I recently came across a new term that I suspect we may hear more of. The term ‘weathering’ has been adopted by many in the scientific community to describe the effect of ongoing external factors during everyday life that influence differences in the expression of certain traits, including disease. This has been on my mind while listening to lectures on global myopia distribution during last weekend’s BCLA conference, while working on this week’s CET on lifestyle impact upon eye disease (page 24), and while reading some of the excellent materials about diabetes just released for Diabetes Week.

The generally held view, that there are separate classes of ethnicity, races if you must, is a simplistic and reductivist view, one that Richard Dawkins wonderfully stated was due to the ‘tyranny of the discontinued mind.’ Human DNA is remarkably constant across the globe, and variations in the sequence of clusters of genes or which genes are activated or dormant is fluid, much more so now than in ancient times when localisation and social constraints supported gene pooling. So, it should not surprise us that there is greater genetic variation among North American white people than between Europeans and Africans.

Most common eye diseases have many risk factors and only some are modifiable. Non-modifiable ones include, for example, age, gender and the contentious ‘ethnicity’. Some might be classed as direct, like age for glaucoma, or indirect, like microvascular circulation for glaucoma. Now, African ethnicity is a risk factor for primary open-angle glaucoma. Weathering might explain that this is, at least in part, related to differences in socioeconomic factors, poorer diet, smoking habit, poor access to healthcare and, importantly after a century of greater integration of different phenotypes, daily stresses resulting from poor social treatment and societal bias.

Controlling for variables in research is problematic, but has to be attempted. I suggest that much of the ethnic variation in eye disease risk has at least some influence from weathering. Discuss.