Effects of age on neutrophil function and its relevance to bacterial infections in the elderly.

Abstract

Objective: To determine the effect of age on neutrophil function in patients with and without acute bacterial infections.

Method: Four groups of patients were recruited: Group 1: 15 elderly patients with infection (mean age 80.4 +/- 1.9 years), Group 2: 15 elderly control patients without infection (mean age 81.1 +/- 2.2 years), Group 3: 8 young patients with infections (mean age 26.7 +/- 2.9 years) and Group 4: 23 young controls (mean age 27.6 +/- 0.9 years). The main outcome measures included neutrophil counts and respiratory burst activation as measured by luminol enhanced chemiluminescence.

Results: Mean neutrophil counts were significantly higher in young patients with infections (5.04 +/- 0.96 x 10(9)/L) compared with young controls (2.63 +/- 0.33 x 10(9)/L) (p = 0.008) and in elderly with infections (6.51 +/- 0.97 x 10(9)/L) compared with elderly controls (4.1 +/- 0.88 x 10(9)/L) (p = 0.046). There was no significant difference between neutrophil counts of old and young patients (p = 0.40) or controls (p = 0.16). Mean peak luminol chemiluminescence was significantly increased in young patients (3329 +/- 284 mV) compared with young controls (1398 +/- 108 mV) and in elderly patients (2994 +/- 219 mV) compared with elderly controls (1674 +/- 197 mV) (p < 0.001). There was no significant difference between chemiluminescence activities of young and elderly controls (p = 0.41) or young and elderly patients (p = 0.14).

Conclusion: Age is not associated with a change in neutrophil number or activity in the absence of bacterial infection. Infection in both young and elderly produces a significant increase in neutrophil number and chemiluminescence activity.