Half of all age related macular degeneration could be genetic

Age related macular degeneration is an important cause of blindness among older people, particularly in developed countries. The aetiology is still unclear, but a new study suggests that about half of all cases are caused by polymorphism at the gene coding for complement factor H, an important inflammatory mediator that inhibits the complement cascade.

In a cohort of people aged over 55 from Rotterdam in the Netherlands, carriers of the Y402H allele were significantly more likely than non-carriers to develop age related macular degeneration over a median follow-up of 10 years. They were also more likely to get worse. People homozygous for the allele had an 11-fold increase in risk of sight threatening degeneration (odds ratio 11.02; 95% CI 6.82 to 11.81), relative to non-carriers. Overall, 36.2% (4116/11 362) of the cohort carried at least one allele. Genetic predisposition became more important after the age of 75, and the authors estimate that nearly half the homozygotes in their cohort would develop a sight threatening form of the disease by the age of 95.

Smoking is a well known risk factor for age related macular degeneration, but in this study it was particularly risky for people with an existing genetic predisposition. Homozygotes for the Y402H allele were over 30 times more likely to develop serious age related macular degeneration than non-carriers who did not smoke (odds ratio 34.0; 13.0 to 88.6).

Obese adolescents are more likely to die young

Being overweight or obese at age 18 increases your chances of a premature death, according to a cohort study of over 100 000 American nurses. Even nurses who remembered being only moderately overweight at 18 had an increased risk of dying before late middle age (hazard ratio 1.66; 95% CI 1.31 to 2.10 for a body mass index of 25.0 to 29.9 relative to …