decrease in number and the ability to regenerate worn out cells decreases with age. The results make food less tasty and people less likely to eat. In addition, people’s taste can change altogether, so people who loved chocolate as a young person may prefer chilli as they age.

Overall there are many changes to the body as part of the normal ageing process as well as many that occur as a result of lifestyle factors. We are not all fated to age in a negative spiral. Many lifestyle choices made earlier in life can assist us in the future. With proactive decisions and community understanding, we can look forward to adapting to a positive ageing process