So much of our health is tied to banking good quality sleep every night, and a new four-week experiment has revealed a simple way anyone can improve the quality of their slumber: keeping the bedroom well-ventilated.

A team led by researchers from the Technical University of Denmark analyzed the sleep of 29 volunteers, using existing ventilators in their own bedrooms to vary the rate at which air was cycled overnight.

Low, moderate, and high ventilation rates were compared to a baseline week where no changes were made to the current habits of the participants. As ventilation rates went up, sleep quality also went up, and the number of overnight awakenings went down.

Bedroom ventilation
(Fan et al., Science of The Total Environment, 2023)

"Objectively measured sleep quality was improved when the ventilation rate was increased by increasing the fan speed," write the researchers in their published paper.

Sleep quality was assessed with wrist-worn trackers, but the researchers took many more measurements as well. For each ventilation setting, they recorded carbon dioxide (CO2) concentration, humidity, particulate matter (PM) levels, and temperature.

As you might expect, ventilation rates had a significant impact on CO2 and PM levels, with less ventilation meaning higher concentrations in both cases. The team also noticed that higher ventilation rates reduced the humidity in the bedrooms.

Although earlier research has linked poor ventilation and poor cognitive performance, this study didn't show any difference in cognitive capabilities in the morning as the ventilation rates in the rooms were adjusted overnight – possibly because the CO2 levels stayed below a certain threshold, the researchers suggest.

The researchers are keen to carry out further experiments in which the relationship between factors like CO2 concentrations and humidity are more closely examined, in terms of how they affect sleep quality. What these results suggest, though, is that a well-ventilated room means a better night's sleep – whatever the underlying reasons.

Previous research has also linked better ventilation to better sleep, but in this particular study, the team wanted to monitor people in their own beds, and change the ventilation conditions – via remote control – without the participants being aware.

That real-world setting gives the study a little more weight, though it has some limitations of its own – including the relatively small number of participants. The researchers are hoping to run similar experiments on larger groups of people in the future, but in the meantime, if you are waking at night, you might want to run your own experiment and increase the ventilation in your bedroom.

"Further studies with larger populations and better control of bedroom conditions, particularly ventilation, are required," write the researchers.

The research has been published in Science of the Total Environment.