Extreme temperatures attract attention, but cold causes most excess deaths
This large observational study found that cold causes more excess deaths than very high temperatures. Problems caused by heat occur within a few days while the effect of cold lasts three or four weeks.
The effects of cold can last for weeks
Although extreme temperatures receive the most attention the greatest mortality is from exposure to moderate cold. This has been associated with cardiovascular stress factors such as blood pressure changes, vasoconstriction and changes in plasma fibrinogen and blood viscosity as well as inflammatory responses.
Cold also induces bronchoconstriction and suppresses mucociliary defences and other immunological reactions resulting in increased risk of respiratory infections.