Although our results can explain a great deal of general factors related to longevity, there remain inexplicable phenomena. For example, a minority of cities located in the Tibetan plateau also have a mid-range longevity ratio (the 85+/65+ ratio is between 0.06 and 0.07). Interestingly, the altitude there is >3000 m and many find the climate intolerable. Examples such as these warrant further investigation and discussion.