Cognitive Impairment Central Nervous System

long-term฀smoking฀OR฀=฀1.36;฀CI:฀1.03–1.80;฀smoking฀cessation฀had฀a฀discernible฀inlu- ence,฀but฀did฀not฀abolish฀the฀effect฀in฀comparison฀with฀non-smokers.฀To฀date,฀a฀direct฀cor- relation฀has฀been฀observed฀overall฀between฀smoking฀and฀cognitive฀information฀processing,฀ with฀smoking฀postulated฀to฀have฀a฀negative฀effect฀ [23] . However,฀this฀association฀is฀contested฀by฀the฀indings฀from฀a฀4฀year฀population-based฀ study฀ [24] . In฀a฀study฀of฀131฀children฀aged฀9–12฀years,฀postnatal฀secondhand฀smoke฀exposure฀has฀ been฀reported฀to฀be฀associated฀with฀reduced฀language฀ability฀measured฀using฀a฀language฀ score฀ [25] . There฀may฀also฀be฀negative฀effects฀on฀certain฀occupations฀with฀a฀high฀level฀of฀respon- sibility,฀e.g.฀pilots.฀In฀this฀respect,฀pilots฀who฀smoke,฀if฀obliged฀to฀abstain฀from฀nicotine฀ intake฀ during฀ light,฀ may฀ exhibit฀ certain฀ symptoms฀ leading฀ to฀ performance฀ decrement.฀ Giannakoulas฀et฀al.฀studied฀20฀healthy฀male฀aviators,฀who฀were฀regular฀smokers,฀mean฀ age฀ 33.7฀ ±฀ 1.4฀ year฀ operating฀ military฀ ixed-฀ and฀ rotary-wing฀ aircrafts฀ C-47฀ Dakota,฀ F-16,฀A.฀Bell฀205฀ [26] .฀The฀pilots฀were฀subjected฀to฀a฀12-h฀abstinence฀from฀cigarette฀ smoking,฀during฀which฀time฀they฀performed฀light฀duties.฀After฀landing,฀the฀intensity฀of฀the฀ nicotine฀withdrawal฀syndrome,฀as฀well฀as฀its฀effect฀on฀physiological฀parameters,฀psycho- logical฀functions฀and฀cognitive฀tasks฀were฀studied.฀The฀researches฀reported฀that฀the฀most฀ frequent฀ symptoms฀ reported฀ during฀ nicotine฀ deprivation฀ were฀ nervousness,฀ craving฀ for฀ tobacco,฀tension-฀anxiety,฀fatigue,฀dificulty฀in฀concentration,฀decrease฀in฀alertness,฀disor- ders฀of฀ine฀adjustments,฀prolonged฀reaction฀times,฀anger-irritability,฀drowsiness,฀increase฀ in฀appetite฀and฀impairment฀of฀judgement.฀It฀was฀concluded฀that฀an฀abrupt฀cessation฀of฀ smoking฀may฀be฀detrimental฀to฀light฀safety฀and฀the฀smoking฀withdrawal฀syndrome฀may฀ inluence฀lying฀parameters฀ [26] .

7.1.2 Influence on Cognitive Performance

Nicotine฀has฀been฀reported฀to฀enhance฀performance฀in฀tasks฀of฀selective฀attention฀ [27] .฀In฀this฀ context,฀eficient฀attentional฀iltering฀obviously฀depends฀on฀the฀successful฀inhibition฀of฀dis- tracting฀information.฀A฀larger฀negative฀priming฀effect฀was฀found฀in฀participants฀who฀had฀ smoked฀in฀comparison฀with฀those฀who฀sham-smoked.฀It฀is฀suspected฀that฀nicotine฀promotes฀ the฀iltering฀of฀distracting฀information,฀thus฀enhancing฀selective฀attention฀ [27] .฀Transdermal฀ nicotine฀patches฀have฀some฀of฀the฀same฀effects฀on฀performance฀and฀mood฀as฀cigarette฀smok- ing฀in฀that฀they฀produce฀a฀calming฀effect฀and฀a฀feeling฀of฀happiness,฀as฀well฀as฀improving฀ attentional฀processing฀and฀memory฀functions฀repetition฀of฀word฀lists฀ [28] .฀Nicotine฀improves฀ cognitive฀performance฀not฀only฀after฀smoking฀cessation,฀but฀also฀apparently฀in฀normal฀non- smoking฀subjects฀and฀in฀people฀with฀a฀variety฀of฀disease฀states฀e.g.฀Alzheimer’s฀disease,฀ children฀and฀adolescents฀with฀attention฀deicit฀hyperactivity฀disorder฀ADHD฀ [29,฀30] . According฀to฀other฀investigators,฀learning฀processes฀and฀attention฀are฀adversely฀affected,฀ although฀it฀is฀unclear฀whether฀these฀changes฀are฀due฀to฀perceptual฀or฀impaired฀motor฀aspects฀ of฀the฀tasks฀involved.฀Event-related฀potentials,฀reaction฀times฀and฀tests฀of฀working฀memory฀ word฀recognition฀were฀assessed฀in฀one฀study฀in฀order฀to฀elucidate฀this฀question.฀The฀smok- ers฀were฀tested฀in฀a฀“smoking”฀and฀a฀12฀h฀“deprived”฀condition.฀Smokers฀exhibited฀faster฀ reaction฀times฀for฀words฀occurring฀new฀in฀the฀tests,฀together฀with฀effects฀suggesting฀that฀ smoking฀ facilitates฀ processes฀ related฀ to฀ the฀ motor฀ output฀ aspects฀ of฀ working฀ memory.฀ During฀the฀12฀h฀enforced฀abstention฀from฀smoking,฀reaction฀times฀were฀delayed฀as฀also฀ found฀for฀non-smokers,฀with฀the฀result฀that฀nicotine฀may฀ultimately฀be฀assumed฀to฀promote฀ working฀memory฀ [20] . In฀contrast฀to฀smoking,฀nicotine฀4฀mg฀nicotine฀chewing฀gum฀inluences฀various฀EEG฀ components฀increased฀theta฀and฀alpha฀frequency,฀decreased฀delta฀power.฀However,฀nei- ther฀reaction฀times฀nor฀event-related฀brain฀potentials฀were฀changed,฀as฀has฀been฀reported฀ after฀cigarette฀smoking฀ [31] . The฀anxiolytic฀effects฀induced฀by฀smoking฀depend฀on฀the฀benign฀distraction฀of฀the฀smoker฀ [32] .฀Only฀those฀who฀smoked฀a฀cigarette฀with฀a฀high฀nicotine฀yield,฀paired฀with฀participation฀ in฀a฀distracting฀activity,฀experienced฀a฀reduction฀in฀anxiety.฀Those฀who฀smoked฀in฀the฀absence฀ of฀distraction฀even฀experienced฀an฀exacerbation฀of฀anxiety฀ [32] .฀These฀indings฀suggest฀that฀ nicotine฀–฀rather฀than฀the฀behavioural฀or฀sensory฀aspects฀of฀smoking฀–฀interacts฀with฀distrac- tion฀and฀leads฀to฀the฀alleviation฀of฀anxiety฀or฀apprehension฀ [32] .฀Under฀laboratory฀conditions,฀ in฀contrast,฀nicotine฀tends฀to฀display฀anxiogenic฀activity฀ [33] . Smokers’฀reactions฀to฀a฀lexical฀decision-making฀test฀decision฀as฀to฀whether฀or฀not฀a฀ sequence฀of฀letters฀represents฀a฀word฀were฀also฀faster฀and฀more฀complete฀than฀those฀of฀ placebo฀cigarette฀smokers฀ [34] .฀According฀to฀other฀data,฀while฀cigarette฀smoking฀has฀no฀ negative฀effect฀upon฀performance฀for฀simple฀perceptual฀tasks฀smoking฀was฀found฀to฀exert฀ measurable฀negative฀effects฀upon฀performance฀for฀more฀complex฀information฀processing฀ tasks฀ [35] .฀The฀residual฀effects฀of฀smoking฀consist฀primarily฀of฀retardation฀of฀cognitive฀ processes฀in฀older฀adults฀ [36] ,฀whereas฀this฀negative฀effect฀is฀not฀observed฀in฀ex-smokers฀ and฀non-smokers.฀In฀a฀comparison฀with฀placebo,฀visual฀information฀processing฀was฀also฀ increased฀under฀4฀mg฀nicotine฀gum฀and฀cigarette฀smoking,฀whereas฀self-reported฀feelings฀ of฀alertness฀and฀energy฀were฀assessed฀as฀higher฀while฀cigarette฀smoking฀than฀under฀4฀mg฀ nicotine฀gum฀ [37] . Memory฀list฀of฀20฀words฀was฀tested฀in฀smokers฀of฀cigarettes฀with฀different฀nicotine฀ yields.฀ Smokers฀ of฀ higher-yield฀ cigarette฀ brands฀ were฀ found฀ to฀ have฀ better฀ recall฀ than฀ smokers฀ of฀ lower-yield฀ brands฀ [38] .฀ When฀ performing฀ more฀ dificult฀ tasks,฀ adolescent฀ smokers฀altered฀their฀smoking฀behaviour฀by฀taking฀more฀puffs฀per฀cigarette฀and฀inhaling฀ more฀deeply.฀Women฀responded฀more฀than฀men฀to฀the฀concentration฀task฀ [39] .฀The฀effects฀ of฀smoking฀a฀low฀0.7฀mg฀and฀a฀middle฀nicotine฀yield฀1.3฀mg฀cigarette฀on฀learning฀and฀ retention฀were฀tested฀in฀undergraduate฀smokers฀ [40] .฀Both฀nicotine฀levels฀had฀an฀effect฀on฀ retention฀only,฀with฀task฀dificulty฀appearing฀to฀be฀of฀secondary฀relevance.฀Serial฀learning฀ data฀suggested฀that฀the฀effect฀is฀shown฀more฀on฀long-term฀than฀on฀short-term฀memory.

7.1.3 Intellectual Impairment in Childhood

Several฀studies฀indicate฀that฀intellectual฀development฀is฀impaired฀in฀children฀whose฀mothers฀ actively฀smoke฀during฀pregnancy฀and฀that฀this฀harmful฀effect฀is฀less฀pronounced฀in฀the฀chil- dren฀of฀passive฀smokers฀ [41,฀42] .฀Other฀confounding฀variables฀were฀also฀eliminated฀from฀the฀ psychological฀tests฀employed.฀Contradictory฀results฀have฀been฀found฀for฀cognitive฀and฀lan- guage฀ability฀ [43–45] .฀Children฀exposed฀to฀the฀harmful฀effects฀of฀tobacco฀smoke฀were฀found฀