Parents of boys age faster than parents of girls.
A new Columbia University study has found mothers and fathers of sons see their brain power drop away more quickly as they grow older.
Researchers say the more boys in a family, the worse the damage, with the effects being blamed on girls typically being more caring than boys and helping their parents stay healthy.
Parents of boys weren't any more or less clever at the start of an 18-year study, but as their children aged they scored lowered in intelligence tests than parents of girls at the same age.
