I'm way way older than 40, but the side of the family I most take after has a genetic history of living into our 100s with no significant illnesses. My great grandfather lived until he was 103 and was perfectly healthy in all ways until 2 weeks before he died when very quickly his body shut down and he passed away. No illnesses, just pure old age. His daughter, my grandmother, will be celebrating her 100th birthday soon. She still drives, walks without assistance, lives alone in her own home, etc. I'm not exactly a spring chicken, but I have zero health issues. I don't even ever have headaches. So, most likely I'll avoid the terrible deaths. Here's hoping.