***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: 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 BACKGROUND AND OBJECTIVE The original Whlckham Survey documented the prevalence of thyroid disorders in a r and omly selected sample of 2779 adults which matched the population of Great Britain in age , sex and social class . The aim of the twenty‐year follow‐up survey was to determine the Incidence and natural history of thyroid disease in this cohort 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 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 Sub clinical hypothyroidism ( SCH ) and cognitive dysfunction are both common in the elderly and have been linked . It is important to determine whether T4 replacement therapy in SCH confers cognitive benefit . OBJECTIVE Our objective was to determine whether administration of T4 replacement to achieve biochemical euthyroidism in subjects with SCH improves cognitive function . DESIGN AND SETTING We conducted a double-blind placebo-controlled r and omized controlled trial in the context of United Kingdom primary care . PATIENTS Ninety-four subjects aged 65 yr and over ( 57 females , 37 males ) with SCH were recruited from a population of 147 identified by screening . INTERVENTION T4 or placebo was given at an initial dosage of one tablet of either placebo or 25 microg T4 per day for 12 months . Thyroid function tests were performed at 8-weekly intervals with dosage adjusted in one-tablet increments to achieve TSH within the reference range for subjects in treatment arm . Fifty-two subjects received T4 ( 31 females , 21 males ; mean age 73.5 yr , range 65 - 94 yr ) ; 42 subjects received placebo ( 26 females , 16 males ; mean age 74.2 yr , 66 - 84 yr ) . MAIN OUTCOME MEASURES Mini-Mental State Examination , Middlesex Elderly Assessment of Mental State ( covering orientation , learning , memory , numeracy , perception , attention , and language skills ) , and Trail-Making A and B were administered . RESULTS Eighty-two percent and 84 % in the T4 group achieved euthyroidism at 6- and 12-month intervals , respectively . Cognitive function scores at baseline and 6 and 12 months were as follows : Mini-Mental State Examination T4 group , 28.26 , 28.9 , and 28.28 , and placebo group , 28.17 , 27.82 , and 28.25 [ not significant ( NS ) ] ; Middlesex Elderly Assessment of Mental State T4 group , 11.72 , 11.67 , and 11.78 , and placebo group , 11.21 , 11.47 , and 11.44 ( NS ) ; Trail-Making A T4 group , 45.72 , 47.65 , and 44.52 , and placebo group , 50.29 , 49.00 , and 46.97 ( NS ) ; and Trail-Making B T4 group , 110.57 , 106.61 , and 96.67 , and placebo group , 131.46 , 119.13 , and 108.38 ( NS ) . Linear mixed-model analysis demonstrated no significant changes in any of the measures of cognitive function over time and no between-group difference in cognitive scores at 6 and 12 months . CONCLUSIONS This RCT provides no evidence for treating elderly subjects with SCH with T4 replacement therapy to improve cognitive function 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 Sub- clinical hypothyroidism ( SCH ) is a common disorder . People with this condition may have symptoms which could affect their perception of health . Therefore , the perceived health status of people with SCH was assessed and compared with population -matched norms . DESIGN A prospect i ve cross-sectional survey . METHODS Seventy-one adults with SCH , age range 18 - 64 years were studied .  Perceived health status was measured by the  Short Form-36 ( SF-36 ) version 2 question aire  , which has been vali date d in a UK population setting . The SF-36 has eight scales measuring physical functioning , role physical , bodily pain , general health , vitality , social functioning , role emotional and mental health . Their SF-36 scores were compared with UK normative data after matching for age and sex and are reported as z-scores . RESULTS Scores of all eight SF-36 scales were significantly lower in people with SCH compared with the normative population . A negative score ( compared with zero of the normative population ) indicates worse health status . The most significantly impaired aspects of health status were vitality and role limitations due to physical problems ( role physical scale ) with 
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In addition , prospect i ve analysis including four studies showed pooled ES of 0.033 ( 95 % CI -0.001 - 0.067 ) for MMSE ( I ( 2 ) < 0.001 % ) , indicating that sub clinical hypothyroidism was not significantly associated with accelerated cognitive decline .
This systematic review and meta- analysis provides no evidence that supports an association between SCH and cognitive impairment in relatively healthy older adults