SEASONAL VARIATION IN HbA1c AND 25(OH) VITAMIN D CONCENTRATIONS IN THE TURKISH POPULATION: COULD RAMADAN BE CHANGING EXPECTATIONS?

Abstract

Objective: In this study, the seasonal variations of HbA1c and serum 25(OH) vitamin D were investigated during different seasons in Istanbul. Materials and Methods: The alterations in HbA1c and vitamin D were evaluated concerning age and sex. The study consisted of 86,835 samples, selected from the Istanbul Faculty of Medicine Electronic Medical Records. Results: LC-MS/MS quantified 25(OH)D levels, and HbA1c were measured in HPLC. The HbA1c level in women was significantly lower than in men (p<0.001), and the HbA1c level was higher in summer compared with winter (p<0.001) and autumn (p=0.005). The 25(OH)D levels of all groups was 28.2±15.5 ng/mL with no difference between men and women. The highest vitamin-D levels were in summer, and the lowest were in winter. Conclusion: Studies have shown that in both hemispheres of the world, HbA1c levels decrease when the air is warm and increase when the weather is cold. However, contrary to expectations, we witnessed that HbA1c wa s 0.3% higher in summer than in winter in Istanbul, where the temperature change over a year is 22.5°C, the coldest month is January, and the hottest month is August. A possible explanation of our findings could stem from the occurrence of Ramadan in the summer months between 2015-2017. However, variations between HbA1c and 25(OH)D related to temperature changes during the year and age groups were detected.

Keywords

• Diabetes mellitus
• vitamin D
• seasonal variation
• HbA1c
• Ramadan

TÜRK TOPLUMUNDA HbA1c VE 25(OH)D VİTAMİNİ KONSANTRASYONLARINDAKİ MEVSİMSEL DEĞİŞİM: RAMAZAN BEKLENTİLERİ DEĞİŞTİRİYOR OLABİLİR Mİ?

Abstract

Amaç: Bu çalışmada İstanbul’da farklı mevsimlerde HbA1c ve serum 25(OH) vitamin D’nin mevsimsel değişimleri araştırılmıştır. Gereç ve Yöntem: Çalışmada kullanılan 86.835 örnek, İstanbul Tıp Fakültesi Elektronik Tıp Kayıtlarından seçilmiştir. HbA1c ve vitamin D düzeyindeki değişiklikler yaş ve cinsiyete göre değerlendirilmiştir. 25(OH)D seviyeleri LC-MS/MS, HbA1c ise HPLC yöntemleriyle ölçülmüştür. Bulgular: HbA1c düzeyi kadınlarda erkeklere göre anlamlı olarak düşük (p<0,001) ve yaz aylarında, kış (p<0,001) ve sonbahar (p=0,005) ayları ile karşılaştırıldığında daha yüksek bulunmuştur. 25(OH)D ortalaması 28,2±15,5 ng/mL olup, erkekler ve kadınlar arasında fark bulunmamıştır. En yüksek D vitamini seviyelerinin yaz aylarında, en düşük ise kış aylarında olduğu görülmüştür. Sonuç: Çalışmalar, dünyanın her iki yarım küresinde de hava ısındığında HbA1c seviyelerinin azaldığını, hava soğuk olduğunda ise arttığını göstermektedir. Ancak bir yıl içinde sıcaklık değişiminin 22,5°C olduğu, en soğuk ayın Ocak, en sıcak ayın ise Ağustos olduğu İstanbul’da HbA1c’nin beklenenin aksine yaz aylarında kış aylarına göre %0,3 daha yüksek olduğu görüldü. Bu durumun, 2015-2017 arasındaki yaz aylarında Ramazan ayının varlığından kaynaklanıyor olabileceği düşünüldü. Öte yandan HbA1c ile 25(OH)D arasında yıl ve yaş gruplarındaki sıcaklık değişimlerine bağlı farklılıklar tespit edildi

Keywords

• Diabetes mellitus
• vitamin D
• mevsimsel değişiklikler
• HbA1c
• Ramazan

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