John Appleby (Data briefing, 4 June) is misleadingly dismissive of the substantial body of evidence suggesting a causal relationship between income inequality, poor health and raised mortality.

While he barely acknowledges the increasing international empirical evidence supporting this relationship (which was chiefly propounded by Richard Wilkinson, and is summarised in his book, Unhealthy Societies), Mr Appleby makes great play of technical criticisms by fellow economist Hugh Gravelle.

Wilkinson has since refuted these in the British Medical Journal, describing them as 'neither new nor true'.

Alex Scott-Samuel

EQUAL (equity in health research and development unit)

Department of public health

Liverpool University

Whelan building

Quadrangle

Liverpool