Prominent seasonality of 25(OH)D vitamin deficiency in Latvia: Age and gender-related variations and testing regimen

Sergey Nikulshin,Stella Lapina,Anda Krisane,Jana Osite,Dace Gardovska,Iveta Dzivite-Krisane,L Vilka,J Vike

doi:10.1051/shsconf/202213102004

Abstract

Seasonality of 25(OH)D deficiency rate is a factor of major clinical and social impact and should be considered when planning for appropriate testing and tailored correction. We present retrospective cross-sectional analysis of over a million 25(OH)D tests performed in two leading Latvian laboratories – Central Laboratory and E.Gulbja Laboratory. Both series of tests demonstrated prominent seasonal variability of 25(OH)D deficiency rate (<20 ng/ml) and critical deficiency rate (<12 ng/ml): the lowest percentage of deficient tests was in August, while a significant peak was found in March-April. This trend was present at all ages and in both genders, variations were pronounced even for a high-latitude country and more prominent for critical deficiency, in younger age groups and in males. Analysis of testing regimens of both laboratories revealed that schedule was not optimal, period of higher testing intensity being far removed from the 25(OH)D deficiency peak.

Highlights

Considerable seasonal variations of vitamin D and its active metabolite 25(OH)D have been described in 1970-ies, with insolation level proven as the main contributing factor, more important than diet or race [1, 2]
There were well-defined negative peaks in August for both overall deficiency rate and critical deficiency, and the highest rates were found in March (CL) or in April (EGL), the positive peaks being less steep
Seasonality was striking in case of critical deficiency rate: almost nonexistent in August in all age groups except the elderly, it increased 20-fold and more in children and young adults

Summary

Introduction

Considerable seasonal variations of vitamin D and its active metabolite 25(OH)D have been described in 1970-ies, with insolation level proven as the main contributing factor, more important than diet or race [1, 2]. The phenomenon was later confirmed by extensive crosssectional and longitudinal analysis [3,4,5,6,7,8] These variations are more pronounced in countries with seasonal climate and in high-latitude regions, where most studies note minimal level of25(OH)D and maximal deficiency rate in winter or early spring, and maximal level with matching drop of deficiency rate in late summer [5-7, 9, 10, 11,]. It should be considered by any national testing and correction program, in higher-latitude countries

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Conclusion