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 micromol/l
(geometric mean [GM]) for all elderly subjects. Intriguingly, homocysteine was significantly
lower in 90+ (GM; 8.2 micromol/l) compared to 70-89-year-old subjects (GM; 9.8 micromol/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.