Associations between hydration status, body composition, sociodemographic and lifestyle factors in the general population: a cross-sectional study

Abstract

Background: Whole-body hydration status is associated with several health outcomes, such as dehydration, edema and hypertension, but little is known about the nonclinical determinants. Therefore, we studied the associations of sex, age, body composition, nutrition, and physical activity on several body hydration measures.

Methods: We assessed sociodemographic variables, dietary habits, and physical activity by questionnaire and body composition by bioelectric impedance analysis (BIA). We compared determinants between the sexes and calculated associations between determinants and BIVA hydration measures by multivariable linear regressions.

Results: A total of 242 adults from the general population (age 18-94, 47% women) were included. Women were younger, smaller, lighter, and had a smaller BMI (kg/m²) than men (p < 0.05). Women had less muscle mass, less visceral fat mass and less extracellular and intracellular water than men (p < 0.001). Women showed less intracellular water per extracellular water than men, while men showed higher phase angle values than women (both p < 0.001). Men had a stronger association of hydration measures with physical activity than women. Both sexes showed a decrease in hydration measures with age.

Conclusions: Sex, age, body composition, and physical activity influence body hydration. There seem to be differences in body water regulation between the sexes. Especially interesting are factors susceptible to preventive measures such as physical activity.

Keywords: BIA; Body hydration; Overweight; Physical activity; Sex differences.

Fig. 1

Boxplots of extracellular water per fat free mass (ICW/FFM), per age quartile in women and men. 1 = youngest quartile, 4 = oldest quartile

Fig. 2

Boxplots of phase angle per age quartile in women and men. 1 = youngest quartile, 4 = oldest quartile

Fig. 3

The 95% confidence ellipses for the mean impedance vectors of men (red) in comparison with women (black). R/H: height-adjusted resistance; Xc/H: height-adjusted reactance. The p-value is from the two-samples Hotelling’s T²-Test

Fig. 4

Scatterplot of individuals in four age quartiles of men (left) and women (right), plotted on the 50%, 75%, and 95% tolerance ellipses of the corresponding reference populations. Group 1 (yellow): first quartile (youngest); group 2 (red): second quartile; group 3 (green): third quartile; group 4 (blue): fourth quartile (oldest). Z(R): Z-transformed resistance; Z(Xc): Z-transformed reactance