Sleep is critical to peak health. Some of the adverse health effects attributed to too little sleep include obesity, diabetes, hypertension, heart disease, stroke, depression, impaired immune function, increased pain, impaired performance, and greater risk of accidents.

Conventional wisdom dictates that everyone needs approximately eight hours of sleep per day to properly function. This is in line with past recommendations by the American Academy of Sleep Medicine (AASM) and Sleep Research Society (SRS) that every adult should sleep 7 or more hours per night for optimal health.

However, in a recent study published in Proceedings of the National Academy of Sciences (PNAS), researchers found that everyone does not need the same amount of sleep to be healthy. In fact, the optimal amount of sleep for you may depend on your culture.

Scientists from the University of British Columbia (UBC) and the University of Victoria (UVic) analyzed data on sleep and health outcomes for nearly 5,000 people in 20 countries across North America, Europe, Asia, Africa, and South America. First, they confirmed previous findings that average

sleep time varies widely from country to country. For example, the average in Japan was six hours and 18 minutes, while in Canada it was seven hours and 27 minutes, and in France it was seven hours and 52 minutes. A chart from the study showing average sleep duration by country is shown in Figure 1 below.

“Despite the common advice to get eight hours of sleep, our findings suggest that sleep recommendations need to be adjusted based on cultural norms,” said Dr. Steven Heine, Professor of Social and Cultural Psychology at UBC and a co-author of the study. “There is no one-size-fits-all amount of sleep that works for everyone.”

Second, they assessed whether individuals in countries with shorter average sleep times had poorer health outcomes than individuals in countries with longer average sleep times. They found that people in countries with less sleep were just as healthy as those in longer-sleeping nations.

“People who slept closer to their own culture’s norms for sleep duration tended to have better overall health,” said Dr. Christine Ou, Assistant Professor in the School of Nursing at UVic and the lead author of the study. “This suggests that the ideal amount of sleep is the amount that matches what is considered appropriate sleep in one’s cultural context.”

Their findings highlight how important it is to keep cultural context in mind when making sleep recommendations. Public health guidelines regarding sleep can promote better health outcomes if they are designed to consider the cultural norms of different populations.