However, hypothermia is one of the most deadly cold-induced conditions and, if not caught and treated early on, can lead to a rapid decline in the body's ability to function normally. Hypothermia occurs when the body's core temperature is lowered due to exposure to cold. It can occur even at mild temperatures if exposure is prolonged. The body's natural defences against the cold consist of restricting the flow of blood to the skin so as to prevent heat loss, along with shivering and releasing hormones to generate heat. These measures are limited and are usually inadequate to maintain body temperature in cold environments.
Symptoms take effect in three stages.
The elderly and babies under one year old are most at risk among people with no other complaints. However, people who already have something wrong with them are also at a higher risk, as they may not be aware of how severely they are exposing themselves to the cold. Due to their sleeping arrangements, the homeless are also particularly at risk. People who expose themselves to extreme weather conditions, such as mountain climbers, are at risk, but will usually travel prepared for emergencies. They should also have some understanding of how to recognise and treat hypothermia before they set off.