Do you get enough daylight? Probably not, like most of us these days. …. but you should!

“Light not only affects your body clock and your sleep, it can act directly on your mood”

Katharina Wulff, a daylight researcher at the university of Umea in Sweden

Shocking?  We know that being exposed to daylight is important. Leaving in Ireland where winter light is rare, I have suffered for years from Seasonal Affective Disorder  (see my article on SAD) so I know first hand how the lack of daylight can affect your mood. but do I really? I mean I know it is the case, but how exactly does it affect my mood?

Days in Ireland in the winter are short. On a cloudy day, you nearly have no light at all. But today, no matter where you are in the western world, you are most likely not getting enough light. 

Today, the average westerner spends 90% of their life indoor. 

Long gone are the days where we all worked outdoor, or went out for lunch time. We spend more time indoor than we used to.

Today offices work means that we are more indoor. Also, entertainment such as TV, games, tend to keep us more inside.

These new patterns are increasingly linked to disrupted sleep and circadian rhythms – which has consequences on our physical and mental health. It also contributes to vitamin D deficiency, which can be undermining our immune system and cardio vascular  system as well.  

The reality is that this lack of exposure to day light affect our sleep, it affects our moods. And research confirm it. 

So how much light do you need? 

It is still unclear how much daylight is necessary to optimize health, and it may well differ depending on what you are trying to achieve. So there is no exact number, but what we can do is compare to our ancestors (or communities living in a more primitive way) to understand how much less light we get today?

Light exposure is measured in LUX.  

LUX is the SI unit of illuminance, equal to one lumen per square metre.

The Amish community, which probably spends more time outdoor, maintaining a more primitive lifestyle,  are exposed to an average daylight illuminance of 4000 LUX in the summer, compared to 587LUX for an avg person in the UK. IN the winter, this goes down to 210 LUX. 

We clearly are not getting enough light compare to our older generations, that’s for sure

How much light to you get indoor?

Outdoor daylight is around 10,000 LUX (on a sunny day). The same light through a window is reduced to 1000LUX. If you stand a few metres from that window, you probably get a fraction of that, and the artificial lighting from your office will provide, if you are lucky, a maximum of 400LUX.

Outdoor daylight is around 10,000 LUX. The same light through a window is reduced to 1000 LUX

We clearly need to spend more time outside since indoor light as it is doesn’t make the cut. Getting back to simple habits of getting out of the office at lunch time for instance can go a long way rather than staying indoor, even if it feels bright. 

Lights affect sleep

A research led by the General Services Administration in the US, found that staff who got more Bright light during the day, felt asleep faster and slept longer than those who don’t  (took them 18min to fall asleep vs 45min), and slept 20min longer. 

This is of course to be put in contrast with the negative effect of Blue Light in the evening (see my other article on Blue Light).

Lights affect our mood

But as mentioned above, today we finally understand while light can affect your mood, in a much more direct way than we ever thought before. Research in mice provide insights into what happens.

The same research led by the General Services Administration in the US, found that greater daylight exposure was associated with lower scores on self-rated scale of depression.

Basically, we have light sensitive cells at the back of our eyes (ipRGCs) which fire responses to any light (especially blue part of the spectrum) and send signals to areas of the brain that control alertness. The same ipRGC that feed into the brain master clock also connect to the Thalamus, a brain area related to mood. “This is a hugely, important finding” says Katharina Wulff, a daylight researcher at the university of Umea in Sweden. ‘It shows that light not only the clock, it can directly act on mood” 

‘This is hugely important finding. It shows that light not only affect the clock, it can directly act on mood” 

Katharina Wulff, a daylight researcher at the university of Umea in Sweden

so whether direct or indirect, lack of daylight impact your sleep, your mood, which are some of the main symptoms of SAD, so my advice is to start getting some daytime outdoor break.

Also, there are apps which measure the LUX. I downloaded one to confirm the numbers above, and this is really interesting to measure the actual light in various places, gives you a better sense of how “little” light you are getting.

Light can reduce recovery time in hospital environment

Finally, one study also found that hospital patients recover faster when they have more access to daylight.

In one study, the average length of stay for people recovering from heart surgery was reduced by 7.3h for every 100LUX increase in daytime illuminance

Linda geddes, new scientist consultant

It is still unclear why, but it is significant enough when a 2017 study found that the average daytime illuminance in a UK intensive care unit was 159LUX.

May be they should start looking into it …