Circadian biology explains why heartburn is common at night. Credit: Nancy R. Gough, BioSerendipity

I have known many people, including my own mother, who suffered from heartburn or gastro-esophageal reflux disease (GERD). Frequently, they complain of pain at night and wonder why they would have pain at night when they are not eating. The simple answer is that there is a surge of acid production by the stomach that occurs every night. This seems counterintuitive, but makes sense if you consider that nearly all aspects of physiology exhibit daily rhythms (referred to as circadian rhythms).

Aspects of human physiology exhibiting a circadian rhythm. By Yassine Mrabet, Addicted04, CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons. Read more

These circadian rhythms are controlled by a “master clock” or set of neurons in the brain that is controlled by light signals, as well as “clocks” in the periphery. These clocks are controlled by gene expression cycles that regulate protein production.

The parasympathetic nervous system is the part of the nervous system that promotes energy conservation, food and nutrient absorption, and other “rest and digest” functions. This part of the nervous system is controlled by the circadian clock in the brain and is active during the night. Thus, in addition to the signals generated by eating, this nightly activity of the parasympathetic nervous system can trigger episodes of heartburn or acid reflux. Indeed, for those suffering from frequent nightly heartburn or GERD may find that taking the acid-blocking medication in the evening with dinner rather than in the morning is often most effective.

Further Reading

B. V. Vaugh, S. Rotolo, H. L. Roth, Circadian rhythm and sleep influences on digestive physiology and disorders. ChronoPhysiology and Therapy 4 (September 2014) DOI: 10.2147/ctps448061. Full Text

K. Eckel-Mahan, P. Sassone-Corsi, Metabolism and the circadian clock converge. Phys. Rev. 93, 107–135 (2013). PubMed

Cite as: N. R. Gough, Why heartburn is common at night. Medium (20 August 2019).