Association between serum 25-hidroxyvitamin D concentrations and ultraviolet index in Portuguese older adults: a cross-sectional study

Abstract

BackgroundThe older population is a risk group for hypovitaminosis D. The Ultraviolet Index (UVI) can be an indicator of potential for cutaneous synthesis of vitamin D but physiological and other environmental factors also influence vitamin D synthesis and status. Knowledge about vitamin D status in Portuguese older adults is limited. This study aims to explore the association between Ultraviolet Index and serum 25-hidroxyvitamin D3 [25(OH)D] levels accounting for other potential influential factors.MethodsA cross-sectional study was conducted between December 2015 and June 2016, in 1497 Portuguese older adults (≥ 65 years) within Nutrition UP 65 project. For each participant, serum 25(OH)D was determined and the mean UVI (mUVI) in the respective residence district was calculated for the previous 30 days. Stepwise linear regression analyses were conducted for the following periods of blood collection: between December and June, December and March and April and June. Standardized regression coefficients (Sβ) and 95% confidence intervals were calculated.ResultsThe median 25(OH)D concentration was 35.9 nmol/L. The UVI was independently and positively associated with 25(OH)D in the models for December–June (Sβ = 0.244, 95% CI: 0.198; 0.291, P < 0.001) and April–June (Sβ = 0.295, 95% CI: 0.299; 0.362, P < 0.001) and independently and negatively associated in December–March period (Sβ = −0.149, 95% CI: -0.211; −0.087, P < 0.001).ConclusionsIn this sample with high vitamin D deficiency frequency, the UVI was a predictor of 25(OH)D levels but the direction of the association varied according to the blood collection period. Our results suggest that accounting for the time of year in future research regarding vitamin status and related public health recommendations may be relevant.Electronic supplementary materialThe online version of this article (10.1186/s12877-017-0644-8) contains supplementary material, which is available to authorized users.

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“…For characterization purposes individuals were still classified according to the Institute of Medicine (IOM) criteria as being at risk of deficiency at serum 25(OH)D concentrations <12 ng/mL, at risk for inadequacy at levels ranging from 12–<20 ng/mL and having sufficient levels when 25(OH)D concentrations are ≥20 ng/mL [ 37 ]. Data concerning 25(OH)D levels in Nutrition UP 65 study were previously described [ 8 , 38 ].…”

Assessing the impact of a mushroom-derived food ingredient on vitamin D levels in healthy volunteers

“…As dietary intake of total vitamin D was maintained between groups across the intervention, the increases observed in 25(OH)D 3 , particularly in the vitamin D 2 and PL groups, are most likely explained by a rise in the UV index (UVI), registered for Cambridgeshire, UK [54] towards the end of our intervention. Cardoso et al (2017) reported that a higher UVI would impose a greater probability for endogenous production of vitamin D 3 . In their study, 25(OH)D TOTAL started to increase once UVI was ≥3 [55].…”

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“…[8][9][10][11][12][13][14], так и в других регионах мира (Англия, Португалия, Польша, Южная Корея и др.) [15][16][17]. Как правило, недостаточность витамина D (<30 нг/мл) разными авторами из разных стран, в т. ч. и РФ, регистрируется более чем у половины обследуемой популяции.…”

“…Полученные нами данные свидетельствуют, что на уровень витамина D в сыворотке крови статистически достоверно влияет время года, когда брали кровь у пациента, что, конечно, связано с солнечной инсоляцией. В Северном полушарии время года, когда у пациентов выявляют наиболее высокие концентрации кальцидиола, -лето-осень [8,10,11,15,20]. В Москве при обследовании 1041 ребенка в возрасте от 1 месяца до 18 лет (2012-2015 гг.)…”