Blood pressure during sleep can get much higher than awake due to snoring apnoea. This is key marker for cardiovascular risk but very hard to measure without help or Aktiia type device. As one is lying pressure should be around 7 less due to relative position or heart, eg 113/68 vs sitting 120/75. Only a few automatic reading would be needed each night, say every hour. Over several nights abnormal levels during night should get captured. The valuesdont need to be very accurate, just be able to show if bp became elevated while sleeping, ie the trend. These abnormal levels can kill as indicate heart starved of O2. Aktiia continuous bp monitor does this and costs £200 - please check yoyrybe reviews for concept. I think it would be extremely easy for Samsung to implement in a software update and would make the smartwatch a very valuable medical tool. At present the day time readings lull users into thinking their bp is ok when it may not be and so are actually misleading. This is well known by medics but not by public. Due to difficulties monitoring health authorities dont highlight this risk but doctors on youtube cite deaths from it. It would be trivial for Samsung ti fix this and save lives.
