Just curious as to whether you can clarify something that I still wonder and have never quite understood. It seems to be often said that we can't change our cortisol levels and time of HGH production by sleeping in a different pattern… so my question is, is this governed by daylight? On going on holiday or emigrating I assume these levels adjust to the new daylight hours?

And from that another question is similarly if work habits mean you sleep in complete darkness until say 10am or later, and only then start getting your daylight doesn't this have the same effect as moving to a different geographical timezone i.e. wouldn't your body then begin to consider it's first sign of daylight to be equal to 6am and begin to adjust these levels implying that we do indeed manipulate them by changing when we get up and go to bed? You can probably see why I'm confused by the apparent contradiction… this never seems to be quite clarified in any of the articles I read on the topic so hoping you can help thanks.

Yeah, I think that I can help with that. If you travel to a new country or emigrate, you are likely to keep a similar daylight schedule- and yes it IS governed by daylight/night. So, if you go to a new country, the daylight/night think will readjust. But if you simply take a night shift, then you are still sleeping during the daytime and working at night. No matter how hard you try, you’re just simply not going to fool your body that you are sleeping at night. It knows that you are not.

And most night shift workers aren’t consistent 7 days a week with their schedule. On their days off, they often change schedules back to daytime, then switch back after their weekend. So, your body is always changing around and that’s not so good for cortisol and HGH levels- which is likely one of the reasons why night shift workers have higher cancer rates.

Kerri