Seasonal variation of serum vitamin D and the effect of vitamin D supplementation in Irish community-dwelling older people.
Age Ageing
; 40(2): 168-74, 2011 Mar.
Article
em En
| MEDLINE
| ID: mdl-21051444
ABSTRACT
BACKGROUND:
Ireland is at 53°N, and its population risk of vitamin D deficiency is high. Previous Irish studies suggested a significant seasonality of serum 25-hydroxyvitamin D [25(OH)D] and a beneficial effect of supplementation in raising 25(OH)D levels. However, in Irish older people, little is known about the magnitude of the supplementation effect and whether supplementation affects 25(OH)D seasonality.DESIGN:
cross-sectional observational.SETTING:
outpatient clinic.SUBJECTS:
five hundred and forty-six community-dwelling subjects (mean age 73.0, SD 7.4; 68.5% females) were assessed between September 2007 and May 2009.METHODS:
for supplemented and non-supplemented 'cosinor' analysis (Pulse_XP®) of monthly 25(OH)D. Period global solar radiation (GSR) and solar elevation angle (SEA) data were collected as proxy markers of ultraviolet-B radiation exposure. Multivariate linear regression was conducted to investigate the independent effect of GSR and SEA on 25(OH)D, controlling for confounders.RESULTS:
supplemented group (N = 183) 89.1% were on cholecalciferol 800 IU/day. Mean 25(OH)D = 64.1 (95% confidence interval 52.2-75.8) nmol/l, with no significant seasonality; regression neither GSR nor SEA predicted 25(OH)D. Non-supplemented group (N = 363) mean 25(OH)D = 40.3 (35.5-45.0) nmol/l, with significant seasonality (55.5% variance remaining), peak in August, amplitude = 6.0 (3.1-8.8) nmol/l; regression both GSR (P = 0.002) and the interaction GSR * SEA (P = 0.018) predicted 25(OH)D.CONCLUSIONS:
vitamin D supplementation was associated with a mean serum 25(OH)D increase of 23.8 nmol/l. Interestingly, supplementation seemed to blunt seasonality. In the supplemented group, 72.1% had individual 25(OH)D levels below the recommended 75 nmol/l. There is a case for universal supplementation in Irish older people, probably at a higher dose. Further research is needed to establish the optimum dose.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Estações do Ano
/
Luz Solar
/
Vitamina D
/
Deficiência de Vitamina D
/
Colecalciferol
/
Suplementos Nutricionais
/
Vida Independente
Tipo de estudo:
Etiology_studies
/
Observational_studies
/
Prevalence_studies
/
Prognostic_studies
/
Risk_factors_studies
Limite:
Aged
/
Aged80
/
Female
/
Humans
/
Male
País/Região como assunto:
Europa
Idioma:
En
Revista:
Age Ageing
Ano de publicação:
2011
Tipo de documento:
Article
País de afiliação:
Irlanda