How do low temperatures predispose to upper respiratory tract infections (URTI)?

From the Guidelines

Cold temperatures predispose individuals to upper respiratory infections by compromising the immune system, drying out the protective mucus lining, and creating an environment where viruses can survive and replicate more efficiently. The most recent and highest quality study, 1, published in 2023, highlights the impact of housing quality on inequalities in health and well-being, particularly in relation to temperature and respiratory disease. Key findings from this study and others suggest that:

• Low indoor temperatures can exacerbate cardiovascular and respiratory conditions, leading to increased morbidity and mortality, especially among vulnerable populations such as the young and older people 1.
• Inadequately heated houses are more likely to be damp, leading to mold growth, which can cause respiratory difficulties independent of temperature 1.
• Improving thermal efficiency in older housing through initiatives like insulation and heating programs can have significant health benefits, including reduced hospitalizations and improved self-reported health 1.
• The use of heating vouchers or payments, such as the Winter Energy Payment in New Zealand, can help reduce fuel poverty and improve health outcomes for vulnerable households 1. Some of the key physiological mechanisms by which cold temperatures increase the risk of upper respiratory infections include:
• Constriction of blood vessels in the nasal passages, reducing blood flow and limiting the delivery of immune cells 1.
• Drying out of the protective mucus lining of the nose and throat, compromising this important barrier against pathogens.
• Creation of crowded conditions where viruses can spread more easily from person to person through respiratory droplets.
• Improved survival and replication of certain viruses, such as rhinoviruses and influenza viruses, in cooler temperatures 1. To reduce the risk of upper respiratory infections during cold weather, it is essential to:
• Maintain proper hydration
• Use humidifiers indoors
• Wash hands frequently
• Ensure adequate vitamin D levels to support immune function.

From the Research

Mechanisms of Cold Temperature and Upper Respiratory Infections

• Cold temperature has been associated with an increased risk of upper respiratory tract infections (URTI) due to several mechanisms, including vasoconstriction in the respiratory tract mucosa and suppression of immune responses 2.
• Exposure to cold air, cooling of the body surface, and cold stress induced by lowering the core body temperature can cause pathophysiological responses that increase susceptibility to infections 2.
• However, not all studies agree on the relationship between cold exposure and immune function, with some suggesting that cold exposure does not depress immune function 3.

Risk Factors and Associations

• Cold temperature and low humidity have been shown to be associated with an increased occurrence of respiratory tract infections, including URTI and lower respiratory tract infections (LRTI) 4.
• A decrease in temperature and humidity has been found to precede the onset of URTI, LRTI, and common cold, suggesting a potential trigger for these infections 4.
• The mechanisms behind cold air-provoked respiratory symptoms vary depending on individual susceptibility and ventilation level during cold exposure, and can include short-term and long-term responses to cold air 5.

Management and Prevention

• Early intervention has been shown to be effective in reducing the severity and transmission of URTI, and can include the use of mucoadhesive gel nasal sprays to create a barrier against virus particles 6.
• Understanding the mechanisms of cold temperature and URTI is essential for successful management and prevention of these infections, and can inform public health strategies to reduce morbidity and mortality during winter months 2, 4.