Letter: Wide-awake gene

Sir: As someone who is usually up by six o'clock in the morning, but who has difficulty staying awake until nine in the evening in front of the telly, I was interested to read that a "defective gene" may be the cause of my habits (report, 31 August).

Why should it be my version of the gene which is considered faulty? By getting up in the morning and taking the dogs for a walk, I warm myself up, thus saving the financial and environmental costs of heating, especially if I am tucked up by the time it cools down again at night. I also save on lighting, because for a large part of the year natural light is available in the mornings but not in the evenings.

I suggest that those of us who rejoice in the dawn chorus possess the normal form of the gene, and it is the clubbers who are defective.