Will a regular exercise routine and a healthy diet keep your brain young? It depends on your genes. People who have certain forms of genes that play a key role in brain ageing seem to respond better to healthy lifestyle interventions. These make it "more likely that exercise or adhering to a Mediterranean diet will have a greater impact on your cognitive ageing," says Sandrine Thuret at King's College London. Cognitive ageing is thought to rely on neural stem cells in the brain's hippocampus which continue to produce new neurons throughout life, and are thought to play an important role in forming new memories.

Retiring well & aging independently requires more than health and wealth, it requires a supportive community. On an extraordinarily hot Independence Day weekend, I visited my elderly mother-in-law in her quiet suburban community on the edge of Boston, Massachusetts. She lives alone and mostly independently. Part of my wife's and my weekend ritual is visiting and running errands with her. As we walked down her driveway, we saw a black car drive slowly down the quiet, empty street. A man stuck his head out the window and asked whether I had seen an older Asian man dressed in dark clothing walking through the neighborhood.