You can spend a whole fortune on creams, but if you sleep badly, your skin knows it before the mirror does. Pharmacist Marta Masi explains something the beauty industry doesn't advertise loudly: bad sleep, insomnia and apnea are linked to faster skin ageing - and at the level of the cells themselves.

The key lies in the telomeres - the protective ends of chromosomes that work like caps on DNA. They naturally shorten with every cell division, but the process can be sped up by external factors, sleep quality among them. "Bad sleep, insomnia and apnea are linked to shorter telomeres", Masi says. When telomeres shorten too much, cells lose the ability to divide properly and enter a state of dormancy - more inflammation, weaker tissue renewal, more wrinkles, sagging skin and blemishes.

Then there's the stress hormone. Chronic sleep deprivation raises cortisol, increases inflammation and oxidative stress - all conditions that accelerate cellular ageing. Conversely, quality sleep is the time when the skin actually repairs itself: cells renew and collagen is synthesised. In other words, the priciest night care is free and it's called - sleep.

Masi's recommendations aren't revolutionary, but they work: a regular sleep schedule, morning exposure to light, no screens before bed, a light dinner, less alcohol and caffeine in the afternoon and a calming pre-sleep routine. None of it comes in a bottle - and maybe that's exactly why we hear it less often from the people who make their living selling creams.