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 homocystei ne, 'thermolabile' methylenetetrahydrofolatereductase (MTHFR) genotype, B v itamin status and measures of renal function in elderly (70-89 years) and n onagenarian (90 + years) subjects, with the hypothesis that octo/nonagenari an 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 (geometri c mean [GM]) for all elderly subjects. Intriguingly, homocysteine was signi ficantly lower in 90 + (GM; 8.2 mu mol/l) compared to 70-89-year-old subjec ts (GM; 9.8 mu mol/l) despite significantly lower glomerular filtration rat e (GFR) and serum B12 in nonagenarian subjects and comparable MTHFR thermol abile (TT) genotype frequency, folate and B6 status to 70-89-year-olds. For all elderly subjects, the odds ratio and 95% confidence intervals for plas ma 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 < 14 0 umol/l and 2.1 (1.0-4.4) for male sex. This study shows that plasma homoc ysteine does not invariably increase with age. Compared to similarly enlist ed 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, suggestin g that lower homocysteine may be associated with survival. (C) 2000 Elsevie r Science Ireland Ltd. All rights reserved.