Why pain spikes at night, Here is what you need to know

HEFEI, March 23: Many people with chronic pain find their discomfort manageable during the day but unbearable at night, and a team from China has now uncovered the neural mechanism behind these daily fluctuations. The study, led by Zhang Zhi of the University of Science and Technology of China in eastern Anhui province, was published on Friday in the journal Science.

While the circadian rhythm of pain is a known biological pattern -- typically weaker during activity and stronger at rest -- the underlying mechanism was unclear. The brain’s master clock, the suprachiasmatic nucleus (SCN) in the hypothalamus, was known to regulate sleep and hormones, but its direct link to pain was missing. Using advanced viral tracing technology, the team mapped a specific neural pathway in mice that connects the SCN to the spinal cord. The researchers found that neurons in this pathway are controlled by the SCN’s daily rhythm. Since mice are nocturnal, their activity cycle is opposite to that of humans. During the mice’s rest period (daytime), the SCN was highly active, driving this circuit to amplify pain signals in the spinal cord. At night, when the mice were active, SCN activity dropped, naturally reducing the intensity of pain signals transmitted through the spinal cord.

“This discovery explains why pain sensitivity follows a daily rhythm,” Zhang Zhi explained, adding that it also provides a new theoretical basis for improving clinical pain management by aligning treatment schedules with the body’s natural biological clock. Separately, just a few years ago, only a handful of patients would walk into the sleep clinic at Huimin County People’s Hospital in Binzhou, east China’s Shandong Province. Today, that number has tripled, with annual visits rising from around 200 to 600. “It’s not that suddenly more people can’t sleep,” said Yin Jianfeng, the clinic director. “It’s that more people are willing to come for help.”

The rising footfall reflects both the widespread nature of sleep problems in China and the rising public awareness of sleep health -- a challenge brought into focus as the country marks World Sleep Day on Saturday. According to a survey published in 2025, Chinese people aged 18 and above sleep an average of 7.06 to 7.18 hours, while 48.5 percent report experiencing sleep problems, a share that rises with age. The survey, conducted by the Chinese Sleep Research Society and the Chinese Center for Disease Control and Prevention, showed that on average, Chinese adults fall asleep at 11:15 p.m. and wake at 6:38 a.m. Among younger people, late sleep has become the norm, with around half not falling asleep until after midnight. High-pressure professionals, people with chronic illnesses, and those with mental health conditions are among the groups most at risk of insomnia.

Huang Zhili, a professor at Fudan University and chairman of the Chinese Sleep Research Society, pointed out that the rise in insomnia is closely linked to China’s rapid industrial and digital development, which has brought intensified competition, heavier workloads, and a growing reliance on electronic devices. Excessive screen use can disrupt sleep through light and noise stimulation, while constant exposure to information may also heighten anxiety.(Xinhua)