Is shift work a risk factor for type 2 diabetes?

Type 2 diabetes rates are on the up, and there is real concern within the medical community that we are seeing something of a ‘diabesity’ epidemic that has considerable personal and social consequences. The usual focus regarding the prevention of type 2 diabetes is ‘diet and exercise’. But, other less well-recognised factors appear to influence diabetes risk, and one of these is sleep.

I was interested to see a recently published study which links shift work with an increased risk of type 2 diabetes, and this association was particularly strong in men [1]. This study cannot be used to conclude that shift work somehow causes diabetes (only that they are associated). The same is true of studies which have linked short-sleep with an increased risk of diabetes [2].

However, there is some evidence that short sleep has the potential to impair blood sugar control (glycaemic control).

In one study, nine healthy adults were tested to see what effect sleep deprivation has on insulin resistance [3]. On one night, individuals were allowed to sleep for up to 8.5 hours (23.00 – 7.30 hrs). On another night, sleep was only permitted for four hours (01.00 – 05.00 hrs). The actual average sleep times were 7 hours 34 minutes and 3 hours 46 minutes respectively.

The results showed that in the sleep-deprived state there was evidence of insulin resistance. ‘Endogenous’ sugar production (internal production of sugar, say, from the liver) was higher, and clearance of glucose (say, into muscle cells) was lower in the sleep-deprived state.

Now, less than four hours sleep is not much sleep. But then again, increased insulin resistance was seen in individuals after just one night of sleep deprivation. It’s possible that less extreme sleep deprivation or sleep disruption (such as shift work) over longer periods of time also poses hazards regarding diabetes risk.

In one study, the impact of ‘shift work’ on disease markers, including those for diabetes [4]. 26 healthy individuals were allowed to sleep for up to 10 hours a night for 10 nights. Then, they were restricted to no more than 5 hours sleep for 8 nights. In this setting, some individuals took their sleep at night. Others, however, simulated ‘shift work’ by taking their sleep in the day on four of the eight days.

Short sleep led to a reduction in insulin sensitivity (as has been noted in previous studies), as well as an increase in markers of inflammation. Also, in men, reductions in insulin sensitivity and increases in inflammation were about twice a bad when they were sleeping in the ‘shift’ setting, compared to those sleeping normally (at night).

The evidence as it stands supports the idea that both duration and pattern of sleep can have a bearing on risk of type 2 diabetes, and other chronic health issues too.


1. Gan Y, et al. Shift work and diabetes mellitus: a meta-analysis of observational studies Occup Environ Med doi:10.1136/oemed-2014-102150

2. Chaput JP, et al. Sleep duration as a risk factor for the development of type 2 diabetes or impaired glucose tolerance: Analyses of the Quebec Family Study. Sleep Med. 2009;10(8):919-24

3. Donga E, et al. A single night of partial sleep deprivation induces insulin resistance in multiple metabolic pathways in healthy subjects. J Clin Endocrinol Metab. 2010;95(6):2963-8

4. Leproult R, et al., Circadian misalignment augments markers of insulin resistance and inflammation, independently of sleep loss. Diabetes. 2014;63(6):1860-9

13 Responses to Is shift work a risk factor for type 2 diabetes?

  1. Zara Pradyer 25 July 2014 at 7:59 pm #

    I have no wish to detract from the main point but I wonder if shift work might also imply that the worker has less opportunity for exposure to sunlight and hence might be more vulnerable to the very common condition of being deficient in Vitamin D and hence more prone to diabetes.

    • Michele Mercurio 26 July 2014 at 10:43 am #

      VERY good point, and I’ve never seen it mentioned in any of the studies that look at weight and shift work.

  2. Michele Mercurio 25 July 2014 at 8:47 pm #

    What is the research showing currently on obesity/diabetes rates among RNs? I know that historically the profession has had a very high obesity rate that was at least partially attributed to sleep deprivation/disrupted sleep cycles, at least among nurses who work rotating shifts (2 weeks of days, one week of nights, etc). I note anecdotally, however, that nurses as a whole (in any setting/on any schedule) tend to be overweight; some almost to the point of immobility, which is odd as it is very few of them who have desk/admin positions.

  3. sten 25 July 2014 at 8:55 pm #

    Longer good sleep = longer fast which translates into longer periods with low blood sugar, or periods where blood sugar can be allowed to fall lower, which would also allow insulin to drop, hereby directly increasing insulin sensitivity. Even if no food (sandwiches often for shift workers?) was consumed in the awaked spells, the ready-ness through awakening increases blood sugar, so in my book I find the findings to be reasonable and sound!.

    Longer (good) sleep periods would allow low blood sugar for longer time and hence less insulin in proportion which also means longer cleansing time for blood vessel plack and hence improved heart health, In part from what I read about how blood sugar needs to go down below 5 to reduce arterial plaque at Dr William Davis site. Trackyourplaque.

    Same would of course apply to the apparent sticky culprits, the sugar coated or glycated (small) LDL. Is it easy to measure these villains? Or is a sufficiently low HbA1c level ok to know that few of them are at large? And if yes, what HbA1c level is required and what maximum% carbs can be recommended to stay there?
    Of course the maximum permissible carb % drops with increasing age, but say for an average 40-50 year old ?

  4. Louis Farrakhan 25 July 2014 at 9:15 pm #

    shift work messes up a person’s eating habits & would be a contributing factor.

  5. Kerin 26 July 2014 at 6:42 am #

    There is no doubt that shift work has affected my BSL. I eat low carb – no sugar, have followed your recommended way of eating for 18 months. I work two 12 hour days, followed by two 12 hour nights (I’m an ambo in Australia), it’s extremely busy. It is difficult to get enough sleep between the day and night shift, and caffeine is often the drink that I resort to during the night. My BSL pre and post prandial seems to be fairly stable, never high or low, but my fasting glucose level is generally always borderline high (5.9 mmol) even on my days off. I find it impossible to lose weight and guess that I am insulin resistant, even though I am an extremely healthy eater. I would love to see more studies done on shift work. Lack of sleep has a lot to answer for………….

    p.s. Love your ‘A Great Day at the Office’

  6. Vanessa 26 July 2014 at 7:20 am #

    Someone beat me to it! When I heard this on the news, my immediate thought was the possibility of vitamin D deficiency. Was this measured in the study participants?

    • sten 26 July 2014 at 8:19 am #

      Guess they did not control for vitamin D. But although sunshine is a key source, our skins ability to make vitamin D declines with age making D one of the few vitamins supplements that could be needed. Another few reasons for increasing D-deficiency today are:
      1/ Too many animals we eat are reared inside out o sun these days, (on wrong foods!)
      2/ A low fat diet avoids the fat in animals where the important winter- D used to be stored. 3/ People eating cholesterol lowering sterols reduce the vital cholesterol that is needed for conversion to Vitamin D…
      4/ We usually don’t reduce weight in winter any more so the summer D stays in our fat….

      Finally re LDL: Since only glycated LDL sticks in arteries it means that avoiding high blood sugar spikes from modern fast carbs (breakfst cereal and sandwiches sticks out a mile….), reduces daily glycation and preserves useful LDL for brain, heart, Vitamin D-conversion, and more that it was made for.
      By tackling root causes a lot of today’s medication can become redundant and with every one usually goes unwanted side effects.

  7. Soul 26 July 2014 at 11:19 am #

    Interesting about shift work and sleep being possibly related to diabetes too.

    Something else that I’ve read of late being possibly connected to bringing about diabetes concerns high electrical EMF fields. The EMF diabetes connection I read was observational in scope, so not proof. It caught my attention though due to my grandfather. I had a relatively thin grandfather that developed diabetes. He eventually passed away from complication due to the disease. According to my father he lived most of his life pretty much under a power line. He also complained of muscle pains, particularly in the back, which I guess is thought to be another possible problem for some with high EMF fields. Of course hard to say what brought about granddad’s conditions.

    Going further out on a limb with this, but my grandmother that lived in the house near the power line later developed Alzheimer’s disease. Her mother, that lived on the same small farm, and close to the power line too, also developed Alzheimer’s. So far they have been the only two family members that developed this disease in the family. I only mention as I’ve read some write Alzheimer’s develops from a 3rd type of diabetes, one that effects the mind. Of course speculation on this, but has me curious.

    • David 26 July 2014 at 10:27 pm #

      It would seem that different people tolerate being overweight better.

      “A crucial point is that individuals have different levels of tolerance of fat within liver and pancreas. Only when a person has more fat than they can cope with does type 2 diabetes develop. In other words, once a person crosses their personal fat threshold, type 2 diabetes develops. Once they successfully lose weight and go below their personal fat threshold, diabetes will disappear.

      Some people can tolerate a BMI of 40 or more without getting diabetes. Others cannot tolerate a BMI of 22 without diabetes appearing, as their bodies are set to function normally at a BMI of, say 19. This is especially so in people of South Asian ethnicity.”

      Some interesting work being done at Newcastle.

  8. Emma Conroy 28 July 2014 at 9:45 am #

    This is very interesting, and indicates another factor besides Vitamin D deficiency. Having said that, Vitamin D is heavily involved in blood sugar / insulin regulation, and at least in the long term must surely be a factor in this increased risk of Diabetes. Just as it must be in the increased risk of cancer that has long been known to be suffered by shift / night time workers. Over the years, this association crops up periodically in the headlines (‘Long term shift-work can double breast cancer risk’ ‘Working the night-shift may cause colon cancer’ and so on) yet in the mainstream media the focus is always on melatonin / circadian rhythm disruption, and there is no mention of vitamin D.

  9. Stephen Rhodes 28 July 2014 at 4:04 pm #

    How much of the shift work health problem is due to the resulting sleep pattern and thus disturbance of the daytime production of heparan sulphate and night-time use of this to produce melatonin sulphate, and how much is due to a metabolism pre-weakened by chronic exposure to RoundUp ™ (or similar adjuvant assisted glyphosate weedkiller) ?

    Among many concerned about the way in which Monsanto (other biosphere destroyers are also available) has played the same game with data on safety as the statin producers and pushers [our law makers are either stupid, venal, or deliberately misinformed] is Stephanie Seneff – start at first 5 latest papers.

    This promises to be a much bigger health issue than statins since everyone is potentially chronically exposed.

  10. Lorraine 5 August 2014 at 9:12 am #

    Interesting connection between shift work, sleep and diabetes. Sleep is such an important factor for health and weight loss. It must be a harder battle for shift workers that have different shift patterns.

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