The relationship between a society's health and its wealth are very complex. We're all living longer, and it's widely believed this is due to improved standards of healthcare made possible by a wealthier society. Is that the end of the story? Of course not. We also eat and drink more, making us far more overweight than previous generations. If you look at the post WW2 populations, they were all very poor, with very little food about the place and loads of manual work to do. Pre-NHS and very poor, yet very healthy (apart from too many ciggies). Yet there are plenty of counter examples of populations where poverty is causing shortened lifespans.
The relationship between wealth and tax levels is also complex. A higher nett income after tax is no indicator of what we usually think of as 'wealth'. Availability of goods/housing/services, inflation, social infrastructure, crime, etc. all impact on how wealthy we feel, whether or not we have money in our pocket.
Lastly, we're all human beings, so we never feel 'wealthy'. We percieve the world in relative terms, so we only ever feel 'wealthier' or 'less wealthy' than other individuals, other countries, or ourselves last year/next year.
I think we've now reached consensus that this study is b*ll*cks.