Study: Smoking not associated with dementia

March 26 (UPI) -- Cigarettes may lead to many bad health outcomes, but a new study has just crossed one of them off the list.

Smoking is not linked to developing an increased risk of developing dementia, as many scientists once thought, according to new research published Tuesday in the Journal of Alzheimer's Disease.

These new findings contrast sharply with years of research that pointed to smoking as a factor for the disease.

"The underlying data (in those studies) was solid, but the analysis didn't take into account the idea of competing for risk of mortality, which we felt was an important factor to consider in this case since smoking is so strongly associated with earlier death," said Erin Abner, a researcher at the University of Kentucky and study author, in a news release.

Competing risk can interfere with a study's conclusions by assuming that a certain risk factor is the cause of a condition when another one is present and possibly the actual cause.

For example, if researchers were exploring the link between poor sleep and heart disease. A study participant with bad sleeping habits may die of a heart attack brought on by obesity. That death, however, shouldn't factor into the study's results.

To test for competing risk, the researchers used a Competing Risk Analysis to test the results of 531 initially cognitively-normal people participating in another study that examined the effect of aging on cognition.

With two risk factors in place, the researchers were unable to find any clear connection between smoking and dementia. Although they also acknowledge that the Competing Risk Analysis isn't the standard method for dementia testing when another risk is clear and present.

About 14 percent of adults in the U.S. smokes cigarettes, while an estimated five million people have dementia, according to the Centers for Disease Control and Prevention.

"While our study results could influence smoking cessation policy and practice, we feel that the most important consequence of our work is to demonstrate how this method could change the way we approach dementia research and to advocate for its adoption in the appropriate areas of study."