The Body’s Clock

Scientists –well, all of us- have been suspicious about the health risks of shift work for a long time now. Perhaps there is a reason buried somewhere in our genes that suggests night is for sleeping and daytime for working. Originally, no doubt, it was because it was difficult to see things in the dark and lighting, even when it became available, wasn’t very good.

But there is another reason: the Circadian Rhythm (from the Latin circa –around, and dies –day) which is often defined as physical, mental and behavioral changes that follow a roughly 24-hour cycle, responding primarily to light and darkness in an organism’s environment. The body clock, in other words. And there’s the clue: light and darkness. These are not just elements in our environment that we have come to expect, they actually have a biological meaning for us although this is, to a certain extent, entrainable. Malleable. As Wikipedia (sorry!) puts it: The rhythm can be reset by exposure to external stimuli (such as light and heat), a process called entrainment. The external stimulus used to entrain a rhythm is called the Zeitgeber, or “time giver”. But it can take a while to adjust –think of jetlag, or sleep disturbance after starting a new shift at a different time.

The body can adapt to many things, no doubt; the problems seem to arise when the pattern keeps changing. As folk wisdom attests, we are inherently creatures of habit –acquired behaviour patterns that are repeated so frequently they can become almost involuntary. As no less an observer of folkways than Samuel Johnson once said: “The chains of habit are too weak to be felt until they are too strong to be broken.” So one might ask why we –and many other animals- seem prone to develop these routines, these almost unconscious ceremonies. Is it simply a need for predictability? Or is it something deeper, something tied to our evolutionary past..?

In our evolutionary development we obviously experienced disruption of light/dark cycles –they occur as we travel through the seasons- but these are gradual and steadily progressive; shift work –especially rotational shift work- is not. And only recently has it become more obvious that there may be a price to pay. There have been several studies that have looked at this in various ways, but ‘Although epidemiological studies in shift workers and flight attendants have associated chronic circadian rhythm disturbance (CRD) with increased breast cancer risk, causal evidence for this association is lacking’ as the abstract of a paper published in Current Biology noted. I saw this in a July 2015 article in BBC News reporting on a study co-authored by Dr. Kirsten Van Dycke which suggested that the chronic need to re-entrain the circadian rhythm because of changing light/dark cycles can increase the risk for both obesity and breast cancer! Now, admittedly, the study was done on mice who were prone to develop breast cancers anyway, but when the light/dark cycles were switched over a long period of time (‘Mice prone to developing breast cancer had their body clock delayed by 12 hours every week for a year’) they developed them sooner.

Humans are obviously not mice, but it is difficult to control for possible contributing factors in the average human study: ‘Several scenarios have been proposed to contribute to the shift work-cancer connection: (1) internal desynchronization, (2) light at night (resulting in melatonin suppression), (3) sleep disruption, (4) lifestyle disturbances, and (5) decreased vitamin D levels due to lack of sunlight. The confounders inherent in human field studies are less problematic in animal studies, which are therefore a good approach to assess the causal relation between circadian disturbance and cancer.’

And the conclusion from this study? ‘Animals exposed to the weekly LD [light/dark] inversions showed a decrease in tumor suppression. In addition, these animals showed an increase in body weight. Importantly, this study provides the first experimental proof that CRD [Circadian Rhythm Disturbance] increases breast cancer development. Finally, our data suggest internal desynchronization and sleep disturbance as mechanisms linking shift work with cancer development and obesity’.

This is worrisome, to say the least. One could certainly argue that a woman with an increased risk for breast cancer –say a heditarily aquired BRCA1/2 mutation- would be best to avoid jobs involving chronic irregular body clock disturbance such as flight attendants, commercial pilots, and so on. But I’m not sure the risk is confined to that population. What about others –especially if they have additional life-style risks such as smoking, diabetes, alcohol issues?

And what about men? If –as the study suggests- a chronic body clock disruption may cause a decrease in tumour suppression, would that not suggest a similarly increased risk? The disruption also seems to have an additional risk for increased weight gain –obesity. Is the risk for type 2 diabetes therefore also increased? Clearly this is an area requiring much more research -further elucidation of the mechanisms involved and mitigation strategies at the very least. Sleep is so important –regular sleeping patterns…

I can’t help but remember the words of Shakespeare’s Macbeth talking to his wife after he has killed Duncan, the king:

Methought I heard a voice cry, “Sleep no more!

Macbeth does murder sleep”—the innocent sleep,

Sleep that knits up the raveled sleave of care,

The death of each day’s life, sore labor’s bath,

Balm of hurt minds, great nature’s second course,

Chief nourisher in life’s feast.

Art, once again, anticipating Science…


Nudging Childhood Obesity

When I was a kid, obesity was not the norm. Admittedly, this was a long time ago, and no doubt I only remember brief and highly selective snippets of the time –modified, no doubt, to serve whatever demands are required in the present. But in these unexpurgated, sketches, I have memories of labeling the occasional child in the playground as ‘fat’. Whoever it was stood out from the rest –ex gregis in the true etymological sense of the word ‘egregious’- and so through the insouciance of childhood, were forever condemned to wear the epithet like a poorly fitting sweater.

Maybe we just didn’t have enough to eat in those halcyon days of early Winnipeg; maybe the winters were too severe and the necessary clothes too heavy to allow the accumulation of excessive girth. But let’s face it, normal is what we see around us. It is parochial. It is the statistics of one box. And yet, isn’t that how we judge: by what we know? If I am obese, and my child is too, then what’s the problem? And if all his friends, and all my friends are large, then how am I to adjudicate another norm? Thin is aberrant, not fat.

I came across an interesting article in Forbes magazine reporting about a study –several studies, in fact- demonstrating the inability of parents to judge whether or not their child was overweight:

This is worrisome, to say the least -unless of course you change the definition of what weight is normal… But no matter the norm, health risks for diabetes, hypertension and cardiovascular disease generally increase with increasing BMI (Body Mass Index -which is the weight in kilograms divided by the square of the height in meters: kg/m2).

And it is difficult to rationalize the increasing prevalence of corpulence in the population as an evolutionary process. It’s hard to understand how plumpness would be of any survival benefit, or why it would be selected for in a gene pool. There exist islands of controversy in this, of course:  But I think most analyses would suggest that obesity (BMI >30 -at least in North American population studies) adversely influences health and life span. So it would make sense to attempt to correct the issue as early as possible.

As an obstetrician, I am drawn to the idea that management of pregnancy and birth weight are important. I was intrigued by a prediction model I saw reported in the BBC from 2012 suggesting the risks for subsequent obesity of a child could be predicted at birth with about 80% accuracy:  I haven’t seen much about this recently, so I don’t know how well it has stood the test of scientific scrutiny, but at least it was an interesting thesis. A start.

Recently, the Canadian Task Force on Preventive Health published an update on childhood obesity guidelines:  It contains the usual admonitions against junk food and physical inactivity, of course, but advocates some innovative strategies, I think. For example, because the circadian rhythms of teenagers have been found to differ from the adults who are teaching them, it recommended starting classes later in the morning and suggested breaks in each class. And walking to school, where feasible, as part of the exercise regime… Dr. Brian Goldman, host of CBC’s ‘White Coat, Black Art’ program, while agreeing with the guidelines, detected some downsides to the recommendations however:

The contributing factors to obesity –let alone childhood obesity- are legion: genetics, dietary habits, social milieu, parental influences, environmental conditions, Media, socioeconomic status, and peer group expectations, to name a few. None are solely responsible, but unless there are some counteracting forces –incentives- all are important. Behaviour, habits, and expectations are learned phenomena and it may be something as simple as imitation of parents or friends that starts it off and then sustains it.

When faced with uncountable opponents and overwhelming odds, how can Society possibly succeed in changing things? Well, simplistically, it needs to change attitudes. Change what the majority considers acceptable. Change the mythos. It is slowly changing the acceptability of smoking as a norm; even the legitimacy of drinking and driving is under scrutiny –not only in the courts but also in the minds of drinkers. Some things are just not seen as cool nowadays.

But, given the importance of preventing childhood obesity for the health and well-being of future generations and given the relative lack of success so far, I think we need a new (old?) approach. There is a freshly-named, although age-old practice, termed ‘Nudge Theory’. It is a euphemism that my mother would have simply called manipulation because, although cleverly disguised, that’s really what it is. Wikipedia has succinct explanation: Nudge theory (or Nudge) is a concept in behavioral science, political theory and economics which argues that positive reinforcement and indirect suggestions to try to achieve non-forced compliance can influence the motives, incentives and decision making of groups and individuals, at least as effectively – if not more effectively – than direct instruction, legislation, or enforcement. Here are two introductions –take your choice: or

Education, and early identification and treatment of those at risk of becoming obese are obviously important and desirable, but I think we need something more. Something with a proven track record, albeit in different fields. Maybe ad campaigns and directed manipulation –sorry, nudging– would be valuable adjuncts. We are media savvy nowadays, and used as a tool for change, it seems ideal. As long as we are certain of our goals, and the science is correct, I think it is an ethically acceptable approach, and one with great potential.

I did, though, run across a light-hearted, but nonetheless cautionary article about nudging in the Toronto Globe and Mail:

However, we have to take advantage of all the tools at our disposal. My mother’s manipulation was unsubtle and in my face; nudging is not. If we are going to be successful in stopping the steadily increasing tide of obesity, we need to revise expectations, and change what we accept as normal. We have to alter folkways and mores –in other words the rules that society uses to guide behavior. Nudge them, I suppose…

We need the courage to try novel approaches. There is a quote by Erasmus that is germane: A nail is driven out by another nail. Habit is overcome by habit. Okay, so let’s change them. Nudge them. No! I hate the verbal evasion. Let’s mold them.