Is Catch-up Sleep After Night Shifts Enough? Study Suggests 'Melatonin Deficiency' May Impair DNA Repair

After finishing night shifts, many people try to catch up on sleep during the day. But even if sleep duration is restored, can the body’s repair mechanisms fully recover?

When working under artificial light at night, the brain’s natural secretion of melatonin—normally high in darkness—is significantly suppressed. While melatonin is commonly known for regulating sleep and jet lag, a 2025 clinical study suggests it may also play a role in the repair of oxidative DNA damage during sleep.

Dr. Yen Tso-Hua,院长 of Lianxin Clinic at Lianan Preventive Medicine, explained a 2025 randomized, double-blind, placebo-controlled trial published in Occupational and Environmental Medicine. The study recruited 40 healthy night-shift workers, primarily healthcare professionals, who worked at least two consecutive night shifts per week, with each shift lasting at least seven hours. Participants were randomly divided into two groups and underwent a four-week trial. The melatonin group took 3 mg of melatonin before bedtime, while the control group took a visually identical placebo at the same time.

To assess DNA repair activity, researchers measured urinary levels of 8-OH-dG (8-hydroxy-2'-deoxyguanosine). When DNA is attacked by free radicals, the body initiates repair mechanisms, excising damaged sections and excreting them. Thus, urinary 8-OH-dG concentration serves as an indirect biomarker for DNA repair activity.

What were the results?

The melatonin group excreted approximately 80% more 8-OH-dG during sleep than the placebo group, suggesting enhanced DNA repair activity. However, as this was a small-scale trial, further large-scale studies are needed to confirm whether melatonin truly boosts DNA repair efficiency.

Dr. Yen emphasized that from a preventive medicine perspective, night shift work may affect more than just sleep. The International Agency for Research on Cancer (IARC) has classified night shift work as Group 2A, meaning it is “probably carcinogenic to humans.” One possible mechanism is that nighttime light disrupts the pineal gland’s natural melatonin rhythm, disturbing circadian rhythms, hormone regulation, and immune function, potentially leading to metabolic imbalance.

What are the functions of melatonin?

The body’s cellular repair systems operate continuously, with some processes influenced by circadian rhythms and sleep states. Melatonin itself is a potent endogenous antioxidant that not only neutralizes free radicals but also enters the cell nucleus to regulate gene expression related to DNA repair and anti-inflammatory responses.

For night shift workers, even sleeping during the day with blackout curtains, melatonin levels often remain low. Without sufficient melatonin, the cellular repair system functions like an army without a commander, struggling to effectively manage DNA damage accumulated from sleep deprivation and oxidative stress.

Dr. Yen stressed that individuals with long-term night shifts or those required to stay up late for work should consult a physician to evaluate whether melatonin supplementation is necessary, along with appropriate timing and dosage. Self-purchasing and long-term use without medical guidance are not recommended. Additionally, daytime sleep is easily disrupted by sunlight, so bedrooms should use high-quality blackout curtains and maintain a quiet, temperature-appropriate environment.

It’s important to note that the link between melatonin and DNA repair remains in the realm of cellular and circadian rhythm research and does not imply that all night shift workers need supplementation. However, if someone continues to feel fatigued after sleep, snores, wakes repeatedly at night, or suspects sleep apnea after long-term night shifts, a comprehensive sleep assessment is recommended.

The CPC 3.0 home sleep test, which integrates cardiopulmonary coupling, nocturnal blood oxygen, and snoring analysis, can help evaluate sleep quality and nighttime hypoxia, enabling early detection of sleep-related health issues.

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