Variations of Pityrosporum orbiculare in middle-aged and elderly individuals.

Pityrosporum orbiculare was cultured from clinically normal skin in 60 adults, 30 to 80 years of age. Antibody titers against P. orbiculare in serum and lipid measurements were also estimated. There was a parallel between a reduction in number of cultured organisms and an increase in age (p = 0.002, multiple linear regression analysis). The lipid content of the skin in older people was lower than that in young and middle aged (p = 0.0002). This may be an explanation for the decrease in number of P. orbiculare on the skin in elderly individuals. Antibody titres decreased significantly as age increased (p = 0.02). One explanation may be a reduced stimulation of the immune system due to a drop in the number of organisms.