The Impact of Sleep on Haematological Parameters in Firefighters

Abstract

Sleep is a vital process that impacts biological functions such as cell renewal, bone regeneration, and immune system support. Disrupted sleep can interrupt erythropoiesis, leading to fewer red blood cells, reduced haemoglobin concentration, and decreased haematocrit levels, potentially contributing to haematological disorders. This is particularly concerning for shift workers for example firefighters. While previous studies have explored sleep's adverse effects on various professions, research specific to firefighters is limited. This study investigates the relationship between sleep quality and haematological parameters among firefighters in Northeast Portugal. From a sample of 201 firefighters, variations in red blood cells, haemoglobin, and haematocrit values were linked to sleep quality. The study utilised non-parametric tests (Wilcoxon-Mann-Whitney, Spearman's correlation) to explore the connection between sleep quality and haematological profile. The impact of covariates on haematological parameters was assessed using non-parametric ANCOVA (Quade's). A multiple regression analysis was employed to further understand how sleep quality and various confounding variables impact haematological levels. Findings suggest a negative link between sleep quality and haematological levels, meaning that as sleep quality deteriorates, there is a tendency for haematological levels to decrease, as indicated by Spearman's correlation (rRBC = -0.157, pRBC = 0.026; rHb = -0.158, pHb = 0.025; rHCT = -0.175, pHCT = 0.013). As observed in scientific literature, the correlation found suggests a possible inhibition of erythropoiesis, the process responsible for red blood cell production. Despite firefighters presenting a haematological profile within the reference range (RBC: 5.1 × 10⁶/mm³ (SD ± 0.4), Hb: 15.6 g/dL (SD ± 1.3), 47% (SD ± 1.0), there is already an observable trend towards lower levels. The analysis of co-variables did not reveal a significant impact of sleep quality on haematological levels. In conclusion, this study underscores the importance of sleep quality in determining haematological parameters among firefighters. Future research should investigate the underlying mechanisms and long-term implications of poor sleep quality on firefighter health. Exploring interventions to enhance sleep quality is vital for evidence-based strategies promoting firefighter well-being.

Keywords: PSQI; circadian rhythms; haematocrit; haemoglobin.

Figure 1

Box plot of haematological values ((a)—RBC, (b)—Hb, and (c)—HCT) of firefighters classified as having bad sleep quality and Good Sleep Quality. Horizontal lines indicate the median, boxes indicate the interquartile range, whiskers extend to upper adjacent values and lower adjacent values, and dots represent outliers. Note: The heamatological reference interval is indicated in the text.

Figure 2

Scatterplot with regression lines representing the relationship between haematology parameters, PSQI Sleep Quality Total Score, and sex. Haematologial values in the Y-axis and PSQI sleep total scores, ranging from 0 to 21 in the X-axis. Males are in the star and solid red regression lines; females are in open circles and dashed blue regression lines.

Figure 3

Linear regression lines represent the relationship between Haematology parameters, PSQI Sleep Total Scores, and BMI. Haematologial values in the Y-axis and PSQI sleep total scores, ranging from 0 to 21 in the X-axis. Excess weight is represented by a star and a solid red regression line, and regular weight is represented by open circles and a dashed blue regression line.

Figure 4

Linear regression lines represent the relationship between Haematology parameters, PSQI sleep total scores and coffee intake. Haematologial values in the Y-axis and PSQI sleep total scores, ranging from 0 to 21 in the X-axis. Nil coffee intake is represented by a star and a solid red regression line, and coffee consumption is represented by open circles and a dashed blue regression line.