Birth season predicts the values of red blood cell distribution width (RDW) in adulthood

Recent evidence suggests that red blood cell distribution width (RDW), a simple measure of anisocytosis, may predict the risk of adverse clinical outcomes in both the general population and in patients with severe pathologies. Since it was also shown that the birth season influences the lifetime disease risk, this study was aimed to investigate whether an association may exist between adult RDW values and birth season.

The study population consisted in healthy Caucasian blood donors aged 18 or older, undergoing routine laboratory testing before regular blood donation.

Overall, 6122 healthy blood donors were included in this study (median age 41 years; 1807 women and 4315 men). Age, sex, mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) but not hemoglobin and hematocrit were found to be independent predictors of RDW. When the study population was classified according to birth season, a significant difference was found for RDW values, but not for age, sex, hemoglobin, hematocrit, MCV and MCH. Subjects born in spring exhibited RDW values generally higher compared to those born in other seasons, reaching statistical significance when compared to those born in summer and winter. In particular, subjects born in spring had a 33% (p=0.014) higher probability of displaying increased RDW values in adulthood compared to those with summer birth.

Despite additional studies that are needed to confirm these original findings, the evidence that a significant link exists between birth season and adult anisocytosis provides a plausible explanation for the association between birth season and lifetime disease risk.