"The mean age of death for tattooed persons was 39 years, compared with 53 years for non-tattooed persons (P = .0001). There was a significant contribution of negative messages in tattoos associated with non-natural death (P = .0088) but not with natural death."
TFA has a more direct, physical, concern - it starts from a well-known, that tattoo ink ends up in lymph nodes, and it does a statistical analysis showing there's a significant statistical result in lymphoma occurence.
I think people with negative tattoos dying younger reduces the # of people with tattoos who get lymphoma, as they have less ink-in-lymph-nodes years.
I doubt they intended to communicate something that general, and if they did, I doubt they meant to pick one that would reinforce the conclusion.