***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Abstract Rationale : Recent research suggests that chewing gum may improve aspects of cognitive function and mood . There is also evidence suggesting that chewing gum reduces stress . It is important , therefore , to examine these two areas and to determine whether context ual factors ( chewing habit , type of gum , and personality ) modify such effects . Objectives : The aims of the present study were : ( i ) to determine whether chewing gum improved mood and mental performance ; ( ii ) to determine whether chewing gum had benefits in stressed individuals ; and ( iii ) to determine whether chewing habit , type of gum and level of anxiety modified the effects of gum . Subjects and methods : A cross-over study involving 133 volunteers was carried out . Each volunteer carried out a test session when they were chewing gum and without gum , with order of gum conditions counterbalanced across subjects . Baseline sessions were conducted prior to each test session . Approximately half of the volunteers were tested in 75 dBA noise ( the stress condition ) and the rest in quiet . Volunteers were stratified on chewing habit and anxiety level . Approximately , half of the volunteers were given mint gum and half fruit gum . The volunteers rated their mood at the start and end of each session and had their heart rate monitored over the session . Saliva sample s were taken to allow cortisol levels ( good indicator of alertness and stress ) to be assayed . During the session , volunteers carried out tasks measuring a range of cognitive functions ( aspects of memory , selective and sustained attention , psychomotor speed and accuracy ) . Results : Chewing gum was associated with greater alertness and a more positive mood . Reaction times were quicker in the gum condition , and this effect became bigger as the task became more difficult . Chewing gum also improved selective and sustained attention . Heart rate and cortisol levels were higher when chewing which confirms the alerting effect of chewing gum . Conclusions : Overall , the results suggest that chewing gum produces a number of benefits that are generally observed and not context -dependent . In contrast to some previous research , chewing gum failed to improve memory . Further research is now required to increase our knowledge of the behavioral effects of chewing gum and to identify the underlying mechanisms RATIONALE Recent research has shown that even small doses ( < 40 mg ) of caffeine can improve alertness and increase performance efficiency on attention tasks . Previous studies have given the caffeine in a variety of beverages or in capsules and it was of interest to see whether similar effects could be observed when the caffeine was given in gum . In addition , chewing gum has been shown to have behavioural effects and the present study extended our knowledge of this topic . OBJECTIVES To compare the effects of caffeinated gum ( 40 mg ) , placebo gum and no gum conditions on mood and attention . METHODS A double blind placebo controlled study was conducted with volunteers being r and omly assigned to one of the three conditions . Baseline measures of mood and attention were taken prior to chewing and a test session was then conducted . One hundred and eighteen young adults participated in the study . RESULTS Caffeinated gum was associated with a more positive mood and better performance on tasks requiring sustained attention . The caffeine improved the speed of encoding of new information which is consistent with previous findings . Chewing placebo gum was also found to be associated with more positive mood , both shortly after chewing and at the end of the study . CONCLUSIONS The implication s of the present study are that chewing caffeinated gum has been shown to improve performance efficiency and mood by its alerting and energising effects . The profile of caffeine effects is what one would predict from the existing caffeine literature and such effects may be extremely beneficial in real-life situations . Prior chewing of placebo gum was associated with a more positive mood and this also confirms previous findings This study tests the hypothesis that chewing gum leads to cognitive benefits through improved delivery of glucose to the brain , by comparing the cognitive performance effects of gum and glucose administered separately and together . Participants completed a battery of cognitive tests in a fully related 2 x 2 design , where one factor was Chewing Gum ( gum vs. mint sweet ) and the other factor was Glucose Co-administration ( consuming a 25 g glucose drink vs. consuming water ) . For four tests ( AVLT Immediate Recall , Digit Span , Spatial Span and Grammatical Transformation ) , beneficial effects of chewing and glucose were found , supporting the study hypothesis . However , on AVLT Delayed Recall , enhancement due to chewing gum was not paralleled by glucose enhancement , suggesting an alternative mechanism . The glucose delivery model is supported with respect to the cognitive domains : working memory , immediate episodic long-term memory and language -based attention and processing speed . However , some other mechanism is more likely to underlie the facilitatory effect of chewing gum on delayed episodic long-term memory Chewing has been shown to alleviate feelings of sleepiness and improve cognitive performance during the day . This study investigated the effect of chewing on alertness and cognitive performance across one night without sleep as well as the possible mediating role of cardiac autonomic activity . Fourteen adults participated in a r and omized , counterbalanced protocol employing a chewing , placebo and caffeine condition . Participants completed tasks assessing psychomotor vigilance , tracking , grammatical reasoning , alertness and sleepiness each hour across the night . All participants received either placebo or caffeine ( 200 mg ) , while the chewing condition also chewed on a tasteless and odorless substance for 15 min each hour . Heart rate ( HR ) , root mean square of the successive differences in R-R intervals on the ECG ( RMSSD ) , and preejection period ( PEP ) were simultaneously recorded . Alertness and cognitive performance amongst the chewing condition did not differ or were in fact worse when compared with placebo . Similarly , measures of HR and RMSSD remained the same between these two conditions ; however , PEP was reduced in the later part of the night in the chewing condition compared with a relative increase for placebo . Caffeine led to improved speed and accuracy on cognitive tasks and increased alertness when compared with chewing .  Relative increases in RMSSD and reductions in HR were demonstrated following caffeine ; however , no change in PEP was seen . Strong associations between cardiac parasympathetic activity and complex cognitive tasks , as well as between subjective alertness and simpler cognitive tasks , suggest a differential process mediating complex versus simple cognitive performance during sleep deprivation The present study aim ed to examine the psychosomatic effect in the chewing of marketed gum  using electroencephalogram ( EEG ) as an index . The EEG were taken in two sets : ( i ) a resting period before chewing ( control recording ) and a resting record ( post-resting recording ) for examining reproducibility ; and ( ii ) a control recording and resting period after gum-chewing for 3 min ( post-chewing recording ) . The ratio of each frequency b and to the total frequency power , the mean frequency of the alpha b and and laterality of the frequency power was calculated . In the examination of the reproducibility , no statistically significant differences were observed between control recording and post-resting recording in all indices . In the reflection of EEG after gum-chewing , there were no significant differences between control recording and the post-chewing recording . However , a significant interaction was observed among these indices by analysis of variance . In addition , the alpha power in the post-chewing recording was significantly higher than that in the control recording at almost all the positions . In conclusion , the intra-individual reproducibility of EEG was confirmed in the recording method . Furthermore , it was suggested that a significant interaction and a rising trend of the mean frequency of the alpha b and after gum-chewing reflected ' arousal ' psychosomatic responses by the chewing of marketed gum OBJECTIVES To investigate the relationship between periodontal disease and cognitive decline .  DESIGN Analysis of a prospect i ve cohort study . SETTING The Health , Aging and Body Composition ( Health ABC ) Study . PARTICIPANTS One thous and fifty-three participants who were administered the Modified Mini-Mental State Examination ( 3MS )  at Year 1 ( baseline ) and Year 3 and had participated in a comprehensive periodontal examination at Year 2 . MEASUREMENTS The prospect i ve association between a range of oral health parameters and cognitive function was examined . Decline in 3MS score from Year 3 to 5 was investigated in 947 ( 89.9 % ) participants . Covariates included age , sex , education , race , cardiovascular disease and risk , and depressive symptoms . RESULTS Most indicators of adverse oral health at Year 2 were associated with cognitive impairment based on averaged 3MS scores less than 80 for Years 1 and 3 , but education and race substantially confounded these associations . Higher gingival index , a measure of gingival inflammation , at Year 2 remained independently associated with this definition of cognitive impairment and , in fully adjusted analyses , was also an independent predictor of a more-than-5-point cognitive decline from Year 3 to 5 . CONCLUSION Periodontitis may be a risk factor for cognitive decline . Gingivitis is reversible , and periodontitis to some degree is preventable and controllable when manifest . Therefore , further research is needed to clarify potential underlying mechanisms and oral health interventions that might ameliorate cognitive decline CognitiveDrug Research Ltd.,ReadingRG301EA , UKMany people chew gum partly due to the belief that itincreases aspects of mental performance , including concen-tration . To the best of our knowledge no empirical evidence exists to support this contention . The present experiment , therefore , examined the effects of chewing gum using acomprehensive and sensitive cognitive assessment battery and two tasks manipulating cognitive load . Heart rateresponses were also measured . Seventy-five healthy adult participants ( mean age 246years ) were r and omly assigned to one of three experimentalconditions ( N‹25 per group ) : ‘ ‘ chewing ’ ’ – a piece of sugar-free chewing gum ( Wrigley ’s Extra Spearmint ) was chewednaturally and constantly throughout the procedure ; ‘ ‘ shamchewing ’ ’ – participants mimicked chewing movements in theabsence of gum ; ‘ ‘ quiet control ’ ’ – no chewing behaviour wasperformed . Aspects of attention , working memory and long-termmemory were assessed using the Cognitive Drug Research ( CDR ) computerised battery . Stimuli were presented on acolour monitor and , except for two written word recall tasks , responses were collected automatically using a ‘ ‘ Yes’’/‘‘No’’responsemodule . Thetaskswerepresentedintheorder : Wordpresentation , Immediate Word Recall , Picture Presentation , SimpleReactionTime , DigitVigilance , ChoiceReactionTime , Spatial Working Memory , Numeric Working Memory , Delayed Word Recall , Word Recognition and PictureRecognition ( for details , e.g. see Kennedy et al. 2000).Following the CDR battery , participants performed compu-terised Serial Subtractions tasks . These assess concentration and working memory and allow manipulation of cognitiveload ( see Scholey et al. , 2001 for details ) . In the present study SerialThrees(involvingtherepeatedsubtractionofthreefroma r and omly generated starting number using the computer’snumerickeypad)thenSerialSevens(subtractionofseven)wereused , each for 2min . Eachcognitive task outcome measurewasanalysedby one-way analysis ofvariance , withDunnettcomparisonstoisolatebetween-group effects where appropriate . The most strikingfindingwasasignificanteffectonbothimmediate and delayedword recall , with more words being recalled in the chewingconditioncomparedwiththequietcontrolcondition(Table1).The Spatial Working Memory sensitivity index and Numericworkingmemoryreactiontimeweresimilarlyimprovedinthechewingcondition , and alsointheshamchewingconditionforthe latter measure ( which reflects the efficiency of workingmemory operations ) . In addition , simple reaction times wereslowerintheshamchewingconditionthaninthequietcontrolcondition . Baseline heart rate recordings ( sample d at 30-s intervals)began 240s prior to treatment and continued during a 180-speriod of chewing , sham chewing or sitting quietly prior tocognitive assessment ( which lasted about 30min in all ) . Heartrate ( mean bpm ) was calculated during baseline , treatment , each of the 10 CDR tasks and both Serial Subtraction tasks .  Heart rate changes relative to baseline were subjected to a3(Condition ) 14(Phase ) factorial ANOVA with repeated measures on the latter factor . The main effect of conditionapproached significance , F(2,936)‹30 , p‹006 ; heart ratesweresignificantlyhigherinthechewingconditionthaninquietcontrols , p<005 ( Fig. 1 ) . There was also a significant maineffect oftask , F(13,936)‹130,p<001:with theexceptionofSimple Reaction Time and Delayed Word Recall , all taskphasesofthe study wereassociatedwithsignificantincreasesinheart rate . There was also a significant task conditioninteraction , F(26,936)‹256 , p<001.These results providedthefirst evidence thatthechewingofgum can improve episodic memory ( involving the learning , storage and retrieval of information ) and working memory(where information is held ‘ ‘ on line ’ ’ ) . They did not indicatethat gum-chewing improves aspects of attention , at least asmeasured here . The impaired Simple Reaction Time during sham chewingmay reflect diversion of attentional re sources during initialstages of performing this unfamiliar behaviour . This is con-sistent with the elevated heart rate observed while shamchewing in earlierphases of the experiment ( Fig. 1 ) . Althoughanactivecontrolisimportant , shamchewingmaynotbeidealfor this purpose , because most cognitive scores ( except , nota-E-mail : a.scholey@unn.ac.uk bly , Numeric Working Memory Reaction Time ) in this group0195–6663/02/$ – see front matter # 2002 Elsevier Science Ltd. All rights reserved The notion that chewing gum may relieve stress was investigated 
    Output:
    
These effects also appeared with improvement in mood and stress relief and were influenced by time-on-task effect .
Further studies are needed , but chewing could be useful for modifying cognitive function