Key Point

Small airway particle clearance over 21 days decreases with age; the decline may contribute to the increased incidence of respiratory symptoms in the elderly.

STOCKHOLM—Long-term particle clearance from the small airways decreases with age, a recent study has shown.¹ It is reasonable to suggest that this age-related decline could be a factor in the relatively high rate of respiratory symptoms among the elderly, the study authors said. Lead author Magnus Svartengren, MD, PhD, is Head of the Division of Occupational Medicine at the Karolinska Institute in Stockholm.

The clearance of large (6 µm) radiolabeled Teflon particles from the small airways over 21 days was measured with whole-body plethysmography in 46 healthy nonsmoking adults ages 19 to 81. These individuals inhaled the Teflon particles at an extremely slow rate of 0.05 L⋅s^-1, a technique shown in theoretical models to deposit particles mainly in the smallest ciliated airways. The study focused on the small airways because they “are probably the most important or sensitive region in chronic respiratory diseases, such as chronic bronchitis and asthma,” the authors explained.

Significant relationships were found between individual 24-hour large airway clearance (expressed as a percentage of initial particle deposition in the lungs) and age, FEV₁, and FVC; these findings are consistent with those of previous studies. As expected, age was strongly associated with FEV₁, percent predicted FEV₁, and FVC. “Using stepwise linear regression, including age and FEV₁ or FVC, only age remained significantly associated to clearance,” reported the authors.

Most importantly, large and small airway particle clearance decreased significantly with increasing age. The negative association between age and small airway clearance was significant at all time points after 24 hours (measurements were taken at baseline, 24 hours, and seven, 14, and 21 days), but the relationship was clearer at later time points, the authors stated.

The study data did not permit any conclusions about whether decreased mucociliary function precedes a reduction in lung function or vice versa, noted the authors. They suggested that decreased pulmonary function and small airway particle clearance may be a part of normal aging.

“The present finding of slower long-term clearance in the elderly is interesting since chronic bronchitis is highly age dependent,” they remarked. “[Our] interpretation is that small airway clearance decreases with age, irrespective of whether symptoms are present or not.”

—Timothy Begany

Reference
1. Svartengren M, Falk R, Philipson K. Long-term clearance from small airways decreases with age. Eur Respir J. 2005;26:609-615.

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