First, the time period of the study is too short for meaningful results. This kind of study would need to go on for decades to be credible.
Second, there's no way the researchers could have accurately collected the data needed for this study from a group as large as 500,000. Just think of the logistics required. There's no one on planet Earth who could accurately collect the data needed.
Finally, the 500,000 would need to have been selected randomly and all of the random selections would have had to agree to participate in the study. There's no way the study population could have been a true random selection.
In short, any reported results from this charade are pure BS.
Actually, most medical research studies are similarly flawed, which is why so much of what we think we know from such bogus studies turns out to be pure crap.
Is any crap really pure?