Daijiworld Media Network - New Delhi
New Delhi, Oct 8: Rising nighttime temperatures caused by climate change may have significant effects on mental and physical health, with a new study finding that exposure to heat at night can increase anxiety, disrupt sleep and trigger changes in biological stress markers.
Researchers conducted a randomized controlled crossover trial involving 41 healthy college students aged 18 to 25 to examine the psychological and biological effects of daytime and nighttime heat exposure.
Participants experienced daytime heat at 32°C for eight hours, from 9 am to 5 pm, and nighttime heat at 30°C from 10 pm to 6 am. These conditions were compared with a thermoneutral environment maintained at 26°C.
The researchers assessed participants' anxiety levels and biomarkers linked to inflammation, oxidative stress, cortisol and brain-derived neurotrophic factor (BDNF) before and after heat exposure.
The findings showed that heat exposure increased state anxiety and was associated with changes in several biological indicators. Daytime and nighttime heat exposure were linked to increases of 24.71% and 27.80%, respectively, in state anxiety scores.
Nighttime heat exposure was associated with a wider range of biological changes than daytime heat. It increased levels of the inflammatory biomarker interleukin-1β and the oxidative stress marker malondialdehyde (MDA), while also raising cortisol levels and reducing BDNF levels.
Participants exposed to nighttime heat also reported poorer sleep quality and shorter sleep duration.
The study found that MDA and cortisol partly mediated the association between nighttime heat exposure and anxiety, accounting for 14.42% and 6.88% of the association, respectively. No significant mediating effect was observed for the biomarkers examined following daytime heat exposure.
Researchers suggested that the stronger effects observed at night could be linked to disruption of the body's recovery processes during sleep. Heat during sleeping hours may interfere with sleep quality and circadian rhythms, potentially affecting psychological and neurological regulation.
The increase in cortisol during nighttime heat exposure also suggested a possible disruption of normal neuroendocrine activity. Cortisol typically remains relatively low at night and plays an important role in the body's response to stress.
The researchers said the findings provide experimental evidence that short-term heat exposure can affect anxiety and point to possible biological pathways involving oxidative stress and neuroendocrine responses.
However, the study was limited to young, healthy college students and examined only short-term heat exposure. Further research is needed to understand the effects of prolonged or repeated nighttime heat exposure on mental and physical health.