Subclinical hypothyroidism and cognitive dysfunction in the elderly

While overt hypothyroidism is associated with reversible dementia in the elderly, the relationship of subclinical hypothyroidism with cognition remains a controversial issue. Our aim was to investigate the correlation between subclinical hypothyroidism and cognition in the elderly, with particular reference to long term memory and selective attention. We selected 337 outpatients (177 men and 160 women), mean age 74.3 years, excluding the subjects with thyroid dysfunction and those treated with drugs influencing thyroid function. The score of Mini Mental State Examination (MMSE) was significantly lower in the group of patients with subclinical hypothyroidism than in euthyroid subjects (p<0.03). It was observed that patients with subclinical hypothyroidism had a probability about 2 times greater (RR = 2.028, p<0.05) of developing cognitive impairment. Prose Memory Test (PMT) score resulted significantly lower in subjects with subclinical hypothyroidism (p<0.04). Considering the Matrix Test (MT) score, the performance was slightly reduced in subclinical hypothyroidism (NS). Furthermore, TSH was negatively correlated with MMSE (p<0.04), PMT (p<0.05) and MT score (NS). No correlation was found between FT4 and FT3 and MMSE, PMT and MT score. In the elderly, subclinical hypothyroidism is associated with cognitive impairment, and its impact on specific aspects of cognition (long term memory and selective attention) is less evident.