We report on 194 individuals (96 men and 98 women), aged 65 and
over, who had dementia assessments and basal TSH measurements as
part of an ongoing epidemiological study of dementing disorders in
a larger population. Dementia was diagnosed according to DSM-III-R
and measured by the Clinical Dementia Rating scale; CDR scores of
0, 0.5, and > or = 1, represent individuals with no dementia (n =
122), possible dementia (n = 29), and definite dementia (n = 43),
respectively. The odds ratio for the association of elevated TSH
with definite dementia (CDR > or = 1) was 3.8 (95% confidence
interval = 1.6, 9.1) and with possible and/or definite dementia
(CDR > or = 0.5) was 3.8 (95% confidence interval = 1.6, 9.2),
after adjusting for the effects of age, gender, and level of
education. This is the first community-based study to report an
association between TSH elevation and dementia. Our findings are
consistent with recent evidence that subclinical hypothyroidism is
associated with cognitive impairment, and that thyroidal state may
influence cerebral metabolism.