***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: CONTEXT Many observational studies have shown that physical activity reduces the risk of cognitive decline ; however , evidence from r and omized trials is lacking . OBJECTIVE To determine whether physical activity reduces the rate of cognitive decline among older adults at risk . DESIGN AND SETTING R and omized controlled trial of a 24-week physical activity intervention conducted between 2004 and 2007 in metropolitan Perth , Western Australia . Assessors of cognitive function were blinded to group membership . PARTICIPANTS We recruited volunteers who reported memory problems but did not meet criteria for dementia . Three hundred eleven individuals aged 50 years or older were screened for eligibility , 89 were not eligible , and 52 refused to participate . A total of 170 participants were r and omized and 138 participants completed the 18-month assessment . INTERVENTION Participants were r and omly allocated to an education and usual care group or to a 24-week home-based program of physical activity . MAIN OUTCOME MEASURE Change in Alzheimer Disease Assessment Scale-Cognitive Subscale ( ADAS-Cog ) scores ( possible range , 0 - 70 ) over 18 months . RESULTS In an intent-to-treat analysis , participants in the intervention group improved 0.26 points ( 95 % confidence interval , -0.89 to 0.54 ) and those in the usual care group deteriorated 1.04 points ( 95 % confidence interval , 0.32 to 1.82 ) on the ADAS-Cog at the end of the intervention . The absolute difference of the outcome measure between the intervention and control groups was -1.3 points ( 95 % confidence interval,-2.38 to -0.22 ) at the end of the intervention . At 18 months , participants in the intervention group improved 0.73 points ( 95 % confidence interval , -1.27 to 0.03 ) on the ADAS-Cog , and those in the usual care group improved 0.04 points ( 95 % confidence interval , -0.46 to 0.88 ) . Word list delayed recall and Clinical Dementia Rating sum of boxes improved modestly as well , whereas word list total immediate recall , digit symbol coding , verbal fluency , Beck depression score , and Medical Outcomes 36-Item Short-Form physical and mental component summaries did not change significantly . CONCLUSIONS In this study of adults with subjective memory impairment , a 6-month program of physical activity provided a modest improvement in cognition over an 18-month follow-up period . TRIAL REGISTRATION anzctr.org.au Identifier : ACTRN12605000136606 Objective : To study the influence of leisure activity participation on risk of development of  amnestic mild cognitive impairment ( aMCI ) .  Methods : The authors examined the relationship between baseline level of participation in leisure activities and risk of aMCI in a prospect i ve cohort of 437 community-residing subjects older than 75 years , initially free of dementia or aMCI , using Cox analysis adjusted for age , sex , education , and chronic illnesses . The authors derived  Cognitive and Physical Activity Scales based on frequency of participation in individual activities . Results : Over a median follow-up of 5.6 years , 58 subjects had development of aMCI . A one-point increase on the Cognitive ( hazard ratio [ HR ] 0.95 , 95 % CI 0.91 to 0.99 ) but not Physical Activities Scale ( HR 0.97 , 95 % CI 0.93 to 1.01 ) was associated with lower risk of aMCI . Subjects with Cognitive Activity scores in the highest ( HR 0.46 , 95 % CI 0.24 to 0.91 ) and middle thirds ( HR 0.52 , 95 % CI 0.29 to 0.96 ) had a lower risk of aMCI compared with subjects in the lowest third . The association persisted even after excluding subjects who converted to dementia within 2 years of meeting criteria for aMCI . Conclusions : Cognitive activity participation is associated with lower risk of development of amnestic mild cognitive impairment  , even after excluding individuals at early stages of dementia BACKGROUND Participation in leisure activities has been associated with a lower risk of dementia .  It is unclear whether increased participation in leisure activities lowers the risk of dementia or participation in leisure activities declines during the pre clinical phase of dementia . METHODS We examined the relation between leisure activities and the risk of dementia in a prospect i ve cohort of 469 subjects older than 75 years of age who resided in the community and did not have dementia at base line . We examined the frequency of participation in leisure activities at enrollment and derived  cognitive-activity and physical-activity scales in which the units of measure were activity-days per week . Cox proportional-hazards analysis was used to evaluate the risk of dementia according to the base-line level of participation in leisure activities , with adjustment for age , sex , educational level , presence or absence of chronic medical illnesses , and base-line cognitive status . RESULTS Over a median follow-up period of 5.1 years ,  dementia  developed in 124 subjects ( Alzheimer 's disease in 61 subjects , vascular dementia in 30 , mixed dementia in 25 , and other types of dementia in 8) . Among leisure activities , reading , playing board games , playing musical instruments , and dancing were associated with a reduced risk of dementia . A one-point increment in the cognitive-activity score was significantly associated with a reduced risk of dementia ( hazard ratio , 0.93 [ 95 percent confidence interval , 0.90 to 0.97 ] ) , but a one-point increment in the physical-activity score was not ( hazard ratio , 1.00 ) . The association with the cognitive-activity score persisted after the exclusion of the subjects with possible pre clinical dementia at base line . Results were similar for Alzheimer 's disease and vascular dementia . In linear mixed models , increased participation in cognitive activities at base line was associated with reduced rates of decline in memory . CONCLUSIONS Participation in leisure activities is associated with a reduced risk of dementia , even after adjustment for base-line cognitive status and after the exclusion of subjects with possible pre clinical dementia . Controlled trials are needed to assess the protective effect of cognitive leisure activities on the risk of dementia CONTEXT Evidence suggests that physical activity may be related to the clinical expression of dementia . Whether the association includes low-intensity activity such as walking is not known . OBJECTIVE To examine the association between walking and future risk of dementia in older men . DESIGN Prospect i ve cohort study . SETTING AND PARTICIPANTS Distance walked per day was assessed from 1991 to 1993 in 2257 physically capable men aged 71 to 93 years in the Honolulu-Asia Aging Study . Follow-up for incident dementia was based on neurological assessment at 2 repeat examinations ( 1994 - 1996 and 1997 - 1999 ) . MAIN OUTCOME MEASURES Overall dementia , Alzheimer disease , and vascular dementia . RESULTS During the course of follow-up , 158 cases of dementia were identified ( 15.6/1000 person-years ) . After adjusting for age , men who walked the least ( < 0.25 mile/d ) experienced a 1.8-fold excess risk of dementia compared with those who walked more than 2 mile/d ( 17.8 vs 10.3/1000 person-years ; relative hazard [ RH ] , 1.77 ; 95 % confidence interval [ CI ] , 1.04 - 3.01 ) . Compared with men who walked the most ( > 2 mile/d ) , an excess risk of dementia was also observed in those who walked 0.25 to 1 mile/d ( 17.6 vs 10.3/1000 person-years ; RH , 1.71 ; 95 % CI , 1.02 - 2.86 ) . These associations persisted after accounting for other factors , including the possibility that limited amounts of walking could be the result of a decline in physical function due to pre clinical dementia . CONCLUSIONS Findings suggest that walking is associated with a reduced risk of dementia . Promoting active lifestyles in physically capable men could help late-life cognitive function Relative risk among exposure groups in prospect i ve cohort studies is based on the assumption that all subjects are exposed at the level recorded at baseline throughout the study . Changes in risk behavior during follow-up will dilute the relative risk . This prospect i ve cohort study in Copenhagen , Denmark , between 1964 and 1994 included 30,640 men and women ; 19,149 were examined twice , with an interval of 6.7 ( st and ard deviation , 3.4 ) years .  Relative risks calculated from baseline measurements for moderately active and sedentary groups compared with the highly active group were 1.11 ( 95 % confidence interval : 1.05 , 1.18 ) and 1.64 ( 95 % confidence interval : 1.53 , 1.75 ) , respectively . The relative risk between the highly active group and the sedentary group decreased with increasing follow-up time . When intraindividual changes in physical activity level during follow-up were taken into account , the relative risk of physical inactivity was 24 - 59 % higher compared with the relative risk estimated from baseline measurements . The risk of a sedentary lifestyle is underestimated when it is calculated from one baseline measurement in prospect i ve studies , because subjects change behavior during follow-up Objective : This study evaluated the protective role of physical activity ( PA ) against  cognitive impairment ( CI ) in the oldest old ( age ≥ 85 ) . Method : Prospect i ve data on 66 optimally healthy , oldest old adults ( mean age 88.5 ) were analyzed using survival analysis . Results : In all , 12 men and 11 women reported exercising > 4 hours per week , and 38 participants developed CI ( mean onset age 93 ; mean follow-up 4.7 years ) . The effect of exercise was modified by gender . In more active women ( > 4 hours/week ) , the risk of CI was reduced by 88 % ( 95 % confidence interval 0.03 , 0.41 ) compared to those less active . Less active women had 2 times the incidence rate of CI compared to less active men and almost 5 times the rate compared to active women . Discussion : This study demonstrates the beneficial effects of exercise  on healthy brain aging even in the oldest old and emphasizes the importance of increasing PA in older women BACKGROUND Cognitive impairment that does not meet the criteria for dementia ( " Cognitive Impairment , No Dementia " -- CIND ) is a heterogeneous category with an increased risk of dementia . While greater physical activity is generally associated with a lower odds of both dementia and CIND , whether this effect applies across subgroups is not known . OBJECTIVES To investigate the association between physical activity and the risk of vascular CIND ( VCI-ND ) or mild cognitive impairment ( MCI ) . METHODS In the Canadian Study of Health and Aging community-dwelling cohort , of 4683 people who were not impaired at baseline , 3945 remained without cognitive impairment at 5 years , 454 were diagnosed with CIND , and 284 with dementia . Incident CIND and VCI-ND ( n=163 ) and MCI ( n=100 ) subtypes were investigated in relation to baseline physical activity , stratified by sex . RESULTS In women , moderate-high exercise was associated with a lower odds of CIND ( OR=0.62 , 95 % CI=0.46 - 0.84 ) and VCI-ND ( 0.34 , 0.18 - 0.63 ) relative to low exercise . There was no association for men or for MCI . CONCLUSION Exercise appears to reduce the risk of VCI-ND in women . Whether the lack of an effect of exercise on the odds of MCI reflects that ' prevented AD ' is indistinguishable from MCI is an intriguing possibility that merits further study CONTEXT Dementia is common , costly , and highly age related . Little attention has been paid to the identification of modifiable lifestyle habits for its prevention . OBJECTIVE To explore the association between physical activity and the risk of cognitive impairment and dementia .  DESIGN , SETTING , AND SUBJECTS Data come from a community sample of 9008 r and omly selected men and women 65 years or older , who were evaluated in the 1991 - 1992 Canadian Study of Health and Aging , a prospect i ve cohort study of dementia . Of the 6434 eligible subjects who were cognitively normal at baseline , 4615 completed a 5-year follow-up .  Screening and clinical evaluations were done at both waves of the study . In 1996 - 1997 , 3894 remained without cognitive impairment , 436 were diagnosed as having cognitive impairment-no dementia , and 285 were diagnosed as having dementia . MAIN OUTCOME MEASURE Incident cognitive impairment and dementia by levels of physical activity at baseline . RESULTS Compared with no exercise , physical activity was associated with lower risks of cognitive impairment , Alzheimer disease , and dementia of any type . Significant trends for increased protection with greater physical activity were observed . High levels of physical activity were associated with reduced risks of cognitive impairment ( age- , sex- , and education-adjusted odds ratio , 0.5 
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Conclusions : We conclude that there is evidence supporting the hypothesis that physical activity is likely to prevent the development of VaD , and should be highlighted as part of secondary prevention programmes in people at risk for cerebrovascular disease