***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: 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 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 CONTEXT Data regarding the association between sub clinical hypothyroidism and cardiovascular disease outcomes are conflicting among large prospect i ve cohort studies . This might reflect differences in participants ' age , sex , thyroid-stimulating hormone ( TSH ) levels , or preexisting cardiovascular disease . OBJECTIVE To assess the risks of coronary heart disease ( CHD ) and total mortality  for adults with sub clinical hypothyroidism . DATA SOURCES AND STUDY SELECTION The data bases of MEDLINE and EMBASE ( 1950 to May 31 , 2010 ) were search ed without language restrictions for prospect i ve cohort studies with baseline thyroid function and subsequent CHD events , CHD mortality , and total mortality . The reference lists of retrieved articles also were search ed . DATA EXTRACTION Individual data on 55,287 participants with 542,494 person-years of follow-up between 1972 and 2007 were supplied from 11 prospect i ve cohorts in the United States , Europe , Australia , Brazil , and Japan . The risk of CHD events was examined in 25,977 participants from 7 cohorts with available data . Euthyroidism was defined as a TSH level of 0.50 to 4.49 mIU/L. Sub clinical hypothyroidism was defined as a TSH level of 4.5 to 19.9 mIU/L with normal thyroxine concentrations . RESULTS Among 55,287 adults , 3450 had sub clinical hypothyroidism ( 6.2 % ) and 51,837 had euthyroidism . During follow-up , 9664 participants died ( 2168 of CHD ) , and 4470 participants had CHD events ( among 7 studies ) . The risk of CHD events and CHD mortality increased with higher TSH concentrations . In age- and sex-adjusted analyses , the hazard ratio ( HR ) for CHD events was 1.00 ( 95 % confidence interval [ CI ] , 0.86 - 1.18 ) for a TSH level of 4.5 to 6.9 mIU/L ( 20.3 vs 20.3/1000 person-years for participants with euthyroidism ) , 1.17 ( 95 % CI , 0.96 - 1.43 ) for a TSH level of 7.0 to 9.9 mIU/L ( 23.8/1000 person-years ) , and 1.89 ( 95 % CI , 1.28 - 2.80 ) for a TSH level of 10 to 19.9 mIU/L ( n = 70 events/235 ; 38.4/1000 person-years ; P < .001 for trend ) . The corresponding HRs for CHD mortality were 1.09 ( 95 % CI , 0.91 - 1.30 ; 5.3 vs 4.9/1000 person-years for participants with euthyroidism ) , 1.42 ( 95 % CI , 1.03 - 1.95 ; 6.9/1000 person-years ) , and 1.58 ( 95 % CI , 1.10 - 2.27 , n = 28 deaths/333 ; 7.7/1000 person-years ; P = .005 for trend ) . Total mortality was not increased among participants with sub clinical hypothyroidism . Results were similar after further adjustment for traditional cardiovascular risk factors . Risks did not significantly differ by age , sex , or preexisting cardiovascular disease . CONCLUSIONS Sub clinical hypothyroidism is associated with an increased risk of CHD events and CHD mortality in those with higher TSH levels , particularly in those with a TSH concentration of 10 mIU/L or greater OBJECTIVE Recently , it has been repeatedly shown that patients with sub clinical hypothyroidism ( SH ) formerly considered as completely symptom free , may have numerous minimal , often non-specific subjective complaints , and that in those patients it is possible to prove many subtle but objective deviations . We decided to quantify whether there are event related potential ( ERP ) deviations as electrophysiological markers of cognitive activity in patients with SH and whether ERP could be influenced by thyroxine treatment leading to normalization of TSH level in serum . SUBJECTS AND DESIGN  Event related potential ( ERP )  was examined in thirty one patients ( mean age 52 + /- 12.5 years ) with SH and without any other endocrine or metabolic diseases and in 29 subjects of the control group . From 31 patients 20 women ( mean age 61.8 + /-6.8 years ) were selected and divided into a group of 10 women treated six months with L-thyroxine until the normalization of TSH and remaining 10 women receiving placebo . ERP examination  was repeated and all such patients also underwent neuropsychological examination consisting of the Wechsler Memory Scale and the MMPI/100 ( Minnesota Multiphasic Personality Inventory ) . The interval between the diagnosis of SH and final evaluation of treatment was 16 months . RESULTS In SH thyroxine treated patients the average P3 wave latency was 374 ms ( SD 40.6 ) , while in placebo group it was 340 ms ( SD 32.3 . P<0.01 ) . In addition , the treatment with thyroxine normalized the TSH level result ed in a decrease of P3 wave latency from 374 + /- 36.3 ms to 343 + /- 16.3 ms ( P<0.01 ) . However , in the placebo group such changes were not observed , the latency of P3 being 387 + /- 24.3 ms at the beginning and 379 + /- 36.5 ms at the end of observation period . No significant correlations between P3 wave latency and thyroid parameters were found . In thyroxine treated group a significant improvement in verbal memory ( P<0.01 ) , visual memory ( P<0.01 ) and 
    Output:
    
This meta- analysis demonstrates a relationship between sHT and cognitive impairment only in individuals younger than 75 years of age and those with higher TSH concentrations .
No correlation was found while considering all the studies as a whole .
The lack of utilization of age-related serum TSH reference ranges and consequent potential misdiagnosis of sHT in older people may account for this