***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 
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    ***EXAMPLES*** 
    Input: We investigated the prospect i ve relationship between thyroid status and the risk of dementia and Alzheimer 's disease among a r and om sample of 1843 participants , aged 55 years and over , from the population ‐based prospect i ve Rotterdam Study OBJECTIVE Sub clinical thyroid disorders are common in older individuals . Health risks associated with sub clinical hypothyroidism in older adults are unclear . The aim of the study is to evaluate whether thyroid status in elderly subjects correlates with physical and cognitive function at baseline and with 3-year mortality . DESIGN A population -based , prospect i ve cohort of the OCTABAIX study ( 307 inhabitants aged 85 years at baseline ) . METHODS Chronic drug prescription , functional status ( Barthel and Lawton indices ) and cognitive status according to the Spanish version of the Mini-Mental State Examination were recorded . Quality of life was assessed using the visual analogue scale of the quality of life test . Concentrations of TSH and thyroxine  were measured . Participants were classified in accordance with clinical categories of thyroid function . RESULTS Twenty ( 6.5 % ) individuals had sub clinical hypothyroidism and five ( 1.6 % ) had sub clinical hyperthyroidism . Compared with euthyroid subjects ( n=280 ; 91.8 % ) , sub clinical hypo- and hyperthyroidism subjects were not significantly associated with poor physical or cognitive function at baseline . Fifty-one ( 15.1 % ) subjects died during the 36 months of follow-up . TSH values and sub clinical hypo- and hyperthyroidism were not associated with an increased overall mortality risk ( hazard ratio ( HR ) 1.086 , 95 % CI 0.987 - 1.196 and HR 0.905 , 95 % CI 0.902 - 1.053 respectively ) . CONCLUSIONS This study does not support the association of TSH or thyroid disorders with physical or cognitive function at baseline or with 3-year mortality in the oldest old subjects OBJECTIVE To what extent endogenous sub clinical thyroid disorders contribute to impaired physical and cognitive function , depression , and mortality  in older individuals remains a matter of debate . DESIGN A population -based , prospect i ve cohort of the Longitudinal Aging Study Amsterdam . METHODS TSH and , if necessary , thyroxine and triiodothyronine levels were measured in individuals aged 65 years or older . Participants were classified according to clinical categories of thyroid function . Participants with overt thyroid disease or use of thyroid medication were excluded , leaving 1219 participants for analyses . Outcome measures were physical and cognitive function , depressive symptoms ( cross-sectional ) , and mortality ( longitudinal ) RESULTS Sixty-four ( 5.3 % ) individuals had sub clinical hypothyroidism and 34 ( 2.8 % ) individuals had sub clinical hyperthyroidism . Compared with euthyroidism ( n=1121 ) , sub clinical hypo- , and hyper-thyroidism were not significantly associated with impairment of physical or cognitive function , or depression . On the contrary , participants with sub clinical hypothyroidism did less often report more than one activity limitation ( odds ratio 0.44 , 95 % confidence interval ( CI ) 0.22 - 0.86 ) . After a median follow-up of 10.7 years , 601 participants were deceased . Sub clinical hypo- and hyper-thyroidism were not associated with increased overall mortality risk ( hazard ratio 0.89 , 95 % CI 0.59 - 1.35 and 0.69 , 95 % CI 0.40 - 1.20 respectively ) . CONCLUSIONS This study does not support disadvantageous effects of sub clinical thyroid disorders on physical or cognitive function , depression , or mortality in an older population Background : It is unclear whether in late life serum thyroid-stimulating hormone ( TSH ) predicts risk of developing cognitive impairment . Objective : This study investigated the prospect i ve relationship of serum TSH with the risk of developing  mild cognitive impairment ( MCI ) , Alzheimer ’s disease ( AD ) and vascular dementia ( VaD ) in an elderly cohort with a 4-year follow-up . Methods : Data are for 660 subjects aged 65 years and older from an Italian population -based cohort who were cognitively normal at an extensive assessment in 1999/2000 and underwent follow-up assessment in 2003/2004 .  Serum TSH was measured at baseline . Multinomial logistic models adjusted for sociodemographic and cardiovascular risk factors were used to investigate the association of serum TSH ( both as a tertile and continuous log-transformed variable ) with risk of incident MCI , AD and VaD diagnosed according to international criteria . Results : Over 3.8 ± 0.7 years of follow-up , there were 149 incident MCI cases ( 77 with impairment of memory and 72 with impairment of nonmemory domains ) and 86 incident dementia cases ( 53 with AD , 28 with VaD ) . No association between baseline TSH and risk of developing any MCI subtype or AD was found . The highest TSH tertile had a threefold higher increased risk of VaD ( OR : 3.25 , 95 % CI : 1.01–10.77 , p = 0.048 ) compared to the lowest tertile . Risk of VaD increased about 60 % for each 1 SD increase in log-transformed TSH ( OR : 1.61 , 95 % CI : 1.06–2.44 , p = 0.025 ) . Conclusions : In this elderly cohort , baseline TSH was not related to the risk of developing MCI or AD , but high TSH was associated with an increased risk of VaD. These results suggest further need for research using larger sample s to examine the role of TSH as a predictor of VaD and the role of thyroid autoimmunity in vascular cognitive impairment Neuroanatomical connections point to possible interactions between areas influencing energy homeostasis and those influencing cognition . We assessed whether serum leptin , thyroxine , and thyroid stimulating hormone ( TSH ) levels are associated with and interact to influence cognitive performance among US adults . Data from the National Health and Nutrition Examination Survey III ( 1988 - 1994 ) were used . Measures included a  battery of neuropsychological tests and serum leptin , thyroxine , and TSH levels  ( 20 - 59-year-old : n = 1114 - 2665 ; 60 - 90-year-old : n = 1365 - 5519 ) . Among those 20 - 59-year-old , the middle tertile of leptin ( vs. first tertile ) was inversely related to the number of errors on the symbol digits substitution test . Increased thyroxine level was associated with a poorer performance on the serial digits test in the 20 - 59-year-old , but a better performance on the math test in 60 - 90-year-old group . TSH was associated with poor performance on various tests in the 20 - 59-year-old , but better performance in the 60 - 90-year-old group . Significant antagonistic interactions were found in both age groups between thyroxine , TSH , and leptin for a number of tests , including between leptin and thyroxine in the 60 - 90-year-old group in their association with word recall-correct score . We found significant associations of our main exposures with cognitive function among US adults , going in opposite directions between age groups in the cases of thyroid hormonal levels , as well as some interactive effects between exposures . It is important to conduct prospect i ve cohort studies to provide further insight into potential interventions that would assess interactive effects of various hormonal replacement regimens Thyroid dysfunction is associated with cognitive impairment and dementia , including Alzheimer 's disease ( AD ) . It remains unclear whether thyroid dysfunction results from , or contributes to , Alzheimer pathology . We determined whether thyroid function is associated with dementia , specifically AD , and Alzheimer-type neuropathology in a prospect i ve population -based cohort of Japanese-American men .  Thyrotropin , total and free thyroxine were available in 665 men aged 71 - 93 years and dementia-free at baseline ( 1991 ) , including 143 men who participated in an autopsy sub- study . During a mean follow-up of 4.7 ( S.D. : 1.8 ) years , 106 men developed dementia  of whom 74 had AD . Higher total and free thyroxine levels were associated with an increased risk of dementia and AD ( age and sex adjusted hazard ratio ( 95 % confidence interval ) per S.D. increase in free thyroxine : 1.21 ( 1.04 ; 1.40 ) and 1.31 ( 1.14 ; 1.51 ) , respectively ) . In the autopsied sub- sample , higher total thyroxine was associated with higher number of neocortical neuritic plaques and neurofibrillary tangles . No associations were found for thyrotropin . Our findings suggest that higher thyroxine levels are present with Alzheimer clinical disease and neuropathology Background Sub clinical thyroid dysfunction has been implicated as a risk factor for cognitive decline in old age , but results are inconsistent . We investigated the association between sub clinical thyroid dysfunction and cognitive decline in the PROspect i ve Study of Pravastatin in the Elderly at Risk ( PROSPER ) . Methods Prospect i ve longitudinal study of men and women aged 70–82 years with pre-existing vascular disease or more than one risk factor to develop this condition ( N = 5,154 ) . Participants taking antithyroid medications , thyroid hormone supplementation and /or amiodarone were excluded .  Thyroid function was measured at baseline : sub clinical hyper- and hypothyroidism were defined as thyroid stimulating hormones ( TSH ) < 0.45 mU/L or > 4.50 mU/L respectively , with normal levels of free thyroxine ( FT4 ) . Cognitive performance was tested at baseline and at four subsequent time points during a mean follow-up of 3 years , using five neuropsychological performance tests . Results Sub clinical hyperthyroidism and hypothyroidism were found in 65 and 161 participants , respectively . We found no consistent association of sub clinical hyper- or hypothyroidism with altered cognitive performance compared to euthyroid participants on the individual cognitive tests . Similarly , there was no association with rate of cognitive decline during follow-up . Conclusion We found no consistent evidence that sub clinical hyper- or hypothyroidism contribute to cognitive impairment or decline in old age . Although our data are not in support of treatment of sub clinical thyroid dysfunction to prevent cognitive dysfunction in later life , only large r and omized controlled trials can provide definitive evidence IMPORTANCE An association of clinical and sub clinical hypothyroidism with  mild cognitive impairment ( MCI )  has not been established . OBJECTIVE To evaluate the association of clinical and sub clinical hypothyroidism with MCI in a large population -based cohort . DESIGN , SETTING , AND PARTICIPANTS A cross-sectional , population -based study was conducted in Olmsted County , Minnesota . R and omly selected participants were aged 70 to 89 years on October 1 , 2004 , and were without documented prevalent dementia [ CORRECTED ] . A total of 2050 participants were evaluated and underwent in-person interview , neurologic evaluation , and neuropsychological testing  to assess performance in memory , attention/executive function , and visuospatial and language domains . Participants were categorized by consensus as being cognitively normal , having MCI , or having dementia according to published criteria . Clinical and sub clinical hypothyroidism were ascertained from a medical records linkage system . MAIN OUTCOMES AND MEASURES Association of clinical and sub clinical hypothyroidism with MCI . RESULTS Among 1904 eligible participants , the frequency of MCI was 16 % in 1450 individuals with normal thyroid function , 17 % in 313 persons with clinical hypothyroidism , and 18 % in 141 individuals with sub clinical hypothyroidism . After adjusting for covariates ( age , educational level , sex , apolipoprotein E ε4 , depression , diabetes mellitus , hypertension , stroke , body mass index , and coronary artery disease ) we found no significant association between clinical or sub clinical hypothyroidism and MCI ( odds ratio [ OR ] , 0.99 [ 95 % CI , 0.66 - 1.48 ] and 0.88 [ 0.38 - 2.03 ] , respectively ) . No effect of sex interaction was seen on these effects . In stratified analysis , the odds of MCI with clinical and sub clinical hypothyroidism among men was 1.02 ( 95 % CI , 0.57 - 1.82 ) and 1.29 ( 0.68 - 2.44 ) and , among women , was 1.04 ( 0.66 - 1.66 ) and 0.86 ( 0.37 - 2.02 ) , respectively . CONCLUSIONS AND RELEVANCE In this population -based cohort of elderly people , neither clinical nor sub clinical hypothyroidism was associated with MCI . Our findings need to be vali date d in a separate setting using the published criteria for MCI and confirmed in a longitudinal study CONTEXT The association between sub clinical hyperthyroidism and the risk of dementia has been vali date d in several 
    Output:
    
This meta- analysis supports that low thyrotropin level is significantly associated with an increased risk of Alzheimer ’s disease in the elderly