Acute respiratory infections in elderly people: the role of micronutrients and lifestyle

Acute respiratory infections are the most frequent of all infectious diseases. In popular speech common cold, flu (influenza), and pneumonia all denote acute respiratory infections. Elderly people show an increased risk of these infections and their complications. In The Netherlands about 2.000 elderly people die annually from influenza and influenza-related illness. Because the number of elderly people is growing rapidly worldwide, factors that could diminish the risk of theinfections,may have great public health importance.This thesis focuses on the effects of micronutrients and lifestyle on acute respiratory infections in 652 apparently healthy well-nourished elderly people of 60-95 years. Our 15-months randomized controlled trial showed that neither multivitamins-minerals in doses near the recommended dietary allowance nor 200mg of vitamin E had beneficial effects on the incidence and severity of acute respiratory infections. Incidence rate ratio (95% confidence interval) was 0.95 (0.75-1.15) in groups that received multivitamins-minerals and 1.12 (0.88-1.25) in groups that received vitamin E. Instead, we observed unfavorable effects of vitamin E on illness-severity. In the vitamin E compared to the no vitamin E group, illness-duration was 19 versus 14 days (p=0.02); no. of symptoms was six versus four (p=0.03); presence of fever was 37% versus 25% (p=0.009); and presence of activity-restriction was 52% versus 41% (p=0.02). Episodes of respiratory infection were self-assessed by means of a diary and substantiated by nurse telephone check, home-visits, and microbiology and serology testing in a subset. Infections turned out to be laboratory confirmed in 58% of the patients, whereas in only four percent of persons without symptoms of infection a pathogen was identified. Major pathogens in patients suffering from acute respiratory infection were rhinoviruses (32%), coronaviruses (17%), and influenzaviruses(7%).In addition, observational analyses were performed using the data of the trial. High plasma beta-carotene concentrations may reduce the incidence of acute respiratory infections, whereas alcohol consumption may increase the risk. Observational studies are however sensitive to bias and the influence of plasma carotenoids and lifestyle factors, i.e. alcohol consumption, smoking, and physical activity, on acute respiratory infections remain therefore subject to debate. Our main conclusion is that relatively healthy, well-nourished elderly people will not benefit from multivitamin-mineral and vitamin E supplementation in reducing acute respiratory infections.