This is The Guardian.

Two weeks into January and those New Year's resolutions are already starting to feel like a bit of a drag.

You've hit the wall on your exercise regime. Treats start to look very tempting,

and work is full of stress again.

But what if I told you there's one health hack

that can help with all those things and more? Plus, it's relaxing, enjoyable and free.

Sleep. Getting a good night's rest is great for our physical and mental health, and yet more

than ever, it feels difficult to achieve.

So to help kick off 2026 in a more restful way,

we're putting your sleep questions to an expert.

From The Guardian, I'm Ian Sampal, and this is Science Weekly.

Dr. Ali Hare, you're a consultant physician in respiratory and sleep medicine at Guy

in St Thomas's Hospital and President of the British Sleep Society.

I'm going to kick off with a listener question which came in from James. Hey, I'm James and I would like to know what the main factors are

in controlling your circadian rhythm and more specifically, what is it that controls your wake-up time

and whether or not that can actually be influenced.

I've tried everything from smart lights that turn on with the sunrise to alarms that

monitor my heart rate via my smart watch so that they only turn it on when I'm out of a sleep cycle

and nothing seems to budge it. My wake-up time always seems to be way later in the

morning, you know, not exactly great for a night to five. So I'd just love to know if there's anything

I could do about that. Thanks. So, Ali, what do we know about how our individual sleep patterns

are set up and are they malleable? So in answer to the first part of the

...