# Seasonal Variations in Estimated Whole Blood Viscosity Associated with HbA1c: Evidence from Retrospective Pathology Review for Diabetes Management

## TL;DR

Blood viscosity increases in colder seasons, which may affect diabetes management and cardiovascular risk.

## Contribution

This study identifies seasonal variations in estimated whole blood viscosity and its biomarkers over a 10-year period.

## Key findings

- Whole blood viscosity, haematocrit, and serum total protein levels peak in winter (p < 0.001).
- Seasonal variation in glycated haemoglobin levels was not statistically significant.
- Seasonal fluctuations in blood viscosity can inform diabetes risk management strategies.

## Abstract

Elevation in the level of whole blood viscosity (WBV) is a known contributor to cardiovascular risk. Moreover, cardiovascular diseases are associated with seasonal variation and the potential impact of seasonal changes on blood viscosity, and associated biomolecules pose substantial cardiovascular risk and are therefore a subject of interest. To evaluate the effect of seasonal changes on whole blood viscosity, glycated haemoglobin and associated biomolecules, namely haematocrit and serum total protein, and their implications on management of diabetic cardiovascular risk are explored. This was a clinical laboratory retrospective observational study involving 10-year pathology data (1999–2008) which estimated whole blood viscosity (eWBV) and the associated biomolecules, namely haematocrit and serum total protein. Comparisons were made between seasonal changes and glycated haemoglobin, whole blood viscosity, haematocrit, and serum total protein levels. Whole blood viscosity, haematocrit, and serum total protein levels increased with colder seasons (p < 0.001), peaking in the winter. However, the seasonal variation in the level of glycated haemoglobin did not achieve statistical significance. Blood viscosity fluctuates between seasons, with peaks occurring in the winter season. This fluctuation will assist in adjusting monitoring and treatment strategies of diabetic risks seasonally. In addition, recognition of seasonal variations will help in precise risk assessment of timely interventions to mitigate the risk of cardiovascular events in diabetes management.