Are central heating and artificial lighting making us ill?

Our bodies naturally adapt to cold, dark winter conditions. Scientists think the rise of warm houses and bright lights has baffled our immune systems

It's time to turn down the heating and switch off the lights - all this cosiness is making us ill. At least that sounds like the advice from new research which suggests the "endless summer" we have created in our homes could be playing havoc with our health, and even causing early deaths.

Scientists now believe that up to a quarter of our genes are seasonal - and that those controlling our immunity become more active in cold months than during summer days, helping us to fight off diseases such as flu.