A new study from the University of South Australia (Pham et. al.) has looked at coffee consumption and possible associations with brain matter volume, stroke risk, and dementia risk.
(Photo credit: Janko Ferlič, Viskafors, Sweden)
The study was a prospective analysis using 398,646 patient data from the UK Biobank, with a subset of over 17,000 patient data with associated MRI scans.
They found that the association between coffee consumption and dementia was non-linear (P = 0.0001), with evidence for higher odds for non-coffee and decaffeinated coffee drinkers and those drinking >6 cups/day, compared to light coffee drinkers. They also found an association between >6 cups/day and decreased brain volume, but no conclusive link to increased risk of stroke.
Essentially, according to the study conclusions, drinking 1 - 2 cups/day of coffee is associated with decreased risk of dementia compared to non-coffee or decaf coffee drinkers and those who drink >6 cups/day has the highest risk for developing dementia (hence why the study mentioned the relationship is non-linear).
The study has limitations in that it does not look at potential causes but only correlations, and as we all know, correlation does not equal causation. However, if one were to take an educated guess as to why the highest coffee consumption is linked to increased risk of dementia, it is that high caffeine intake, especially during later parts of the day, can adversely affect sleep. Decreased sleep or unrestful sleep is also linked to a heightened risk of dementia.
Many sleep experts caution coffee lovers to not drink coffee after 2 PM (for those with a regular 9AM - 5PM work schedule), since coffee has a half-life of approximately 3 to 5 hours (it takes this long for your body to process and get rid of half the caffeine in your system after intake).
In conclusion, as with all things, enjoy coffee in moderation (1-2 cups per day some time in the AM should be considered the ideal).