On your parenthetical, here's a hypothesis. It's kinda hard to be old in rural areas(no way to get around, limited care available, etc), which tend to be inland

On your parenthetical, here's a hypothesis. It's kinda hard to be old in rural areas(no way to get around, limited care available, etc), which tend to be inland, whereas cities tend to be coastal or situated on a river. So I could definitely see it as plausible that the older people get, the more people move into cities, which coincidentally involves moving closer to water.