The Association Between Outdoor Temperature During the Past Weeks and Current Fluid Homeostasis.

Area of Science:

• Environmental Health
• Human Physiology
• Biometeorology

Background:

• Persistent adverse health effects from cool weather compared to hot weather remain unexplained.
• Fluid homeostasis is investigated as a potential link between past temperatures and health outcomes.

Purpose of the Study:

• To investigate the association between past outdoor temperatures and current fluid homeostasis.

Main Methods:

• Studied 29,755 participants across five Swedish cohorts over three decades.
• Assessed fluid homeostasis via plasma copeptin, urine osmolality, and total water intake.
• Utilized distributed non-linear lag models to link fluid homeostasis indicators with past temperatures (21 days).

Main Results:

• Past cool temperatures showed non-linear associations with elevated plasma copeptin and urine osmolality.
• A 21-day period at 0°C correlated with a 14.9% increase in copeptin compared to 14.3°C.
• Warm temperatures had shorter-duration effects on copeptin, linked to elevated levels within 24 hours.

Conclusions:

• Altered fluid homeostasis due to cool weather may explain delayed adverse health effects.
• Moderately increasing water intake could potentially mitigate adverse health impacts of cool temperatures.