Seasonal Variability in Metabolic Profiles Among Individuals With Type 2 Diabetes: A One-Year Retrospective Analysis

Year 2026, Volume: 21 Issue: 1, 1 - 8, 28.03.2026

Vehbi Şirikçi

https://doi.org/10.17517/ksutfd.1844848

https://izlik.org/JA62GZ88PZ

Abstract

Objective: This study aimed to evaluate the seasonal variation in HbA1c levels among individuals with type 2 diabetes (T2D) and to examine the relationship between these fluctuations and lipid parameters. Materials and Methods: In this retrospective cross-sectional study, 823 adults with T2D who presented to an internal medicine outpatient clinic during 2024 were included. Between-season comparisons were performed using the Kruskal–Wallis test for non-normally distributed variables and one-way ANOVA for normally distributed variables. To determine whether the seasonal effect on HbA1c was independent of metabolic parameters, multivariable ANCOVA models were constructed. Results: HbA1c levels varied significantly across seasons (Kruskal–Wallis p < 0.05). The highest adjusted mean HbA1c occurred in winter (8.75%), whereas the lowest values were observed in summer (8.20%); the summer–winter contrast remained significant (p = 0.035). In the multivariable ANCOVA model, triglycerides were positively associated with HbA1c (β = 0.002; 95% CI: 0.001–0.003; p < 0.001), whereas HDL cholesterol showed an inverse association (β = –0.019; 95% CI: –0.031 to –0.007; p = 0.002). Notably, seasonal differences remained independently significant after adjusting for lipid parameters (overall seasonal effect p = 0.021). Conclusion: HbA1c levels showed a distinct seasonal pattern, improving during summer and worsening during winter in individuals with T2D. Independent associations of HbA1c with triglycerides and HDL cholesterol suggest that seasonal glycemic variation occurs in interplay with underlying metabolic features. These findings underscore the clinical relevance of incorporating seasonal factors into diabetes management strategies.

Keywords

Type 2 diabetes , Hba1c , Seasonal variation , Lipid metabolism , Triglycerides , HDL-cholesterol

Ethical Statement

Ethical approval for this study was obtained from the Kahramanmaraş Sütçü İmam University Medical Research Ethics Committee (Date: 08.12.2025, Decision No: 2025/35-02).

Supporting Institution

None

Project Number

361

Thanks

Not applicable.

Tip 2 Diyabetli Hastalarda Mevsimsel Metabolik Profil Değişkenliği: Bir Yıllık Retrospektif Analiz

https://izlik.org/JA62GZ88PZ

Abstract

Amaç: Bu çalışma, Tip 2 diyabetli (T2D) bireylerde HbA1c düzeylerinin mevsimsel değişimini ve bu varyasyonun lipid profili ile ilişkisini tanımlamayı amaçlamaktadır. Gereç ve Yöntemler: Bu retrospektif kesitsel çalışmaya, 2024 yılı boyunca bir şehir hastanesinin iç hastalıkları polikliniğine başvuran 823 T2D tanılı birey dahil edilmiştir. Mevsimsel farklılıklar; normal dağılım göstermeyen değişkenler için Kruskal–Wallis testi, normal dağılım gösteren değişkenler için ise tek yönlü ANOVA ile değerlendirilmiştir. Mevsimsel etkinin trigliserid ve HDL-kolesterol gibi metabolik kovaryatlardan bağımsızlığını test etmek amacıyla çok değişkenli ANCOVA modelleri kullanılmıştır. Bulgular: HbA1c düzeyleri mevsimler arasında anlamlı şekilde farklılık göstermiştir (Kruskal-Wallis p<0.05). Düzeltilmiş ortalama HbA1c değerleri kış mevsiminde en yüksek (%8.75), yaz mevsiminde ise en düşük düzeyde bulunmuştur (%8.20); yaz–kış karşılaştırması anlamlıdır (p = 0.035). Çok değişkenli ANCOVA analizinde trigliserid düzeyleri HbA1c ile pozitif yönde (β = 0.002; %95 GA: 0.001–0.003, p < 0.001), HDL-kolesterol ise negatif yönde ilişkili bulunmuştur (β = -0.019, %95 GA: -0.031 ile -0.007, p = 0.002). Lipid parametrelerine göre düzeltme yapıldığında dahi mevsimsel etkinin bağımsız olarak anlamlılığını koruduğu görülmüştür (genel mevsim etkisi: p = 0.021). Sonuç: T2D tanılı bireylerde HbA1c düzeyleri belirgin mevsimsel değişim göstermekte; yaz aylarında iyileşmekte, kış aylarında ise belirgin bir bozulma izlenmektedir. HbA1c ile trigliserid ve HDL-kolesterol arasındaki bağımsız ilişkiler, mevsimsel glisemik dalgalanmaların metabolik belirteçlerle etkileşim içinde geliştiğini düşündürmektedir. Bu bulgular, diyabet yönetiminde mevsimsel dinamiklerin sistematik olarak dikkate alınmasının klinik açıdan önemli olabileceğini göstermektedir.

Keywords

Tip 2 diyabet , Hba1c , Mevsimsel varyasyon , Lipid metabolizması , Trigliserit , HDL-kolestrol

Ethical Statement

Bu çalışma için Kahramanmaraş Sütçü İmam Üniversitesi Tıbbi Araştırmalar Etik Kurulu'ndan 08.12.2025 tarih ve 2025/35-02 sayılı karar ile etik onay alınmıştır.

Supporting Institution

Yoktur

Project Number

361

Thanks

Yoktur

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