Influence of age, gender and smoking on Streptococcus pneumoniae, Haemophilus influenzae and Moraxella (Branhamella) catarrhalis antibody titres in an elderly population.

The purpose of this study was to investigate the association of serum antibody levels to Streptococcus pneumoniae, Haemophilus influenzae and Moraxella (Branhamella) catarrhalis with age, gender and smoking in an elderly population. The study population comprised all the inhabitants aged 65 years or over in a rural municipality in south-western Finland. Serum samples were obtained from 1,174 out of a total of 1,360 subjects. Bacterial antibodies were measured by enzyme immunoassay (EIA) using pneumolysin and whole bacterial cells of H. influenzae and M. catarrhalis (mixture of 10 different strains for both) as antigens. The main findings were as follows: (i) antibody levels generally decreased with increasing age both in men and in women; (ii) antibody titres against H. influenzae and M. catarrhalis were higher in men than in women; and (iii) antibody titres to H. influenzae and M. catarrhalis, but not to S. pneumoniae, were significantly higher in smokers than in non-smokers. These data suggest that antibody-mediated protection against respiratory pathogens may be impaired in the elderly, leading to a higher susceptibility to respiratory tract infections, that the exposure to H. influenzae and M. catarrhalis may be higher in men than in women, and that smokers have more respiratory infections or colonization due to these 2 bacteria than do non-smokers.