Age as a factor affecting erythrocyte osmotic fragility in males.

Osmotic fragility and erythrocyte dimensions were measured in 40 normal males between the ages of 18 and 78 years. The principal independent variables correlating with osmotic fragility were mean cell haemoglobin concentration and the age of the donor. The age-related effect was shown to increase both the mean fragility of the cells and the variability of the fragilities of the cells within the individual blood sample. The physical basis for the change is an increase in the degree of isometric sphering of the erythrocytes at isotonicity. The change in shape does not appear sufficient to affect capillary perfusion significantly in normal subjects, but suggests that cell shape will increase the vulnerability of the elderly to abnormalities of the microvasculature.