[Thyroid function, activities of daily living and survival in extreme old age: the 'Leiden 85-plus Study']

To determine the relationship between differences in thyroid function, changes in the activities of daily living and survival in the extremely-old segment of the general population in order to see whether screening for and treatment of subclinical thyroid-function disorders in the elderly will have a positive effect.

Prospective observational population study among 85-year-olds.

As part of the 'Leiden 85-plus Study', all persons were followed who had their 85th birthday during the period from 1 September 1997 to 31 August 1999 (average length of time followed: 3.7 years; SD: 1.4). There were 558 participants. The thyroid function of these subjects was determined and the limitations in the activities of daily living, depressive symptoms, cognitive function and mortality were recorded annually.

At the age of 85, there was no relation between the serum levels of thyroid-stimulating hormone (TSH) or free thyroxine (FT4) and limitations in the activities of daily living, the occurrence of depressive symptoms and cognitive deterioration. Neither was any relationship found during the period of follow-up. A higher TSH-level was associated with a lower mortality, even after correction for the differences in performance and health during the base measurement (mortality risk: 0.77 per SD-increase in TSH; 95% CI: 0.63-0.94). The mortality risk per SD-increase in FT4 was 1.16 (95% CI: 1.04-1.30).

From the age of 85, there was no relationship between thyroid function and limitations in the activities of daily living, the occurrence of depressive symptoms or a deterioration in cognitive functions. Moreover, elderly persons with a less active thyroid gland lived longer. This raises the question whether the screening for and treatment of subclinical thyroid-function disorders in persons of extreme old age, as recommended, will have any positive effects.