Endogenous subclinical thyroid disorders, physical and cognitive function, depression, and mortality in older individuals.

OBJECTIVE: To what extent endogenous subclinical thyroid disorders contribute to impaired physical and cognitive function, depression, and mortality in older individuals remains a matter of debate.
DESIGN: A population-based, prospective 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 subclinical hypothyroidism and 34 (2.8%) individuals had subclinical hyperthyroidism. Compared with euthyroidism (n=1121), subclinical hypo-, and hyper-thyroidism were not significantly associated with impairment of physical or cognitive function, or depression. On the contrary, participants with subclinical 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. Subclinical 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 subclinical thyroid disorders on physical or cognitive function, depression, or mortality in an older population.