For the study, researchers analyzed data from an ongoing study of aging that involved nearly 8,800 participants who were an average of 66 years old. They was given tests that measured blood pressure, cholesterol levels and body mass index (BMI), and were also asked about their smoking habits. Participants were also tested for their risks for stroke and heart disease, and were given tasks that helped measure their memory and cognitive abilities after four and eight-year follow-up periods.

All of these risk factors had some effort on increased cognitive decline but across the board, only smoking was associated with lower performance on all cognitive measures studied at four and eight-year intervals.