Tiroid disfonksiyonunun alan spesifik bilişsel performans üzerine etkisi: kesitsel bir çalışma

Abstract

Amaç: Tiroid disfonksiyonunun bilişsel işlevler üzerindeki etkileri bilinmekle birlikte, alana özgü ilişkileri tam olarak aydınlatılamamıştır. Bu çalışma, yaşlı bireylerde tiroid fonksiyon durumu ile spesifik bilişsel alanlardaki performans arasındaki ilişkiyi incelemeyi amaçlamaktadır. Gereç ve Yöntemler: Çalışmaya, önceden tiroid hastalığı bulunmayan 50-80 yaş aralığındaki 167 birey (32 kontrol, 48 hafif bilişsel bozukluk, 86 Alzheimer hastası) dahil edilmiştir. Katılımcıların Mini-Mental Durum Değerlendirmesi (MMSE; yönelim, bellek, dikkat/hesaplama, geri çağırma ve dil) ve Klinik Demans Derecelendirmesi (CDR) ile kapsamlı bilişsel değerlendirmeleri yapılmıştır. Tiroid fonksiyonları TSH düzeylerine göre sınıflandırılmıştır: düşük (<0.55 μIU/mL), normal (0.55-4.78) ve yüksek (>4.78). İstatistiksel analizlerde Spearman korelasyon, Mann-Whitney U testleri ve sınıf dengesizliğini düzeltmek için SMOTE yöntemiyle çok değişkenli lojistik regresyon modelleri kullanılmıştır. Bulgular: Düşük TSH düzeyleri, bozulmuş geri çağırma performansı ile anlamlı şekilde ilişkili bulunmuştur (OR 0.17, %95 GA 0.06-0.46, p=0.001). Yüksek TSH düzeyleri ise yönelim ve dikkat/hesaplama alanlarında bozulma ile ilişkilendirilmiştir (p<0.001). CDR skorları ile düşük TSH arasında belirgin bir ters ilişki saptanmış olup (OR 0.036, %95 GA 0.006-0.199), demans şiddeti arttıkça düşük TSH olasılığının 27.8 kat azaldığı hesaplanmıştır. Toplam MMSE skorları ve diğer bilişsel alanlarda anlamlı bir ilişki gözlenmemiştir. Sonuç: Tiroid disfonksiyonunun bilişsel işlevler üzerindeki etkileri global değil, alana özgüdür. Hipotiroidi ve hipertiroidinin farklı bilişsel alanlarda ayrışan etkileri olduğu ve tiroid fonksiyonu ile bilişsel performans arasında karmaşık (muhtemelen U-şeklinde) bir ilişki bulunduğu görülmüştür. Bu bulgular, tiroid bozukluklarında alana özgü bilişsel değerlendirmenin önemini vurgulamakta olup, gelecekte longitudinal çalışmalarla desteklenmesi gerekmektedir.

Keywords

• Tiroid disfonksiyonu
• Bilişsel bozukluk
• kognitif alanlar
• minimental test
• demans

The impact of thyroid dysfunction on domain-specific cognitive performance: a cross-sectional study

Abstract

Aims: While thyroid dysfunction has been implicated in cognitive impairment, its domain-specific effects remain unclear. This study investigates the relationship between thyroid status and performance across distinct cognitive domains in older adults. Methods: We analyzed 166 participants (32 controls, 48 mild cognitive impairment, 86 Alzheimer's disease) aged 50-80 years without pre-existing thyroid conditions. Participants underwent comprehensive assessment including Mini-Mental State Exam (MMSE) and Clinical Dementia Rating (CDR). Thyroid status was classified by TSH levels: low (<0.55 μIU/ml), normal (0.554.78 μIU/ml), and high (>4.78 μIU/ml). Data normality was evaluated using the Shapiro-Wilk test, and non-parametric methods were applied due to non-normal distributions. Spearman’s correlation and Kruskal-Wallis tests were used for bivariate analyses. Chi-square tests assessed associations between thyroid status and categorical variables. A multinomial logistic regression model was employed to identify predictors of thyroid status, with the low TSH group as the reference category. To address class imbalance, the SMOTE technique was applied, and multicollinearity was examined using the variance inflation factor (VIF). Results: Among the MMSE subdomains, recall, orientation, and attention and calculation were significantly associated with thyroid status. Recall was a strong predictor for both normal and high TSH levels. Orientation scores positively predicted normal TSH and negatively predicted high TSH. Attention and calculation was significantly associated only with normal TSH. Additionally, higher CDR scores were significantly linked to high TSH status. Conclusion: These findings suggest that rather than evaluating global cognition, domain-specific cognitive assessment may provide more meaningful insights into the cognitive effects of thyroid dysfunction.

Keywords

• Thyroid dysfunction
• cognitive domains
• Mini-Mental State Exam
• dementia
• TSH
• cognitive impairment

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