According to researchers people who smoke a pack of cigarette daily and manage to survive to middle age are prone to a significant decline in their cognitive abilities.
The study was started in 1946, when researchers decided to track around 5,362 children born in the same week of March. The participants underwent 21 check-ups during the follow-up period. The last check-up was conducted when the participants reached the age of 53 years.
During the check-ups participants were made to do a verbal memory test (in which the participants were read a list of 15 words and then asked to write as many as they could remember) and a visual search test (in which the participants were given a page of random letters and made to mark all the P and W alphabets they could find in one minute).
The results of the check-up showed that the participants (between ages 43-53) who smoked had a rapid decline in memory and also a poor performance in the visual search test. The visual search skills had slowed down by 43 years of age. According to researchers all these effects were seen mainly on those who smoked more than 20 cigarettes a day.
According to the researchers, the participants (smokers) were not allowed to smoke during the check-up, so by the time they performed the tests they had not smoked for at least one and a half hours. So it is possible that the decline in performance was due to a state of nicotine withdrawal in smokers.