My personal theory is that the brain has a "refresh" rate similar to a CPU clock. Metabolic processes, especially the time it takes for neurons to achieve the chemical balance to fire another signal likely degrades as we age.

As this Brain Refresh starts to slow, so does our perception of time. I don't think it is just linked to memory formation and recall as the article suggests. It is more likely a structural thing.

This means that every process is affected, though it isn't as if your heart rate slows just because you are aging. I'm talking simply about the reuptake delay that creeps into the neurons themselves.

You could have an acceptable amount of decay in this refresh without interfering with the autonomic systems that the body runs on its own, like breathing and pumping blood.

So we age, our brains strobing and sensing just a fraction slower than we normally would. And as it does so, we experience time speeding up as our cells slowly give in to entropy.