During adolescence sleep becomes shallower and shifts to later hours, reflecting extensive brain rewiring (Image: Sari Gustafsson/Rex Features)
New insights into our sleep requirements – from the amount we need to when, where and how we do it – have been supplied by recent research. The bottom line is that the quality of sleep varies from person to person and also changes throughout life
How much is enough?
A newborn baby may sleep as much as 18 hours a day, while a middle-aged executive may manage on as few as 5 hours. But how much is healthy and how much do we need? The short answer is that there is no answer: your needs depend on your age and gender, and it varies between individuals.
Young animals generally sleep more than adults and humans are no exception. The structure and intensity of sleep is different too. In young people there is a preponderance of REM sleep, and non-REM sleep is very deep, probably to aid brain maturation. Deep sleep and REM sleep both contribute to plasticity of neuronal networks, which could help with the acquisition of new skills. A recent study found babies sleep more during growth spurts ().
During adolescence sleep becomes shallower and shifts to later hours, reflecting extensive brain rewiring. The frontal lobe – responsible for executive functions such as planning and inhibiting inappropriate behaviour – shows a marked fall in synapse density as the result of neuronal pruning. Teenagers are not just being lazy when they don’t want to get out of bed. Their adolescent biology may also prefer an adjustment of school hours.
There…
![Astronomers have long known that understanding how star clusters come to be is key to unlocking other secrets of galactic evolution. Stars form in clusters, created when clouds of gas collapse under gravity. As more and more stars are born in a collapsing cloud, strong stellar winds, harsh ultraviolet radiation and the supernova explosions of massive stars eventually disperse the cloud, and their light can bear down on other star-forming regions in the galaxy. This process is called stellar feedback, and it means that most of the gas in a galaxy never gets used for star formation. Researching how star clusters develop can answer questions about star formation at a galactic scale. Now, the state of the art has been further developed with both Hubble and Webb working together to provide a broad-spectrum view of thousands of young star clusters. An international team of astronomers has pored over images of four nearby galaxies from the FEAST observing programme (#1783), trying to solve this mystery. Their results show that it is the most massive star clusters that clear away their gaseous shroud the fastest, and begin lighting their galaxy the earliest. The team identified nearly 9000 star clusters in the four galaxies in different evolutionary stages: young clusters just starting to emerge from their natal clouds of gas, clusters that had partially dispersed the gas (both from Webb images), and fully unobstructed clusters visible in optical light (found in Hubble images). With Webb???s ability to peer inside the gas clouds, they were able to then estimate the mass and age of each cluster from its light spectrum. This image shows a section of one of the spiral arms of Messier 51 (M51), one of the four galaxies studied in this work, as seen by Webb???s Near-Infrared Camera (NIRCam). The thick clumps of star-forming gas are shown here in red and orange, representing infrared light emitted by ionised gas, dust grains, and complex molecules such as polycyclic aromatic hydrocarbons (PAHs). Within these gas complexes, each tens or hundreds of light years across, Webb reveals the dense, extremely bright clusters of massive stars that have just recently formed. The countless stars strewn across the arm of the galaxy, many of which would be invisible to our eyes behind layers of dust, are also laid bare in infrared light. [Image description: A large, long portion of one of the spiral arms in galaxy M51. Red-orange, clumpy filaments of gas and dust that stretch in a chain from left to right comprise the arm. Shining cyan bubbles light up parts of the gas clouds from within, and gaps expose bright star clusters in these bubbles as glowing white dots. The whole image is dotted with small stars. A faint blue glow around the arm colours the otherwise dark background.]](https://images.newscientist.com/wp-content/uploads/2026/05/13114322/SEI_296271016.jpg)
