Interesting article in this week's The Economist, it's behind a paywall so I'll summarise.
Most of the body clears out cellular waste matter via the lymphatic system. But this process doesn't work for the brain, the brain flushes itself through using the pulsing of the arteries and cerebrospinal fluid. This process, called the "glymphatic system", clears out two types of brain protein, amyloid-beta and tau, which if they are allowed to build up can cause Alzheimer's.
Many factors can disrupt this process and increase the risk of Alzheimer's, but two of the most significant are disturbed sleep (the glymphatic system works best during deep sleep) and high blood pressure (especially amongst middle aged patients). Both of these are also risk factors for heart disease, so it's easy to see why there's a cross over between heart problems and dementia.
All this has been well documented before, but here's where the article gets interesting.
A large study in Denmark involving 70,000 patients found some (but not all) beta-blockers seemed to significantly promote better glymphatic circulation and therefore materially reduce the risk of Alzheimer's. The beta blockers that can do this are the lipid soluble types, I checked and this includes Bisoprolol, which many of us on this forum take.
So, good news if you're taking Bisoprolol, you're getting a valuable side benefit. But for all of us the study also underlines the critical importance of achieving regular, deep sleep. Stress, sleep apnea, shift work, over heated bedrooms, frequent long haul flights, and many other factors can all disrupt healthy sleep patterns. By tackling these it seems we can both improve our life style resistance to heart disease as well as reducing our Alzheimer's risks.