Community-living nonagenarians in Northern Ireland have lower plasma homocysteine but similar methylenetetrahydrofolate reductase thermolabile genotype prevalence compared to 70-89-year-old subjects

This cross-sectional study assessed relationships between plasma homocysteine, 'thermolabile' methylenetetrahydrofolatereductase (MTHFR) genotype, B vitamin status and measures of renal function in elderly (70-89 years) and nonagenarian (90 + years) subjects, with the hypothesis that octo/nonagenarian subjects who remain healthy into old age as defined by 'Senieur' status might show reduced genetic or environmental risk factors usually associated with hyperhomocysteinaemia. Plasma homocysteine was 9.1 mu mol/l (geometric mean [GM]) for all elderly subjects. Intriguingly, homocysteine was significantly lower in 90 + (GM; 8.2 mu mol/l) compared to 70-89-year-old subjects (GM; 9.8 mu mol/l) despite significantly lower glomerular filtration rate (GFR) and serum B12 in nonagenarian subjects and comparable MTHFR thermolabile (TT) genotype frequency, folate and B6 status to 70-89-year-olds. For all elderly subjects, the odds ratio and 95% confidence intervals for plasma homocysteine being in the highest versus lowest quartile was 4.27 (2.04-8.92) for age < 90 compared > 90 years, 3.4 (1.5-7.8) for serum folate < 10.7 compared > 10.7nmol/l, 3.0 (0.9-10.2) for creatinine > 140 compared < 140 umol/l and 2.1 (1.0-4.4) for male sex. This study shows that plasma homocysteine does not invariably increase with age. Compared to similarly enlisted 70-89-year-olds, apparently well, mentally alert, community-living 90 + year olds approximating 'Senieur' status, show lower homocysteine, which is unexplained by renal function, TT genotype and B vitamin status, suggesting that lower homocysteine may be associated with survival. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.