A Prospective Study on the Development of Alzheimer's Disease with Regard to Thyroid-Stimulating Hormone and Homocysteine

Background/Aim: The combination of elevated total homocysteine (tHcy) levels and low levels of thyroid-stimulating hormone (TSH) are linked to Alzheimer's disease (AD) in some studies, although the evidence is mixed. Our objective was to prospectively investigate the association between tHcy and TSH and the subsequent development of AD. Methods: A subsample of 200 nondemented subjects was taken from the Kungsholmen Project, a population-based study among people 675 years. Information about tHcy and TSH levels were taken from the baseline investigation of the Kungsholmen Project study. Results: Increased tHcy levels were related to an elevated risk of AD (n = 61) after a mean follow-up time of 6.7 years. People with high tHcy (the 3rd tertile) had more than twice as high a risk of developing AD than those with low tHcy, even after adjusting for age, sex, education, ApoE status, MMSE score and laboratory parameters. tHcy was negatively correlated with TSH (p = 0.02). There was neither an influence of TSH nor an interaction between tHcy and TSH in the development of AD. Conclusions: These results suggest that homocysteine, but not TSH, is involved in the development of AD. The connection between elevated tHcy and low TSH levels needs to be studied further. Copyright (C) 2009 S. Karger AG, Basel