The impact of unusually high temperatures in the summer of 2022 on infants’ sleep

In a recent study published in the Scientific Reports Journal, researchers investigated how the intense summer heat of 2022 affected the sleep patterns of infants and toddlers.

Study: The impact of extreme summer temperatures in the United Kingdom on infant sleep: Implications for learning and development. Image Credit: ArseniiPalivoda/Shutterstock.com

Background

According to the U.S. Global Change Research Program, extreme heat is becoming more frequent and intense worldwide. The significance of sleep for healthy development and growth is often disregarded in scientific studies exploring the effects of climate change on infant health.

The present study addressed this gap in knowledge by investigating the effect of abnormally high temperatures during the summer of 2022 on the sleep patterns of infants by objectively assessing the sleep patterns of infants in their homes using Nanit camera monitors.

About the study

The study involved the participation of 413 infants' parents. Nanit baby monitor users were invited via email to join a study exploring the correlation between climate change and sleep.

The team evaluated infant sleep using Nanit camera monitors furnished over the infant's crib at home.

Nanit app allows users to define the crib area, enabling the computer vision algorithm to interpret motion trends as sleep or wakefulness. The algorithm also identifies when a parent enters the designated area.

The study examined three metrics: total sleep time (TST), sleep efficiency (SE), and minutes to sleep onset (MSO). The number of night wakings (NW) and parental visits to the crib (visits) were also measured.

The study primarily determined if infants' sleep was affected during the three heat waves in the Summer of 2022. The researchers explored a changepoint assessment on all sleep estimates. The within-subject average of each sleep estimate was utilized over 84 nights without a heatwave. The deviation from each sleep estimate on each night was calculated compared to the within-subject average.

Results

Deviations in infants' total sleep time surpassed the threshold on 17 July, 19 July, 24 July, and 14 August. Infants' overall sleep duration had significantly altered during those particular nights. Infants slept less by an average of 0.06 hours during nights affected by heatwaves up to 17 July. Infants experienced a reduction of 0.34 hours in their sleep duration during the second heatwave, between 18 and 19 July, compared to the average calculated for non-heatwave nights.

Between 20 and 24 July, infants slept slightly less than the average non-heatwave nights by 0.02 hours. During the third heatwave, which ended on 14 August, infants slept somewhat more than usual, with an increase of 0.02 hours compared to non-heatwave nights. Infants slept an additional 0.14 hours following the third heatwave compared to the average duration of non-heatwave nights.

The sleep onset patterns of infants were altered on 7 July and 15 August. Infants fell asleep 0.84 minutes earlier on average during heatwave nights up till 7 July compared to non-heatwave nights.

During the period between 8 July to 15 August, infants took 1.37 minutes longer to fall asleep compared to the average of non-heatwave nights. Infants fell asleep 0.47 minutes earlier than usual on nights following 16 August, unaffected by heat waves.

Infants' sleep efficiency was significantly altered on five specific dates 15 June, 17 June, 6 July, 19 July, and 21 August. Infants' sleep quality was slightly lower, averaging 0.20% less than non-heatwave nights, until 15 June.

Infants' sleep quality also decreased by approximately 2% during the first heatwave on 16 and 17 June. Infants' sleep quality experienced a 0.20% decrease between 18 June and 6 July. During the second heatwave, which ended on 19 July, infants experienced a reduced sleep quality of 0.90%.

Furthermore, infants' sleep quality showed a slight increase of 0.10% between 20 July and 21 August. Also, the sleep quality among infants was slightly better than non-heatwave nights, with a 1.3% increase observed after 22 August.

The number of night wakings in infants showed significant changes on 26 June, 9 July, 17 July, 19 July, and 14 August. Infants woke up an average of 0.18 more times than non-heatwave nights until 26 June. Infants experienced a 0.02 increase in wake-ups between 27 June to 9 July.

Between 10 and 17 July, infants experienced 0.23 more awakenings than the average number on non-heatwave nights. Furthermore, infants woke up 0.69 times more during the second heatwave between 18 and 19 July.

During the recent heatwave between 20 July and 14 August, infants woke up almost 0.04 times less than they typically do on non-heatwave nights. Also, infants woke up 0.32 fewer times after 15 August.

The frequency of parental visits showed significant changes on 9 July, 17 July, 19 July, and 7 August. During heatwave nights until 9 July, parents visited the infant on average 0.10 times more often than on regular nights. Parents increased their interventional visits by 0.26 times from 10 July to 17 July.

Parents intervened 0.67 times more often during the second heatwave between 18 and 19 July. During the period between 20 July to 7 August, there was a 0.03 increase in parental intervention. Parents' interventions decreased by 0.28 times after 8 August.

Conclusion

Sleep disruptions during three heat waves were linked to the temperature's absolute value rather than the relative value that defines a heat wave.

This association was observed across various sleep metrics. Studies have also shown that climate change-induced temperature elevations negatively affect sleep among adult persons.

The team noted that failure to stabilize temperature elevations, like those experienced during a heat wave, could result in up to two weeks of annual sleep loss.

Written by

Bhavana Kunkalikar

Bhavana Kunkalikar is a medical writer based in Goa, India. Her academic background is in Pharmaceutical sciences and she holds a Bachelor's degree in Pharmacy. Her educational background allowed her to foster an interest in anatomical and physiological sciences. Her college project work based on ‘The manifestations and causes of sickle cell anemia’ formed the stepping stone to a life-long fascination with human pathophysiology.