Two different definitions of old - the author seems to be saying as people get older while still in the working realm [so maybe, 20-65 or so] while the study talks about the elderly/seniors. So not necessarily conflicting [and it might make sense that a person gets more and more dissatisfied as they get older and opportunities slip away until they finally let go of those regrets and become satisfied with their lot]. More on age/happiness:

http://www.slate.com/toolbar.aspx?action=print&id=230055...