I know this data. It's as good as it's going to get, and I agree it's scientific. However, the number of variables are just too large for the data to be accurate.It's very scientific:
Estimating Smoking–Attributable Mortality in the United States (nih.gov)
By the way, I quit cold turkey exactly 29 years and 12 days ago.
It took a 12-step program for me to quit smoking (5,428 days and counting) and 122 extra pounds.