Thyroid status and functional and cognitive status at baseline and survival after 3 years of follow-up: the OCTABAIX study.

OBJECTIVE: Subclinical thyroid disorders are common in older individuals. Health risks associated with subclinical 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, prospective 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 subclinical hypothyroidism and five (1.6%) had subclinical hyperthyroidism. Compared with euthyroid subjects (n=280; 91.8%), subclinical 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 subclinical 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.