***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: BACKGROUND Dietary n-3 polyunsaturated fatty acids improve brain functioning in animal studies , but there is limited study of whether this type of fat protects against Alzheimer disease . OBJECTIVE To examine whether fish consumption and intake of different types of n-3 fatty acids protect against Alzheimer disease . DESIGN Prospect i ve study conducted from 1993 through 2000 , of a stratified r and om sample from a geographically defined community . Participants were followed up for an average of 3.9 years for the development of Alzheimer disease . PATIENTS A total of 815 residents , aged 65 to 94 years , who were initially unaffected by Alzheimer disease and completed a dietary question naire on average 2.3 years before clinical evaluation of incident disease . MAIN OUTCOME MEASURES Incident Alzheimer disease diagnosed in a structured neurologic examination by means of st and ardized criteria . RESULTS A total of 131 sample participants developed Alzheimer disease . Participants who consumed fish once per week or more had 60 % less risk of Alzheimer disease compared with those who rarely or never ate fish ( relative risk , 0.4 ; 95 % confidence interval , 0.2 - 0.9 ) in a model adjusted for age and other risk factors . Total intake of n-3 polyunsaturated fatty acids was associated with reduced risk of Alzheimer disease , as was intake of docosahexaenoic acid ( 22:6n-3 ) . Eicosapentaenoic acid ( 20:5n-3 ) was not associated with Alzheimer disease . The associations remained unchanged with additional adjustment for intakes of other dietary fats and of vitamin E and for cardiovascular conditions . CONCLUSION Dietary intake of n-3 fatty acids and weekly consumption of fish may reduce the risk of incident Alzheimer disease 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 Exogenous estrogen use may lower risk of dementia in postmenopausal women . A relationship between long-term exposure to endogenous estrogens and incident dementia has been hypothesized but not studied . OBJECTIVE To determine whether a longer reproductive period , as an indicator of longer exposure to endogenous estrogens , is associated with lower risk of dementia and Alzheimer disease ( AD ) in women who have natural menopause . DESIGN AND SETTING The Rotterdam Study , a population -based prospect i ve cohort study conducted in the Netherl and s. PARTICIPANTS A total of 3601 women aged 55 years or older who did not have dementia at baseline ( 1990 - 1993 ) and had information on age at menarche , age at menopause , and type of menopause .  Participants were reexamined in 1993 - 1994 and 1997 - 1999 and were continuously monitored for development of dementia . MAIN OUTCOME MEASURES Incidence of dementia , based on Diagnostic and Statistical Manual of Mental Disorders , Revised Third Edition criteria , and AD , based on National Institute of Neurological Disorders and Stroke/Alzheimer 's Disease and Related Disorders Association criteria , compared by quartiles of reproductive period among women with natural menopause . RESULTS During 21 046 person-years of follow-up ( median follow-up , 6.3 years ) , 199 women developed dementia  , including 159 who developed AD . After adjusting for age , dementia was not clearly associated with length of reproductive period . However , after adjusting for multiple covariates , women with natural menopause and more reproductive years had an increased risk of dementia ( adjusted rate ratio [ RR ] for women with > 39 reproductive years [ highest quartile ] compared with < 34 reproductive years [ lowest quartile ] , 1.78 ; 95 % confidence interval [ CI ] , 1.12 - 2.84 ) . The adjusted RR per year of increase was 1.04 ( 95 % CI , 1.01 - 1.08 ) . For risk of AD , the adjusted RRs were 1.51 ( 95 % CI , 0.91 - 2.50 ) and 1.03 ( 95 % CI , 1.00 - 1.07 ) , respectively . Risk of dementia associated with a longer reproductive period was most pronounced in APOE epsilon4 carriers ( adjusted RR for > 39 reproductive years compared with < 34 reproductive years , 4.20 [ 95 % CI , 1.97 - 8.92 ] for dementia and 3.42 [ 95 % CI , 1.51 - 7.75 ] for AD ) , whereas in noncarriers , no clear association with dementia or AD was observed . CONCLUSION Our findings do not support the hypothesis that a longer reproductive period reduces risk of dementia in women who have natural menopause BACKGROUND Few prospect i ve studies have assessed diabetes mellitus as a risk factor for incident  Alzheimer disease ( AD ) and decline in cognitive function . OBJECTIVE To evaluate the association of diabetes mellitus with risk of AD and change in different cognitive systems . DESIGN Longitudinal cohort study . PARTICIPANTS For up to 9 years , 824 older ( those > 55 years ) Catholic nuns , priests , and brothers underwent detailed annual clinical evaluations .  MAIN OUTCOME MEASURES Clinical ly diagnosed AD and change in global and specific measures of cognitive function . RESULTS Diabetes mellitus was present in 127 ( 15.4 % ) of the participants . During a mean of 5.5 years of observation , 151 persons developed AD . In a proportional hazards model adjusted for age , sex , and educational level , those with diabetes mellitus had a 65 % increase in the risk of developing AD compared with those without diabetes mellitus ( hazard ratio , 1.65 ; 95 % confidence interval , 1.10 - 2.47 ) . In r and om effects models , diabetes mellitus was associated with lower levels of global cognition , episodic memory , semantic memory , working memory , and visuospatial ability at baseline . Diabetes mellitus was associated with a 44 % greater rate of decline in perceptual speed ( P = .02 ) , but not in other cognitive systems . CONCLUSIONS Diabetes mellitus may be associated with an increased risk of developing AD and may affect cognitive systems differentially Objective To investigate whether plasma interleukin-6 ( IL-6 ) is cross-sectionally related to poorer cognitive function and whether a baseline plasma IL-6 measurement can predict risk for decline in cognitive function in longitudinal follow-up of a population -based sample of nondisabled elderly people . Methods A prospect i ve cohort study of 779 high-functioning men and women aged 70 to 79 from the MacArthur Study of Successful Aging was conducted . Regression modeling was used to investigate whether baseline IL-6 levels ( classified by tertiles ) were associated with initial cognitive function and whether IL-6 levels predicted subsequent declines in cognitive function from 1988 to 1991 ( 2.5-year follow-up ) and from 1988 to 1995 ( 7-year follow-up ) . Results Subjects in the highest tertile for plasma IL-6 were marginally more likely to exhibit poorer baseline cognitive function ( i.e. , scores below the median ) , independent of demographic status , social status , health and health behaviors , and other physiologic variables ( odds ratio [ OR ] = 1.46 ; 95 % CI : 0.97 , 2.20 ) . At 2.5 years , those in both the second tertile of IL-6 ( OR = 2.21 ; 95 % CI : 1.44 , 3.42 ) and the third tertile ( OR = 2.03 ; 95 % CI : 1.30 , 3.19 ) were at increased risk of cognitive decline even after adjusting for all confounders . At 7 years of follow-up , only those in the highest IL-6 tertile were significantly more likely to exhibit declines in cognition ( OR = 1.90 ; 95 % CI : 1.14 , 3.18 ) after adjustment for all confounders . Conclusions The results suggest a relationship between elevated baseline plasma IL-6 and risk for subsequent decline in cognitive function . These findings are consistent with the hypothesized relationship between brain inflammation , as measured here by elevated plasma IL-6 , and neuropathologic disorders Background : Moderate alcohol drinking is suggested to be beneficial for cognitive functions , but the results of previous studies have varied greatly . Little is known about the effects of midlife alcohol drinking on the cognitive functions later in life . Methods : Participants were derived from r and om , population -based sample s studied in Eastern Finl and in 1972 , 1977 , 1982 , or 1987 . A total of 1,341 participants were reexamined in 1998 , after an average follow-up period of 21 years , at ages 65–79 years . Results : The participants who did not drink alcohol at midlife had a poorer performance in episodic memory , psychomotor speed , and executive function in late life as compared with infrequent and frequent drinkers , adjusted for sociodemographic and vascular factors . Also late-life nondrinkers had poorer psychomotor speed and executive function . These findings were evident especially among nonsmokers . Further , no interactions between apolipoprotein E4 and alcohol or sex and alcohol were found . Conclusions : Alcohol drinking both at midlife and later is favorably related to the function in several cognitive domains , including episodic memory , psychomotor speed , and executive function , in late life . However , it is not clear whether the association is causal , what is the possible mechanism , and what would be a safe limit of drinking for the best cognitive function Although many studies have found a cross-sectional relation between depression and dementia or depressive symptomatology and cognitive functioning , the direction of the association is still unknown . The purpose of this analysis was to determine whether high depressive symptomatology is predictive of cognitive deterioration among the elderly 3 years later . Data came from a community-based prospect i ve cohort study of noninstitutionalized and nondemented subjects aged 65 years and over living in the Gironde department in southwest France ( 1,600 subjects were interviewed at both study entry in 1989 and 3-year follow-up ) . Cognitive functions were assessed with the  Mini-Mental State Examination ( MMSE )  , and cognitive deterioration was defined as an MMSE score decrease of at least five points between two assessment s. The Center for Epidemiologic Studies Depression ( CES-D ) Scale was used to evaluate the level of depressive symptomatology . The present study reports that a high level of depressive symptomatology is not predictive of cognitive deterioration 3 years later ( relative risk = 0.8 , 95 % confidence interval 0.3 - 2.1 ) . The authors observed that the risk of cognitive deterioration was associated with the concomitant level of depressive symptomatology at the 3-year follow-up , independent of depressive symptoms at entry . These results indicate that the association between high depressive symptomatology and poor cognitive functioning is cross-sectional , and they illustrate the importance of adjusting for depressive symptomatology in epidemiologic studies assessing cognitive functions Studies of disability in old age have focused on gross measures of physical functioning 
    Output:
    
The meta- analysis shows a moderate association between obesity and the risks for dementia and AD .