‘The Child is Father of the Man’, wrote British poet William Wordsworth (1807), reflecting upon the consistency of an individual's emotional responses through the long human lifespan. Soon afterwards, Mendelian and Darwinian genetics and the still controversial concept of early life programming indicated plausible biological bases for Wordsworth's artistic muse. Now, nearly two centuries later, many readily accept that part of our individual emotional compass is constrained by events affecting the development of the brain before birth, effects that persist for life, defining parameters upon which nurture and the adult environment exert their modifying effects. For genetics, the effects of classically inherited genes and chromosomal variation confirm the fundamental nature of inheritance of traits. Here we address the role of a specific aspect of the early life environment upon the lifelong characteristics of an individual, a much more recent addition to understanding of ‘ease or disease’ through our span.
Epidemiology and the concept of ‘programming’
To begin, in appropriate recent historical sequence, with human epidemiology. Numerous studies, initially in the UK and then encompassing much of the world, have demonstrated an association between lower birth weight and the subsequent development of the common cardiovascular and metabolic disorders of adult life, namely hypertension, insulin resistance, type 2 diabetes and cardiovascular disease deaths (Barker, 1991; Barker et al., 1993a, b; Fall et al., 1995; Yajnik et al., 1995; Curhan et al., 1996a, b; Leon et al., 1996; Lithell et al., 1996; Moore et al., 1996; Forsen et al., 1997; RichEdwards et al., 1997).