Smoking can lessen IQ, thinking ability: study (Reuters) Updated: 2005-10-25 06:22
The poorer mental function seen among alcoholics, many of whom also regularly
smoke cigarettes, may be partially due to the long-term effects of nicotine, new
research suggests.
"People who are also smokers are at a much higher risk," Dr. Jennifer M.
Glass, of the University of Michigan's Addiction Research Center, told Reuters
Health.
In her study, "cigarette smoking was negatively related to IQ and thinking,"
she said.
This finding may seem counterintuitive, since many smokers attest to feeling
more alert and focused after smoking. Indeed, research shows that improved
mental functioning is one of the immediate effects of nicotine exposure. Chronic
smoking, however, is known to have the opposite effect.
Studies show that up to 87 percent of alcoholics smoke cigarettes, compared
to less than 30 percent of the general United States population. Yet, few
studies have looked into cigarette smoking as a factor that might explain the
cognitive deficits reported among alcoholics.
To investigate that association, Glass and her colleagues examined brain
function among 172 men from the same community, including 103 men who abused
alcohol.
The team found that men with higher scores on the lifetime alcohol problems
scale (LAPS) and those who reported a higher number of pack-years of smoking
(i.e. packs of cigarettes smoked per day times number of years) both had lower
IQ scores and lower scores on a test of global proficiency.
The proficiency test took into account the speed and accuracy with which the
men were able to perform on a battery of tests including those that measured
short-term memory, verbal reasoning and mathematical reasoning.
Upon further investigation, the researchers found that smoking predicted
poorer global proficiency even more strongly than alcoholism did. Their findings
were published online before publication in Drug and Alcohol Dependence.
Smoking also appeared to be independently associated with weaker verbal and
visual-spatial reasoning, the study indicates.
Thus, though smoking did not account for all of the decreased neurocognitive
functioning observed among the alcohol abusers, it did seem to account for some
of the effects, the report indicates.
The reason for the observed associations is unknown, and the researchers did
not investigate the "cause and effect story," Glass said, but she speculated
that the diminished cognitive ability among smokers may be partly due to some
mechanism involving a restricted flow of blood and oxygen to the brain.
Based on the current report, Glass said, "if you need another reason to quit
smoking, it's a good potential one to add to the list."
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