I’m not looking at any specific disease at the moment: I look at genetic effects on normal variation in thinking ability in healthy older people, and how that changes over time.
The distinction between a “genetic” disease and “ageing” disease is a slippery one. There are some diseases, like Alzheimer’s, which mostly affect old people. But it wouldn’t be entirely accurate to say it’s JUST caused by old age: the types of genes you carry will change the chances you have of developing the disease. There are even some kinds of genes that make you develope Alzheimer’s early in life.
As with most diseases, the risk of getting dementias like Alzheimer’s is down to a mix of genes and environment. We can try and control our environment as best we can, and if we’re able to work out what genes go wrong, we can try and do something to fix them. Even the work I’m doing on normal variation can be useful there: genes that affect normal thinking ability are likely to be the same ones that go wrong in diseases like dementia.