We've talked a lot about inbreeding and the its health consequences many many times before 'round these parts. Most people think of the consequences in terms of unmasking recessive disorders like rare bith defects or the inability to feel pain. But the consequences are also apparent in complex traits--a new article shows a negative correlation between heterozygosity in the genome (inbreeding causes decreased heterozygosity) and both blood pressure and cholesterol levels.

These findings, if replicated, suggest that hR [heterozygosity] be considered as a genetic risk factor in genetic epidemiological studies on common disease traits. They are consistent with the well-known effects of heterosis (hybrid vigour) described when outcrossing animals and plants. Outbreeding resulting from urbanization and migration from traditional population subgroups may be leading to increasing hR and may have beneficial effects on a range of traits associated with human health and disease. Other traits, such as age at menarche, IQ and lifespan, which have been changing during the decades of urbanization, may also have been influenced by demographic factors.