Do Harsh and Dangerous Heatwaves Accelerate "Aging"? What Happens Inside the Body? Latest Research and Practical Measures in Japan

1. "Extreme Heat Accelerates Aging"—Not a Hypothesis, but a "Reality" with Multiple Overlapping Pathways

1-1. Why We Become More Susceptible to Heat as We Age

Humans regulate body temperature through sweat and skin blood flow. This regulatory ability declines with age, making dehydration more likely, which means that the same heat can cause more damage to internal organs in the elderly. Heat leads to blood concentration (hemoconcentration) and increased viscosity, worsening circulation in the heart, brain, and kidneys, and damaging endothelial function. These changes also increase the risk of thrombosis and myocardial ischemia.BioMed CentralPMCPMC

1-2. Impact and Alert Levels in Japan

In Japan, a "Heat Stroke Alert" is issued at a WBGT (Wet Bulb Globe Temperature) of 33, and a "Special Heat Stroke Alert" at 35 (from 2024), urging the suspension of outdoor activities and seeking shelter indoors.Ministry of the Environment

Additionally, the Lancet Countdown 2024 (Japan) reported a sharp increase in the number of heatwave exposure days for those aged 65 and over, and a loss of 2.2 billion working hours in 2023 (economic loss of approximately 37.5 billion USD). It is evident that high temperatures affect not only health but also life and the economy.Lancet Countdown

2. The Chain Reaction from "Cells to Organs" that Accelerates Aging

2-1. Breakdown of Proteostasis: Weakening of HSF1/HSP

The heat shock response (HSF1→HSP induction) that counters heat stress is a lifeline responsible for protein quality control. However, it has been shown that HSF1 activity in the brain decreases with age, reducing repair and protection capabilities under heat stress. A decrease in HSP leads to increased cellular aging, while a higher amount of HSP suppresses aging—a consistent trend shown in systematic reviews.PMCPubMed

2-2. Oxidative Stress and Mitochondrial Damage

High temperatures increase reactive oxygen species (ROS), leading to mitochondrial damage and dysfunction. Oxidative stress induces apoptosis and cellular aging through DNA damage, lipid peroxidation, and protein oxidation, forming the basis for age-related diseases. Recent reviews have organized the understanding that OS and mitochondrial abnormalities are drivers of aging.PMCPMC

2-3. DNA and Telomeres: High Temperatures and "Biological Age"

In Germany's KORA cohort (F3/F4, n=5,864), daily increases in ambient temperature were associated with leukocyte telomere shortening (average -6.69% with a 0–13 day lag). Telomere shortening is a representative indicator of biological aging progression.US EPA

2-4. Vascular Endothelium and Coagulation System: Dehydration→Viscosity Increase→Microthrombosis

In extreme heat, dehydration progresses, making blood viscosity increase and endothelial function decline more likely, with coagulation system activation and immune-inflammatory responses overlapping, making microthrombosis more likely to form. In severe cases, immune thrombosis (NETs) formation in renal glomeruli has also been reported.PMCPMC

2-5. Organ-Specific Effects

• Cardiovascular: It has been shown that heart rate and cardiac workload increase during high temperatures, leading to increased cardiovascular mortality.PMCNature
  
  

• Kidneys: Heat is associated with the risk of acute kidney injury (AKI) and chronic kidney disease (CKD) in outdoor workers. An increase in future kidney disease burden is also pointed out.LancetPubMedLancet
  
  

• Brain and Cognition: High temperatures are associated with an increased risk of nighttime mortality and cognition-related mortality, and social epidemiology shows accelerated cognitive decline in high-exposure groups.ehp.niehs.nih.govJAMA NetworkPubMed
  
  

• Skin: Infrared and heat increase **MMP (collagen-degrading enzymes)** and decrease dermal collagen production—factors that worsen wrinkles and sagging over time.Wiley Online LibraryOxford Academic
  
  

3. "Night Heat" Pushes Aging Circuits: Disruption of Sleep and Circadian Rhythms

Core body temperature decreases at night to allow for deep sleep. Tropical nights hinder this cooling, leading to reduced sleep time and deep sleep. Multi-country data, including Japan, show that **"hot nights" are associated with increased mortality risk in the elderly**, and chronic sleep deprivation during high-temperature periods accelerates cognitive and metabolic deterioration.ehp.niehs.nih.govScienceDirect

4. "Medications" Can Amplify Heat Risks and Aging Stress

Diuretics, anticholinergics, some psychotropics, β-blockers, ACE inhibitors/ARBs, etc., can increase the risk of heat-related disorders by suppressing sweating, reducing skin blood flow, dulling thirst sensation, and causing electrolyte imbalances. Combinations that increase danger have also been reported. Do not stop medications on your own; consult your doctor about dosage and hydration plans during summer.Centers for Disease Control and PreventionPMC

5. Grasp the Mechanisms with a "Blueprint"

Main Pathways of Extreme Heat→Aging Acceleration (Key Points)