# Effects of seasonal temperature variability on glucose levels in acute ischemic stroke patients

## TL;DR

This study found that glucose levels in stroke patients vary by season, with higher levels and worse outcomes in winter.

## Contribution

The study reveals seasonal glucose fluctuations in stroke patients and their impact on stroke severity.

## Key findings

- Winter had higher fasting glucose levels in diabetic stroke patients compared to summer.
- HbA1c levels varied seasonally, with the largest differences in spring and summer compared to autumn.
- Winter admissions correlated with greater stroke severity, linked to lower temperatures and higher glucose levels.

## Abstract

This study investigated seasonal temperature variability in glycemic parameters and their clinical correlates in 8730 acute ischemic stroke (AIS) patients admitted from 2013 to 2022. Patients were grouped by season of onset, with collection of demographic characteristics, laboratory results, admission NIHSS scores and meteorological data. After confounder adjustment, generalized additive model(GAM) was used to evaluate the correlation between ambient temperature, glycemic parameters and NIHSS scores, with interactions examined via season stratification. In patients with diabetes, fasting plasma glucose (FPG) levels in winter increased by 1.22 mmol/l (95% CI:1.14,1.29 mmol/l, P < 0.01) versus summer. General linear model analysis revealed lower FPG levels in summer (β = -0.083, 95% CI: -0.726, -0.062; P < 0.05) and autumn (β = -0.125, 95% CI: -0.590, -0.073; P < 0.05) versus winter. HbA1c demonstrated similar seasonal variation, particularly when values exceeding 7.0%, with spring-autumn differences reaching 0.81 units (95% CI: 0.61, 1.02; P < 0.05). HbA1c variations were most pronounced in spring (β = 0.201, 95% CI: 0.099, 0.557; P < 0.001) and summer (β = 0.107, 95% CI: 0.096, 0.449; P < 0.05) versus autumn. Winter admissions correlated with greater stroke severity, supported by 1 ◦C temperature decrease was associated with 2.5 (95% CI: -4.5, -0.5;P < 0.01) NIHSS scores increase. Of note, each 0.1 mmol/L increment in FPG corresponding to a 0.8 rise in NIHSS scores (95% CI: 0.5, 1.1, P < 0.01), while HbA1c showed no association. Our findings demonstrated AIS patients showed seasonal glucose fluctuations, with the highest hyperglycemia and severity in winter. The robust association between FPG and outcomes highlighted the need for seasonally-adjusted glucose management in high-risk populations.

The online version contains supplementary material available at 10.1007/s00484-025-03103-2.