Your morning coffee cuts dementia risk by 18%. Decaf does nothing. Harvard tracked 131,821 people for 43 years to figure out why. Caffeine is an adenosine antagonist. Adenosine is the molecule that builds up in your brain through the day and makes you sleepy. It also dampens the neurotransmitters involved in memory formation. Caffeine blocks the receptor before adenosine can lock in. Memory circuits run less suppressed than they would otherwise. That's why decaf failed. Decaf has the same…