# Physiological responses to mask-associated CO2 exposure: a narrative review of acid–base balance, aging, and amyloidogenic stress

## TL;DR

This review explores how mask use during the pandemic may affect older adults' acid-base balance and increase amyloid formation risks due to age-related physiological decline.

## Contribution

The paper introduces a novel synthesis linking mask-associated CO2 exposure, aging physiology, and amyloidogenic stress pathways.

## Key findings

- Aging reduces physiological resilience to CO2-induced pH shifts, increasing amyloidogenic risk.
- Chronic low-grade hypercapnia may magnify biological impacts in older adults due to impaired buffering.
- Age-related comorbidities further predispose to acidosis and amyloid formation.

## Abstract

During the COVID-19 pandemic, prolonged mask use exposed billions of people to repeatedly elevated inhaled CO2 levels for extended periods. While these exposures typically produce only small pH shifts in healthy adults, older individuals exhibit age-related declines in respiratory, renal, metabolic, and proteostatic resilience that reduce their ability to buffer such disturbances. Because even mild acidosis can influence protein folding and accelerate amyloid formation under conditions of impaired homeostasis, aging populations may be disproportionately susceptible to downstream effects of chronic low-grade CO2 exposure.

This narrative review synthesizes data on age-related changes in ventilation, acid–base regulation, metabolic buffering, and proteostasis, integrating these with biochemical pathways of pH-dependent amyloidogenesis. Evidence from mask-related CO2 exposure studies, protein-misfolding research, and gerontological physiology was analyzed to evaluate whether age-specific vulnerability could plausibly modulate amyloidogenic risk.

Across multiple studies, mask wearing increases inhaled CO2 concentrations and produces small but measurable reductions in blood pH in some conditions. Although these changes remain within normal physiological range in healthy adults, aging is associated with impaired ventilatory responsiveness to hypercapnia, diminished renal compensation, reduced muscle-based buffering due to sarcopenia, and mitochondrial and proteostatic decline. These changes lower physiological reserve and may magnify the biological impact of minor pH fluctuations. Experimental literature consistently demonstrates that acidity accelerates amyloid formation in proteins relevant to aging disorders—including Aβ, α-synuclein, IAPP, and β2-microglobulin—while older adults also accumulate comorbidities (chronic kidney disease, diabetes, neurodegeneration) that themselves predispose to acidosis and amyloidogenic stress.

Although mask-associated CO2 elevations appear insufficient to induce amyloid formation in isolation, the combination of age-related physiological decline, chronic inflammation, impaired proteostasis, and reduced buffering capacity may heighten vulnerability in older adults. Given global demographic aging, further age-stratified research is needed to clarify long-term implications of repeated low-grade hypercapnia, refine diagnostic approaches for early detection of proteostatic stress, and develop prevention strategies tailored to aging physiology.