Sleep: the missing link?

When I launched the Anti-Cancer Challenge I had an intuitive sense that it should include regular, restorative sleep, even though it's not a risk factor many people associate with cancer.

For one, my body has begun telling me that it isn't too happy with my irregular sleep patterns. It's not just that I feel a little tired during the day - that, I can live with. But I have noticed that I'm more prone to colds and infections during prolonged periods of sleep deprivation - when working night after night to meet a deadline, say - than when I'm getting  7+ hours of sleep a night.

Moreover, when I'm missing out on sleep repeatedly, my menstrual cycle shortens and I experience more noticeable PMS symptoms. At first I put this down to approaching menopause, but then I noticed that whenever I managed to sleep more regularly, my cycle would revert to its previous clockwork regularity.

Talking with the people around me, I gather that quite a few of us struggle to get restorative sleep. In many cases, the problem may lie with too muc exposure to artificial light, both at night and during the day.

Prior to the industrial era, humans were exposed to bright, full-spectrum sunlight during the day and to complete darkness at night, and their body clocks closely matched this natural cycle. Since the advent of electric light some 120 years ago, however, our exposure to natural light has been significantly replaced by artificial lighting. Moreover, westernized societies are 24/7 communities where many of us are being exposed to artificial light during the night both at home and particularly in the workplace, thus disrupting our natural circadian rhythms.

Exposure to light at night interferes with melatonin, a hormone involved in a multitude of bodily processes including cardiovascular function, bone metabolism, hormone balance and cancer development and growth. Melatonin is produced in the pineal gland at night, when it's completely dark. When we are exposed to light at night, however, melatonin production is suppressed and this in turn may increase cancer risk though a variety of complex mechanisms.

Studies have shown that melatonin inhibits the development and growth of experimental models of breast cancer, whereas exposure to constant light stimulates mammary tumors in laboratory animals. Epidemiological studies back this up; they show that women working night shifts have a significantly elevated risk of breast, endometrial and colorectal cancer, while male night-shift workers are at a significantly increased risk of developing prostate cancer, presumably due to their increased exposure to light at night. (Read this excellent review for more details.)

Highlighting the seriousness of the problem, the World Health Organization's International Agency for Research on Cancer (IARC) concluded in 2007 that "shift work that involves circadian disruption is probably carcinogenic to humans."

But it's not just night-time exposure to light that's a problem. As a reader of my Psychology Today blog "Nourish" helpfully pointed out, nocturnal melatonin production is also strongly influenced by how much daylight we are exposed to. A Japanese study found that spending one's day in dim indoor lighting leads to a weaker increase in melatonin levels at night than being exposed to bright outdoor sunlight. Thus not only shift-workers, but anyone leading an indoor and in-car lifestyle, like me, may be affected.

On the other hand, sleep duration - number of hours slept - is less clearly linked to cancer risk; indeed, epidemiological investigations have yielded ccnflicting results. While a Finnish study indicated that women sleeping 9 hours a night or longer were 31% less likely to develop breast cancer than women reporting 7-8 hours of sleep per night, a British study found no significant difference in the breast cancer risk of those sleeping 9 hours or more and those getting less sleep, and a third study actually detected a small increase in the breast cancer risk among women reporting more than 9 hours of sleep.

Conventional wisdom holds that 8 hours of sleep are "normally" required for optimal rest, but not all experts agree. "The fixation on sleep duration is unhelpful," comments Kevin Morgan, Professor of Gerontology at Loughborough University. "Sleep needs vary enormously from one person to another." As he sees it, the best criterion to measure sufficient sleep is "whether we feel restored by our sleep and are able to do what we need to do throughout the day." Age and gender also influence how much sleep we need, he says, making it impossible to set a "correct" number of hours people should sleep each night.

So where does all this leave people like me, who are not exactly shift workers but do spend a large portion of their nocturnal hours bathed in artificial light? David Blask of the Tulane University School of Medicine, New Orleans, speculates that non-shift working individuals who are not melatonin-deficient but who are chronically sleep-disturbed or deprived for other reasons may be at greater risk of developing cancer "due to the independent effects of immune suppression induced by sleep deprivation," though he notes that this hypothesis needs to be tested through more research.

What does this mean for my sleep challenge? I am still piecing together the puzzle, but initial conclusions are emerging. One is that sleep disruption and night-time work may have a negative effect on my immune system and overall hormone balance - as witnessed by the symptoms described above. In addition, daytime exposure to full-spectrum light is something I should increase from current near-inexistent levels. (Lighter, warmer spring and summer weather should help.)  I don't plan to sunbathe - another cancer risk! - but exercising outdoors rather than in my living room would be a good place to start.

Moreover, sleeping in a fully darkened bedroom should help stimulate melatonin production. And while sleep duration may not be directly relevant, I will try to increase mine a little for I do not currently meet Professor Morgan's criterion of feeling "restored and able to do what I need to do throughout the day."

Taming the night owl: my sleep challenge

I love the night – always have done!

As a child, I would read under my duvet for hours with a flash light. In the dark, ideas seemed to flow more freely, allowing me to travel strange and wondrous worlds inaccessible during daytime hours.

In my teens, staying up late seemed sophisticated and grown-up. One time, my father (a fellow night-owl) found me at 1 a.m. penning a school essay on the topic of “Existentialism”. He sat down next to me on the edge of my bed and we talked about The Meaning of Life until 3 a.m. How cool was that!?

Throughout my youth, I would cheerfully ignore my mother’s tedious admonitions: “sleep is the best medicine” (boring!), “every hour of sleep before midnight is worth two after” (phooey!), or “early to bed, early to rise makes you healthy, wealthy and wise” (yeah, whatever). She would retire at 10 p.m. every night to get her 8 hours’ shut-eye while Dad and I watched old Westerns on television.

Over the years, my nocturnal life took on new and increasingly exhausting forms: student parties and late-night exam revision, burning the midnight oil to catch up on chores after long workdays in the office, or arguing with my husband. (In our early years of marriage, whenever we reached a certain level of fatigue almost anything could trigger a fight. We dubbed these our “eleven-o’clock-fights” as they always seemed to take place after that time. Eventually we banned potentially inflammatory topics between the hours of 11 p.m. and 7 a.m.)

And finally, the ultimate sleep-killer: motherhood and on-demand breastfeeding. Baby Number One – a fitful sleeper who rarely snoozed more than two consecutive hours for the first year – transformed me into a moody mess.

Babies Two and Three – delivered in a convenient double-pack – turned me into a sleep-deprived wreck. Yet, by the time they weaned themselves at 10 months, I had become so used to the chronic fatigue that I couldn’t remember what it felt like to be rested, alert and fresh, and so no longer missed it. I soldiered on in a daze, hoping fervently that coffee and anti-wrinkle-cream could compensate for my 5-hour-a-night sleep habit.

Eight years later, I still love the night. When the daytime hurly-burly of school runs, work deadlines, grocery shopping, meal preparation and dish-drying lies behind me and the last child has gone to bed, I feel the night beckoning me to explore the many temptations she has to offer: perhaps a few emails to friends, some pages in a good book, a spot of internet surfing, maybe a late-night recipe-test-run? The possibilities are endless, as is the wide-open mental space. No telephones, no doorbells and no squabbling children can disturb me now – I am at one with the night.

When he’s home, my husband – a sensible early-bird like my mother – marches me off to bed at 10.15 p.m. to make sure I get enough sleep. (I fondly call him the “Sleep Police”.) But when he’s away travelling for work, about three to four days most weeks, I go back to my nocturnal perambulations.

However, all good things come to an end, and my varied and stimulating nocturnal life is one of these – for sleeping as little as five to six hours a night is taking its toll. My mother, at 72, has fewer wrinkles than me; I am forgetful and often too tired to exercise; and thoughts of stimulating foods – such as chocolate, bread and dried fruit – are never far from my mind (or my waistline).

It wasn’t until I wrote my anti-cancer nutrition guide (mostly between the hours of 9 p.m. and 2 a.m....) that the importance of regular sleep really hit home. Not just because I needed to be rested in order to be creative, but also because I discovered that lack of sleep has a direct bearing on cancer.

The exact link between cancer and sleep is not clearly understood, but epidemiological research suggests that night-time shift workers have a higher risk of cancer than those who get their regular seven to eight hours of shut-eye. (More on this in my next post.) While I'm no shift worker, I do spend a lot of nocturnal waking time in front of a computer screen and hardly ever get 7 hours of uninterrupted sleep.

Giving up two to three hours of productive alone-time each day may be the hardest part of my Anti-Cancer Challenge. Yet, if I am to remain productive and healthy over the long term, I need get regular doses of high-quality sleep. This week I will describe how I plan to do this. Meanwhile, do tell me how you manage to fit healthy sleep habits into your busy lives!

The triad of health - a virtuous cycle

The Anti-Cancer Challenge is based on a “triad of health” consisting of optimum nutrition, daily exercise and adequate sleep and rest. For while we may be healthy enough when incorporating only one of these elements in our lives, I don't think it is possible to attain optimum health unless we practice all three.

If all goes according to plan, each of these three cornerstones will reinforce the other two, as depicted in my modest graphic (left and below). My fervent hope is that if I can stick with it for a year, I will continue doing so for the rest of my life.

There really is no alternative. For two years now, I have been burning the candle at both ends, over-extending myself in my job while at the same time trying to be a dedicated mother-of-three, wife and homemaker. “This is just a temporary bottle-neck,” I kept telling myself. “Things will slow down soon and then I’ll get my life back.” But as month after exhausting month passed, this looked increasingly unlikely.

The first healthy habit to go overboard was sleep as I burned the midnight oil to keep up with e-mails, research and paperwork. The next casualty was exercise – for how could I exert myself physically when I was struggling just to keep my eyes open? Then even my diet started slipping: my morning coffee was getting a little stronger every month, and I was snacking on dried fruit and other sweet snacks throughout the day to boost my flagging energy levels. What little sleep I allowed myself was fitful, disrupted by my high-energy snack-habits and too much time spent in front of the computer.

During previous periods of stress, I often came down with sinus infections or digestive problems and my hormone cycle would go loopy. Ten years ago, when I was particularly overstretched for a prolonged period of time, I had to be treated for cervical carcinoma in situ. Each time I fell ill, I would swear that I’d change my ways; but once I had regained my strength I would go back to pillaging my reserves.

This time, though, I have decided not to wait until disaster strikes. At 44 I am fit enough to put healthy habits in place with relative ease, yet mature enough to stick with them (one hopes!). If I don’t take the time to look after myself now, I’ll have to spend that time in years to come in doctors’ and physiotherapists’ waiting rooms – a prospect I don’t relish.

Under the soon-to-be-published guidelines of the Anti-Cancer Challenge, more sleep will provide the energy to exercise, while exercising more will help me to sleep better. Better sleep will also allow me to reduce my sugar and caffeine consumption, again reinforcing sounder sleep! I have also noticed that when I exercise, I automatically seek out healthy foods – vegetables, fruits, lean protein – and don’t feel the slightest bit drawn to sugar or chocolate and the illusion of energy they offer. And when I eat an optimal diet I have the energy I need to exercise and cope with the demands of my busy life. A virtuous cycle!

It’s hardly rocket science, but I have summarized this virtuous cycle in a diagram (below; click on graphic for a more legible enlargement) which I have printed out and stuck on my refrigerator to remind me to look after myself.