Vitamin B12 deficiency affects 5-20% of older adults, with up to 40% with low B12 levels [<260pmol/L]. The risk of B12 deficiency increases with age. Vitamin B12 is essential for neurological function, and B12 deficiency is a known cause of clinical neuropathy and has been associated with cognitive impairment. However, little is known about the relationship between low B12 levels and peripheral nerve function and information processing speed, cross-sectionally or longitudinally, in older adults. The purpose of this dissertation is to examine whether low B12 levels or change in B12 levels were associated with peripheral nerve function or information processing speed. We examined whether low B12 or high homocysteine [≥13µmol/L] and 3-year change in B12 and homocysteine was associated with 6-year change in peripheral nerve function or neurological signs in older Italian adults from the InCHIANTI Study. We found high homocysteine was associated with lower nerve conduction amplitude and greater inability to detect 4g monofilament. In the Health ABC Study, we studied whether low [<260pmol/L] or deficient [<260pmol/L & methylmalonic acid [MMA] >271nmol/L & MMA>2-methylcitrate] B12 were associated with peripheral sensory and motor nerve function, and evaluated whether there was a threshold effect of serum B12 levels on peripheral nerve function in older black and white adults. We found poor B12 were associated with greater insensitivity to 1.4g monofilament and worse nerve conduction velocity [NCV] and there was a significant serum B12 threshold level of 390 pmol/L for NCV. To consider cognitive function, we examined whether low B12 or 7-year change in B12 were associated with decline in Digit Symbol Substitution Test [DSST] scores over 6-years. We found low B12 was associated with greater DSST decline and a serum B12 level of 410 pmol/L was associated with lower DSST decline. These results have important public health significance, because low B12 levels, above clinical deficiency [<148 pmol/L], were associated with worse peripheral nerve function and decline in information processing speed, which may lead to decreased cognitive and physical function, and disability in older adults. Vitamin B12 supplementation is widely available, adequately absorbed, well-tolerated, and potentially may prevent declines in neurological function.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-04052011-131438 |
| Date | 29 June 2011 |
| Creators | Leishear, Kira |
| Contributors | Anne B. Newman, Luigi Ferrucci, Stephanie A. Studenski, Caterina Rosano, Elsa S. Strotmeyer, Robert M. Boudreau |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-04052011-131438/ |
| Rights | restricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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