Caffeine has an average half-life of 5-7 hours. Ageing can affect the speed of caffeine clearance, the older we are the longer it takes our brain and body to remove it. (This means that the older we are, the more sensitive we become to the Sleep-disturbing effects of caffeine).
Let’s say that you have a cup of coffee after your evening dinner, around 7:30 p.m. This means that by 1:30 a.m., 50 per cent of that caffeine may still be active and circulating throughout your brain tissue. In other words, by 1:30 a.m., you’re only halfway to completing the job of cleansing your brain of the caffeine you drank after dinner.