. 2024 Feb 8;132(2):027003. doi: 10.1289/EHP13159

Table 5.

Indices of fluid consumption and hydration status in 16 older adults at the end of randomized 8-h exposures to a range of conditions simulating those experienced indoors during hot weather and heat waves (26–36°C).

Variable	Ambient temperature ( $mean \pm SD$ )				Difference from 22°C [mean (95% CI)]^a			Linear trend ( $Δ / ° C$ $T_{ambient}$ )^a
Variable	22°C	26°C	31°C	36°C	26°C	31°C	36°C	Linear trend ( $Δ / ° C$ $T_{ambient}$ )^a
Fluid consumption (L)	0.48 (0.34)	0.54 (0.44)	0.76 (0.48)	1.22 (0.75)	0.06 ( $negative 0.17$ , 0.29) $lowercase italic p greater than 0.999$	0.28 (0.05, 0.50) $lowercase italic p equals 0.148$	0.74 (0.51, 0.96) $lowercase italic p less than 0.001$	0.05 (0.04, 0.07) $uppercase italic p less than 0.001$
Net fluid loss (% body weight)^b	$negative 0.6$ (0.8)	$negative 0.7$ (0.5)	$negative 0.5$ (0.7)	$negative 0.5$ (1.2)	$negative 0.1$ ( $negative 0.4$ , 0.3) $lowercase italic p greater than 0.999$	0.1 ( $negative 0.2$ , 0.5) $lowercase italic p greater than 0.999$	0.1 ( $negative 0.2$ , 0.5) $lowercase italic p greater than 0.999$	0.01 ( $negative 0.01$ , 0.04) $uppercase italic p greater than 0.999$
Average sweat rate ( ${g / h / m}^{2}$ )^c	20 (30)	26 (15)	31 (15)	80 (24)	7 ( $negative 6$ , 20) $lowercase italic p greater than 0.999$	22 (8, 35) $lowercase italic p equals 0.011$	60 (47, 73) $lowercase italic p less than 0.001$	4 (3, 5) $uppercase italic p less than 0.001$
Change in plasma volume (% baseline)	$negative 2.4$ (2.5)	$negative 0.5$ (3.2)	2.5 (2.5)	1.1 (4.1)	1.8 (0.2, 3.5) $lowercase italic p equals 0.214$	4.8 (3.2, 6.5) $lowercase italic p less than 0.001$	3.5 (1.8, 5.1) $lowercase italic p equals 0.001$	0.28 (0.17, 0.39) $uppercase italic p less than 0.001$

Note: Values are mean and SD or mean and 95% CI of data measured during the 8-h indoor exposure simulations ( $lowercase italic n equals 16$ ). —, no data; CI, confidence interval; SD, standard deviation.

^{^a}

Estimated marginal mean difference and linear trend derived from a linear mixed-effects model adjusted for baseline values. $p$ -Values are adjusted for multiplicity using the Holm-Bonferroni technique. All indices of body fluid status were considered a family of comparisons and adjusted simultaneously.

^{^b}

Net fluid loss was calculated as the percentage change in nude body weight from baseline to the end of exposure and was not corrected for fluid consumption or urination.

^{^c}

Average hourly sweat rate calculated from the change in body mass corrected for urination and food and fluid consumption and presented relative to body surface area.