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

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

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.

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).

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.