The effect of aging on nasal mucociliary clearance, beat frequency, and ultrastructure of respiratory cilia

The increased susceptibility of the elderly to lower respiratory tract infe ction cannot be fully explained. Although mucociliary clearance, which is a ffected by ciliary beating and ultrastructure, plays a crucial role in the defense of the airways against inhaled microbes, little is known of the eff ects of aging on these parameters. We studied the nasal mucociliary clearan ce (NMCC) time, ciliary beat frequency, and ultrastructure of respiratory c ilia in a cohort of healthy volunteers (age range 11 to 90 yr). Ciliary bea t frequency of ciliated nasal epithelial cells was obtained via an establis hed photometric method, and NMCC time was measured with the saccharine test . There was a correlation of ciliary beat frequency (r = -0.48, p = 0.0001) and NMCC time r = 0.64, p < 0.001) with increasing age. Transmission elect ron microscopy revealed an increase in the percent of subjects exhibiting m icrotubular disarrangement and single central microtubules with aging (p = 0.002 and p = 0.005, respectively). Subjects older than 40 yr of age had si gnificantly slower ciliary beat frequency, higher percent of ciliary cross- sections displaying single tubules, and longer NMCC time than their younger counterparts (p < 0.05), These findings may help explain the frequent occu rrence of respiratory infection in the elderly.