Concerns about risks for older people with vitamin B12 deficiency have delayed the introduction of mandatory folic acid fortification in the UK. We examined the risks of anaemia and cognitive impairment in older people with low B12 and high folate status in the setting of voluntary fortification in the UK. Data were obtained from two cross-sectional studies (n 2403) conducted in Oxford city and Banbury in 1995 and 2003, respectively. Associations (OR and 95 % CI) of cognitive impairment and of anaemia with low B12 status (holotranscobalamin < 45 pmol/l) with or without high folate status (defined either as serum folate >30 nmol/l or >60 nmol/l) were estimated after adjustment for age, sex, smoking and study. Mean serum folate levels increased from 15·8 (sd 14·7) nmol/l in 1995 to 31·1 (sd 26·2) nmol/l in 2003. Serum folate levels were greater than 30 nmol/l in 9 % and greater than 60 nmol/l in 5 %. The association of cognitive impairment with low B12 status was unaffected by high v. low folate status (>30 nmol/l) (OR 1·50 (95 % CI 0·91, 2·46) v. 1·45 (95 % CI 1·19, 1·76)), respectively. The associations of cognitive impairment with low B12 status were also similar using the higher cut-off point of 60 nmol/l for folate status ((OR 2·46; 95 % CI 0·90, 6·71) v. (1·56; 95 % CI 1·30, 1·88)). There was no evidence of modification by high folate status of the associations of low B12 with anaemia or cognitive impairment in the setting of voluntary fortification, but periodic surveys are needed to monitor fortification.
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