A new study published in the journal Health Data Science in August 2025 indicates that irregular sleep schedules, known as “social jet lag,” may be more harmful to health than simply not getting enough sleep. Conducted by international researchers, the study emphasizes that maintaining consistent sleep and wake times is crucial for physical and mental well-being. Carried out in cities like São Paulo and New York, the research analyzed sleep patterns of thousands of people and found that circadian rhythm disruption increases the risk of heart disease, diabetes, and immune issues. The phenomenon, common among night shift workers and those with unstable routines, triggers inflammatory responses in the body. Neurologist Paula Vallegas from Unifesp explains that irregular sleep acts as chronic stress, affecting hormones and the immune system. The finding reinforces the importance of stable routines for well-being.
The study also challenges myths about prolonged sleep. Data show that spending over nine hours in bed does not always mean more sleep but may include periods of wakefulness, reducing rest quality.
- Impacts of irregular sleep: increased inflammation and risk of chronic diseases.
- Common factor: night shift workers and young people with erratic routines are most affected.
- Initial solution: establish fixed sleep and wake times, even on weekends.
Sleep regularity emerges as a key pillar for health, according to experts.
Why sleep regularity matters
Maintaining a fixed sleep routine aligns the circadian rhythm, the biological clock that regulates functions like body temperature, hormone release, and metabolism. When sleep schedules vary widely, the body struggles to synchronize these processes. Neurologist Laura Castro from the Vigilantes do Sono platform explains that dysregulation affects hormones like cortisol and melatonin, essential for bodily balance. A 2024 Harvard University study confirmed that people with inconsistent sleep schedules had higher rates of chronic fatigue and metabolic issues. The Health Data Science study, in turn, measured sleep schedule variability in over 5,000 participants, finding that deviations exceeding one hour daily already increase health risks.
Irregular sleep also disrupts the production of inflammatory cytokines, molecules that, in excess, damage tissues and organs. This process is linked to conditions like obesity and hypertension.
Social jet lag and its effects on the body
The term “social jet lag” describes the disruption caused by frequent changes in sleep schedules, such as sleeping late on weekends and waking early during the week. This habit, common among young people and professionals with varied shifts, disrupts the circadian rhythm.
- Increased stress: the body interprets irregularity as a threat, raising cortisol levels.
- Hormonal impact: changes in insulin and ghrelin production, linked to hunger and satiety.
- Immune system: reduced production of defense cells, increasing susceptibility to infections.
- Mental health: higher risk of anxiety and depression due to brain desynchronization.
Dr. Paula Vallegas notes that social jet lag can be as harmful as traveling across time zones. Studies indicate that night shift workers, such as nurses and drivers, face up to 30% higher chances of developing chronic diseases due to this practice.
Myths about sleep duration
The belief that sleeping over nine hours is always harmful has been questioned. Objective data from the study show that many people stay in bed for long periods but do not sleep deeply. This can include frequent awakenings or fragmented sleep, which impair bodily recovery. Laura Castro explains that feeling refreshed upon waking is an important indicator but can be misleading. Conditions like sleep apnea may mask poor rest quality.
- Prolonged sleep: not always deep rest; frequent awakenings are common.
- Sleep apnea: causes breathing pauses, reducing oxygenation and sleep quality.
- Clinical evaluation: essential to identify underlying issues like insomnia or apnea.
The recommendation is to seek a detailed clinical evaluation to assess sleep health, especially in cases of persistent fatigue.
How to improve sleep regularity
Establishing a consistent sleep routine is the main recommendation from experts. This includes maintaining fixed sleep and wake times, even on weekends. Exposure to natural light during the day also helps regulate the circadian rhythm.
- Fixed schedules: try to sleep and wake up at the same time every day.
- Natural light: at least 30 minutes of morning sunlight exposure stimulates melatonin.
- Avoid screens: blue light from phones and computers inhibits sleep hormone production.
- Suitable environment: a dark, quiet, and cool room improves rest.
A 2024 experiment by the University of São Paulo (USP) showed that participants who maintained regular sleep schedules for 30 days reported 25% less fatigue and improved energy.
Long-term health impacts
Irregular sleep doesn’t just affect immediate well-being. Longitudinal studies indicate that inconsistent sleep schedules are linked to a 20% increased risk of cardiovascular diseases and 15% in type 2 diabetes. Chronic inflammation, triggered by social jet lag stress, can also accelerate cellular aging.
The Health Data Science study revealed that individuals with sleep schedule variations exceeding two hours had elevated levels of inflammatory markers, such as C-reactive protein. These markers are linked to conditions like atherosclerosis and arthritis. Additionally, hormonal dysregulation from irregular sleep can lead to weight gain, as it alters ghrelin production, the hormone that stimulates hunger.
Prevention and practical care
Adopting simple habits can minimize the impacts of irregular sleep. Experts recommend small routine changes to align the circadian rhythm and improve overall health.
- Avoid caffeine at night: stimulants disrupt sleep onset.
- Relaxation routine: reading or meditation before bed prepares the body.
- Sleep monitoring: apps or wearable devices can identify irregular patterns.
- Medical consultation: essential for chronic insomnia or suspected apnea.
Neurologist Paula Vallegas emphasizes that prevention starts with awareness. “Many people don’t realize that irregular schedules affect health as much as sleeping too little,” she says.
Curiosities about the circadian rhythm
The circadian rhythm is a biological mechanism that regulates bodily functions over 24 hours. Its disruption can cause unexpected effects.
- Term origin: “circadian” comes from Latin “circa diem,” meaning “about a day.”
- Light influence: sunlight exposure is the main factor in synchronizing the biological clock.
- Animals and plants: the circadian rhythm also regulates behaviors in other species, like plant blooming.
- 2017 Nobel: the discovery of circadian rhythm molecular mechanisms earned a Nobel Prize.
These aspects highlight the complexity of the biological clock and its importance to health.