Abstract
The ε4 allele of apolipoprotein E (APOE), and the plasma levels of APOE, amyloid β-protein precursor, amyloid β1-40 (Aβ40) and homocysteine (Hcy) have all been correlated with the presence of dementia. Mutations in the methylnetetrahydrofolate reductase enzyme (MTHFR) have been associated with elevated levels of Hcy. This study explored the association of these factors with cognition and depression in community dwelling older men.
Two hundred and ninety-nine men, mean age 78.9 years (SD 2.8), were studied in this cross-sectional survey. Mean plasma Hcy was 13.5 (SD 5.3) μmol/L. The MTHFR genotype had no obvious impact on Hcy levels. Ln Hcy and Ln Aβ40 were both inversely correlated with calculated glomerular filtration rate (cGFR), r = -0.41 (p < 0.001) and r = -0.28 (p < 0.001), respectively. There was a positive correlation between Ln Hcy and Ln Aβ40, r = 0.19 (p < 0.001), which remained significant after adjusting for cGFR, with a doubling of Hcy associated with a 24% increase of Aβ40. The e4 allele was associated with increased depressive symptoms as measured by the Geriatric Depression Scale-15, Odds ratio (OR) = 2.59 (95%CI 1.06–6.34) and poorer performance on the Clock Drawing Test, OR = 2.32 (95% CI: 1.25–4.29).
There was a positive association between Aβ40 and Hcy, even after adjustment for cGFR in this sample of well, community dwelling older men. This association may help elucidate the link between elevated levels of Hcy and Alzheimer's disease.