from the article: "Legare said the findings contradict the common assumption that supernatural beliefs dissipate with age and knowledge."
It appears to me that the authors of the study (from the University of Austin, Texas) didn't simply verify that the older generation is more prone to supernatural thinking. One could argue that older generations weren't exposed to science, had less education, etc. But seems to me that the study, rather than taking a static 'snapshot' , observed a dynamic trend in the observed population. I would argue that greater ailments and the proximity of death that come with old age prompt a stronger propension to supernatural thinking.
Eden