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Thursday, September 13, 2012

Don't Inhale: Researchers Warn Second-Hand Smoke Can Damage Memory

Those exposed forget 1 out of every 5 things their unexposed peers would recall

Northumbria University, located near Newcastle in the Northeastern coast of England, has produced a cautionary study warning that second-hand smoke may lead to memory loss.

Published [abstract] in the peer-reviewed journal Addiction, the work by Psychologists Drs. Tom Heffernan and Terence O'Neil compared 27 second-hand smokers (SHS), 27 current-smokers (CS), and 29 non-second-hand smokers (non-SHS).  Participants were subjected to the Cambridge Prospective Memory Test (CAMPROMPT), a common memory test.  The researchers took into consideration age, other drug use, mood, and IQ, in an effort to narrow the correlation down to smoke inhalation or lack thereof.

Current smokers fared the worst on the test, recalling approximately 25-30 percent less than their non-exposed peers in time- and event-based tasks.  But somewhat more surprising, the researchers also observed a time-based memory gap in those exposed to second-hand smoke.  They recalled over 15 percent less than their non-exposed peers.  Interestingly, memory was not affected in event-based tasks.

The authors conclude:

In a sample of never-smoked  adults,  exposure  to SHS is associated  with increased  time- based, but  not  event-based  objective  PM  impairments  when  compared  with  a  Non-SHS group, but not to the same level of impairments as observed in current smokers. Given the concerns raised by the World Health Organisation in relation to the global impact of current smoking and exposure to SHS upon a range of health measures and other indices this is a topic that is of major public interest. Despite this, there is little in the way of systematic study on what impact exposure SHS has on everyday remembering, with the findings presented here representing the first in this line of research.

At an applied level, the findings from the present study  could  be  incorporated  into  campaigns  that  alert  people  to  the  dangers  of exposure  to SHS beyond  health  indices  and highlighting  the  everyday  cognitive consequences of such exposure. Clearly the findings from this exploratory study could be integrated into such initiatives.

The second-hand smokers in the study were exposed to, on average, 25 hours a week (3.6 hr. per day) for 4 and 1/2 years.

As with other studies on drug abuse, it's important to note that the observed phenomena was merely a correlation -- how exactly smoke affects the brain is very poorly understood, beyond basic reward circuitry.

There are many compelling questions raised by the study.  The biggest is how exactly the memory impairment works on a neurological level.  Another major question is whether so-called "third-hand" smoke -- smoke absorbed by a building occupied by a heavy smoker -- could have a similar, but smaller affect.  Some studies have suggested that this may be the case with other smoking-related health issues.

Alcohol has been linked to similar memory impairment (though recent studies rebuke the hypothesis of brain cell death).  However, there is no second-hand analogy with alcohol.  On the other hand marijuana has been linked to short-term memory loss.  Given the poor understanding of second-hand (tobacco) smoke and memory loss with tobacco (the NU paper claims to be the first study on the topic), the impact of second-hand marijuana smoke is likely poorly misunderstood.

Smoking has been linked to many adverse health affects. [Image Source: Reuters / Alexandra Beier]

In addition to memory affects, previous studies have shown a link between tobacco smoking and brain damage.  Another study indicated smoking reduced brain activity in teens.  Tobacco has also been linked to a variety of cancers, including testicular cancer.  Habitually smoking marijuana also showed a clear correlation with certain kinds of testicular cancer.

It's clear that you should be careful what you inhale -- there is compelling evidence that it could damage your memory or cause other adverse affects, though researchers in some cases aren't sure quite how that process occurs.

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