New Delhi: Sleep patterns vary significantly around the world, influenced not only by individual habits but also by geography, the season, and the day of the week, according to a new international study led by Flinders University. The research analysed over 73 million nights of sleep from more than 116,000 adults globally, using an FDA-cleared under-mattress device to track sleep duration and timing over 3.5 years.
Lead author Dr Hannah Scott from the Flinders Health and Medical Research Institute (FHMRI) Sleep Health explained that sleep patterns are deeply connected to the surrounding environment. She noted that their findings "underscore the seasonal nature of human sleep, and that it is influenced by demographics and geography."
According to Dr Scott, whether it is daylight hours, temperature, or our weekly routine, these external factors have a surprisingly strong influence on the quality and quantity of our sleep and wellbeing. She added that "importantly, it is normal to experience variations in our sleep across the seasons, and this seems partly driven by where we live."
The study found that people in the Northern Hemisphere sleep 15 to 20 minutes more during winter, while those in the Southern Hemisphere, including Australians, tend to sleep less during the summer months.
Dr Scott pointed out that "interestingly, we found that the farther you live from the equator, the greater the seasonal variation in sleep." She explained that Australians living further from the equator, such as in southern regions like Melbourne or Hobart, "may feel the impact of these seasonal shifts more acutely than those in the tropics."
Sleep schedules also differ markedly between weekdays and weekends. Co-lead author Dr Bastien Lechat reported that "whilst people stay up later at the weekends, going to bed on average 30 to 40 minutes later than weekdays, they are also sleeping in longer – up to 80 minutes – on Saturdays and Sundays."
He emphasized that "these changes to sleep schedules might seem small, but they can have a dramatic impact on our body clocks." The largest weekday–weekend differences in sleep duration were observed among adults aged 40 to 60 years, which the researchers believe relates to the challenges of balancing full-time work and family responsibilities. This aligns with concerns that irregular sleep can be linked to adverse health effects.
In addition, the study identified a subtle but steady decrease in overall sleep duration over the period studied, with people sleeping approximately 2.5 minutes less per night between 2020 and 2023. The researchers speculate this decline may be tied to lingering effects of the COVID-19 pandemic.
Senior author Professor Danny Eckert emphasized that irregular sleep should not be dismissed as simply feeling tired, as it "can be a health risk, and understanding how our routines and environments affect sleep is a helpful step towards improving it."
He added that "still, the research marks a major step forward in understanding how human sleep is shaped by our surroundings – and it’s a reminder for us to be mindful of the clock, the calendar, and even the seasons when it comes to getting a good night’s rest."
The researchers also acknowledged that although this study is one of the largest of its kind, its sample skewed toward tech-savvy individuals who already use sleep-monitoring devices, and did not account for other factors such as pets, children, or sleeping partners. Nevertheless, they consider it an important step in understanding how our surroundings shape human sleep.