Almost everyone knows that it’s probably not a good idea to drink coffee later in the day, but the question really is when? With caffeine now found in so many more foods and drinks, it’s quite easy to catch yourself consuming caffeine – in coffee, energy drinks, chocolate bars, even medicine – much later than you’d planned.

It’s undisputed that caffeine has sleep-disrupting effects. A recent study also concluded that heavy caffeine consumption is linked to higher mortality rates in men and women. So, it’s worth considering about how much caffeine you really are consuming daily.

How does caffeine affect sleep?

But, until fairly recently, the effect of caffeine on sleep had not been fully investigated. Now, we have a better idea. The Henry Ford Hospital’s Sleep Disorders & Research Center and Wayne State College of Medicine, both in Michegan, analysed the sleep-disruptive effects of caffeine consumption at different lengths of time before bedtime.

They discovered that caffeine consumed even six hours before bedtime resulted in significantly diminished sleep quality and sleep quantity.

What's the latest time to drink coffee without it affecting your sleep?

This is an important discovery. So, let’s say, you’re average bedtime is 10pm or 11pm on a “school night”. If it’s 10pm, they’re talking about an effect if consume a coffee at 3.30pm (don’t forget that it takes time for the caffeine to take effect once you’ve drunk it).

So, you really should stop drinking coffee by 3pm latest.

So, how did this study exactly work?

Well, a bit caveat is that it only had a sample size of 12 men and women. Very small indeed. All the subjects were healthy and were normal sleepers and moderate consumers of caffeine.

During the study period volunteers kept up their daily and night time routines and were monitored through sleep diaries and sleep monitors. Participants were then given doses of caffeine in pill form as well as placebo pills, on a schedule that enabled researchers to measure the sleep-disruptive effects of caffeine taken at three different points: and six hours before bed, three hours before bedtime and finally at bedtime.

Their results were as follows:

  • There was perceived disruptions to sleep for caffeine consumed at bedtime and three hours before bed, but were not reported for caffeine taken six hours before bed. However, computer sleep monitors measuring total sleep time, and sleep efficiency showed that caffeine consumed six hours before bedtime had significant detrimental effects.
  • Caffeine consumed at all three points diminished sleep quality. Caffeine taken three and six hours before bedtime, as well as caffeine consumed at bedtime, significantly increased the amount of time spent awake during the night.
  • Caffeine consumed zero, three, and six hours before bedtime significantly reduced total sleep time. Indeed caffeine consumed six hours before bed reduced total nightly sleep amounts by more than one hour.

So, despite the small sample study, this investigation appears to have some clear lessons for us about how much coffee or caffeine we consume in the afternoon and evening.

So, what time should we stop drinking coffee?

Here are our tips:

  • Stick to a 2 o’clock cut off for consuming caffeine. If you do have a midday cup of coffee, make sure to drink it before 2 p.m.


  • Avoid large size coffees. In short no grande, jumbo or super size drinks. Be aware of how much caffeine is in each cup of coffee. They vary dramatically depending on the type and size of brew.


  • Reduce caffeine as the day progresses. Start your day with your most highly caffeinated beverage and taper down on caffeine as the morning goes on. Perhaps, switch to herbal tea or decaffeinated coffee as the morning continues so as to be caffeine-free by mid-afternoon.


In short, it’s not about cutting out caffeine, but just being aware of your consumption and planning your day with a little more thought about what you put in your body after 2pm!

August 13, 2016 — Guy Wilmot

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