While my parents have lived reasonably long, my father until 90 and my mother until 86, they have both lost around 4-5 years of life because of illnesses that have been diagnosed much too late.
In both cases they belonged to risk groups for certain illnesses, but I was not aware of this. Now I wish there would have been some resource enumerating risks for older people and how to diagnose early the corresponding illnesses.
For example, my mother was 1. old, 2. woman, 3. taking for many years a medication against high blood pressure, 4. avoiding to eat much salt for fear of raising the blood pressure.
These 4 conditions create a high risk of hyponatremia and/or hypokalemia (too low content in the body of sodium and/or potassium, because they are eliminated too quickly from the body). Both affections are extremely dangerous.
To avoid any problems, it would have been enough if my mother would have made every few months a cheap blood analysis, to determine the sodium and potassium contents in the blood.
My mother actually made frequent enough analyses of the blood and all results had always been perfect. However, after she became seriously ill and eventually the cause was discovered, I have looked at the earlier blood analyses and while they had checked a myriad of other blood components, sodium and potassium had never been measured.
In the case of my father, he had smoked excessively a large part of his life until he has eventually succeeded to quit smoking. He was also overweight.
These 2 conditions together increase a lot the risk of renal cancer. Had we been aware of that, he should have attempted to check periodically for this.
As it was, the cancer was undetected for at least a couple of years, and it was detected only after it produced a bone tumor (the spread of renal cancerous cells to bones is a frequent occurrence), and even that was detected too late, because after a bone fracture, even if the symptoms had been as in a textbook example of bone cancer, some incompetent doctor diagnosed the symptoms as being caused by osteoporosis and arthritis and did not send him to the scintillation analysis that would have diagnosed the cancer immediately. I have also been too trustful and I did not seek a second opinion.
Due to the many cases of erroneous diagnoses, which happen much more frequently with older people, because the doctors tend to attribute any complaints to normal old age instead of sending them to multiple analyses to investigate for the real cause, it is good to seek second opinions whenever there is any doubt.
In conclusion, I believe that it is important to determine for each parent which are the main health risk factors and to test periodically for the most likely of the illnesses that might begin to affect them after a certain age.