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dc.contributor.advisorSkidmore, Paula
dc.contributor.advisorGearry, Richard B.
dc.contributor.authorStrydom, Andrea
dc.date.available2015-02-20T00:13:38Z
dc.date.copyright2015
dc.identifier.citationStrydom, A. (2015). Mild cognitive impairment associated with higher serum 25-hydroxyvitamin D levels in a middle aged population living at a moderately high latitude in New Zealand (Thesis, Master of Science). University of Otago. Retrieved from http://hdl.handle.net/10523/5467en
dc.identifier.urihttp://hdl.handle.net/10523/5467
dc.description.abstractObjective: The association between serum 25-hydroxyvitamin D (s25OHD) concentrations and cognitive function has been investigated in only a few studies of middle aged adults (40-60 years); with inconsistent results found. The main objective of this Canterbury-based study was to examine the association between s25OHD levels and mild cognitive impairment (MCI) in participants in their early fifties, while adjusting for a number of confounders. The secondary objective was to assess if this association would differ when stratified by gender. Design: Cross-sectional study participants, 366 adults aged 49-53 years living within the Canterbury District Health Board region from the Canterbury Health, Aging and Life Course study, were divided into two cognitive function groups: MCI and normal cognitive function (NCF). A score of <26 on the Montreal Cognitive Assessment test was defined as MCI and NCF was defined as a score ≥26 out of 30. Logistic regression was used to investigate the relationship between the cognitive function groups (outcome variable) and two s25OHD groups: insufficient s25OHD (≤50 nanomoles per litre (nmol/L)) and sufficient s25OHD (>50 nmol/L). Age, gender, education, ethnicity, annual household income, body mass index, depression, season of blood draw, alcohol intake, current smoking status, serum intact parathyroid hormone, serum creatinine, general health, vitamin D food intake, calcium food intake, vitamin D supplement use and chronic diseases were considered as potential confounders. Results: In the univariate and multivariate logistic regression with cognitive function as the binary outcome variable (MCI (n=89) and NCF (n=277)) and vitamin D as a continuous predictor variable, the results did not reach statistical significance (crude odds ratio (OR) 1 (0.99, 1.01) p=0.306, adjusted OR 0.99 (0.98, 1.00) p=0.084). However, an inverse association between s25OHD levels and cognitive function were observed in the univariate and multivariate logistic regression with vitamin D as a categorical variable. Compared to those with MCI, participants with NCF belonged more often to the insufficient s25OHD group (≤50 nmol/L, n=124) than the sufficient s25OHD group (>50 nmol/L, (n=242)) (crude OR 0.52 (0.30, 0.89) p=0.020, adjusted OR 0.44 (0.24, 0.79) p=0.008). In the analyses stratified by gender, the effect observed was similar, however, the association reached statistical significance only for female participants (adjusted OR 0.43 (0.18, 0.94) p=0.041) and not for male participants (adjusted OR 0.48 (0.18, 1.19) p=0.127). Further adjusted for vitamin D supplement use and season, did not change the effect size, however was just statistically significant, for female participants (adjusted OR 0.43 (0.17, 0.99) p=0.053). Conclusions: Those with MCI belonged more often to the s25OHD group >50 nmol/L than the s25OHD group ≤50 nmol/L in a middle aged community-dwelling cohort, mostly for women, and appeared to be due to vitamin D supplement use. However, causality cannot be concluded due to the cross-sectional design of this study.
dc.format.mimetypeapplication/pdf
dc.language.isoen
dc.publisherUniversity of Otago
dc.rightsAll items in OUR Archive are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.
dc.subjectCognition
dc.subjectCognitive function
dc.subjectVitamin D
dc.subjectserum 25-hydroxyvitamin D
dc.subjectMild cognitive function
dc.subjectmidlife
dc.subjectmiddle-aged
dc.subjectNew Zealand
dc.subjectCanterbury
dc.titleMild cognitive impairment associated with higher serum 25-hydroxyvitamin D levels in a middle aged population living at a moderately high latitude in New Zealand
dc.typeThesis
dc.date.updated2015-02-19T23:31:59Z
dc.language.rfc3066en
thesis.degree.disciplineHuman Nutrition
thesis.degree.nameMaster of Science
thesis.degree.grantorUniversity of Otago
thesis.degree.levelMasters
otago.openaccessOpen
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