Hypothermia

There are different types of hypothermia, which depend on how quickly the body loses heat.

• Acute or immersion hypothermia occurs when a person loses heat very rapidly, for example by falling into cold water.
• Exhaustion hypothermia occurs when a person's body is so tired it can no longer generate heat.
• Chronic hypothermia is when heat loss occurs slowly over time. This is common in elderly people living in a poorly heated house, or in people sleeping rough.

When your body gets cold, the normal response is to warm up by becoming more active, putting on more layers or moving indoors. But if exposure to the cold continues, your body's automatic defence system will try to prevent any further heat loss by:

• shivering (which keeps the major organs at normal temperature),
• restricting blood flow to the skin, and
• releasing hormones to generate heat.

After prolonged exposure to the cold, these responses are not enough to maintain body temperature, as they also drain energy.

When the body's energy is exhausted, it slowly starts to shut down. Shivering stops and your heartbeat begins to slow. This life-threatening stage can develop very quickly, so it is vital that hypothermia is treated as a medical emergency.

Each year in the UK, hypothermia is the main contributing factor to the deaths of more than 400 people over the age of 65.

Elderly people and those who are ill and unable to move around easily are especially vulnerable to hypothermia. This can be due to poorly heated accommodation, not eating enough or not being active enough to generate energy.