# Whole Blood Viscosity and Its Associations with Age, Hematologic Indices, and Serum Biochemical Variables in Clinically Healthy Beagle Dogs and Korean Shorthair Cats

## TL;DR

This study found that blood viscosity in healthy dogs and cats does not change with age and is mainly influenced by red blood cell levels and other blood components.

## Contribution

The study is the first to show that blood viscosity in healthy companion animals is not age-dependent but is linked to hematologic and biochemical variables.

## Key findings

- Whole blood viscosity did not vary with age in healthy Beagle dogs and Korean Shorthair cats.
- WBV was strongly associated with red blood cell count, hematocrit, and hemoglobin in both species.
- In dogs, serum proteins and cholesterol also contributed to variations in whole blood viscosity.

## Abstract

Whole blood viscosity (WBV) is a key determinant of blood flow, and age-related changes have been reported in humans. To determine whether similar patterns occur in companion animals, we measured WBV across multiple shear rates in healthy Beagle dogs and Korean Shorthair cats. We found that WBV did not vary with chronological age in either species, indicating that physiological aging alone did not alter blood viscosity in healthy animals. Instead, WBV was primarily associated with erythrocyte-related variables, with serum biochemical components providing an additional contribution in dogs. These findings suggest that WBV remains stable throughout adulthood in healthy dogs and cats, providing a useful context for interpreting viscosity measurements in veterinary practice.

This study investigated whether Whole blood viscosity (WBV) varies with age in clinically healthy Beagle dogs and Korean Shorthair cats and examined the hematologic and biochemical variables associated with WBV. WBV was measured across multiple shear rates using a scanning capillary viscometry; complete blood count (CBC) and serum chemistry profiles were also evaluated. Both species demonstrated characteristic shear-thinning behavior. WBV showed a strong association with red blood cell count (RBC), hematocrit (HCT), and hemoglobin (Hb) in both species, with additional association with serum proteins and cholesterol in dogs. No significant relationship between WBV and age was identified at any shear rate, and principal component analysis (PCA) revealed no age-related clustering in the viscosity profiles. These findings indicated that WBV does not exhibit meaningful age-dependent trends in healthy companion animals. This suggests that, in a clinical setting, deviations in normal WBV are more likely to influence underlying physiological or pathological factors than normal aging.