Artificial Light and Circadian Rhythm – Are We Messing It Up?

Artificial Light and Circadian Rhythm

The continuous exposure to light in mice induced a progressive loss of trabecular bone similar to that observed in early age-related osteoporosis, and an increased thickness of cortical bone consistent with an accelerated effect of ageing. Up to 21% of elderly adults have osteoporosis and some of these changes have actually been reported in shift workers: studies have shown that female shift workers have an increased risk of bone fractures and decreased bone mineral density.

Continuous exposure to light also induces a heightened pro-inflammatory state. Upon an immune stimulus, mice exposed to continuous light showed an increased production of pro-inflammatory molecules and a decreased secretion of anti-inflammatory compounds, even though this effect was transient.

This intensified pro-inflammatory state is also observed during aging. Furthermore, human studies have also shown that shift workers have an increased risk of cancer and metabolic syndrome associated with immune system dysfunction, which is also known to aggravate age-related pathologies.

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The reduction in rhythmicity in the SCN of mice continuously exposed to light also matches rhythm changes that occur in aged individuals. In fact, recent research suggests that impairments in the circadian clock within the SCN may be a defining factor in ageing, being likely that an aged circadian system may actually contribute to the age-related decline in health.

This study solidified the notion that long-term exposure to continuous light can have a significant impact on health. Interestingly, most of the health parameters measured quickly returned to normal after restoring a regular light-dark cycle. Nevertheless, it becomes clear that exposure to artificial light is not at all harmless.

By messing with our circadian rhythms through constant exposure to light, we may be accelerating our ageing process and be actively weakening our health and resistance to disease.

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References

  • Lucassen EA, et al (2016). Environmental 24-hr Cycles Are Essential for Health. Curr Biol, 26(14):1843-53. doi: 10.1016/j.cub.2016.05.038
  • Michaud M, et al (2013). Proinflammatory cytokines, aging, and age-related diseases. J Am Med Dir Assoc, 14(12):877-82. doi: 10.1016/j.jamda.2013.05.009
  • Nakamura TJ, et al (2016). The suprachiasmatic nucleus: age-related decline in biological rhythms. J Physiol Sci, 66(5):367-74. doi: 10.1007/s12576-016-0439-2
  • Quevedo I, Zuniga AM (2010). Low bone mineral density in rotating-shift workers. J Clin Densitom, 13(4):467-9. doi: 10.1016/j.jocd.2010.07.004
  • Stevens RG, et al (2014). Breast cancer and circadian disruption from electric lighting in the modern world. CA Cancer J Clin, 64(3):207-18. doi: 10.3322/caac.21218
  • Wang XS, et al (2011). Shift work and chronic disease: the epidemiological evidence. Occup Med (Lond), 61(2):78-89. doi: 10.1093/occmed/kqr001

Written by : Sara Adaes, PhD 
Originally appeared on: Brainblogger.com
Republished with permission.

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