Abstract
BACKGROUND: The Circassian community in Israel represents a unique, endogamous population residing in two villages in the northern region of Israel: Kfar Kama (209 meters above sea level [m.a.s.l.]) and Rihaniya (674 m.a.s.l.). OBJECTIVES: This study sought to investigate whether the small difference in altitude between these two locations (465 m) affects red blood cell (RBC) and hemoglobin (Hb) parameters in the residents. METHODS: We examined the data from 2,517 blood samples collected from adult Israeli Circassians over 2.5 years (January 2020-June 2022). To ensure independent observations, analysis was limited to each participant's most recent complete blood count (CBC). Subjects were stratified by sex, age, anemia status, and residential location. RESULTS: Our analysis revealed that a difference of about 465 meters in residential altitude significantly elevated Hb, RBC count, and hematocrit (HCT) levels in non-anemic male and female cohorts. This elevation was accompanied by a small but significant decrease in mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH). Furthermore, we found that the effect of altitude on most RBC characteristics differed in anemic individuals of both sexes, although their RBC count still increased. CONCLUSIONS: Even minor differences in residential altitude can significantly influence Hb and RBC parameters. This observation appears only in non-anemic individuals, probably reflecting physiological altitude Hb adaptation mechanisms. While further research is needed to fully elucidate the underlying mechanisms, our findings provide new data on the physiological impact of altitude on human health, particularly at low altitudes.