Longevity Vs. Retirement Age

Here's a report about the relationship between longevity and retirement age that claims that early retirement is the key to long life. But here's a BBC article that says the opposite: "Early retirers don't live longer". The thing is that retirement age and longevity aren't independent variables! Among the many dependencies, smarter people tend to live longer and could also save up money to retire earlier; sick people might retire early for health reasons and also die younger. Each person will have their own reasons for retiring or not, and their own risk factors that affect their longevity.