Dennis,
I'm 4 years younger than you. In my 40s my BP was around 90/50, so low that I nearly failed my medical. Sadly the doctor died 6 weeks later. I'm told age does increase your BP & lack of exercise as well as poor diet. When I became a type 2 diabetic some 6 years ago, that became the end of my flying career.
I was put onto low GI diets & exercise to control my diabetes & it also controlled my BP. Generally my BP is 110-120 over 70-80. Last month I had a shocking head cold or flu & my BP was taken, 150/90! That shocked me because my BP was always low, often too low. When my cold/flu went this week, my BP was 120/80 & I expect will be lower next week.
So BP can change easily & if it goes up suddenly, there should be a reason which hopefully you can fix. Sadly my diabetes I can't fix & this week I started on 1 insulin shot at night, which means definitely no return to flying but then who wants a 78 year old commercial pilot! I wouldn't fly with me!
John, too many coffee & cakes!!