Infectious Diseases in Aged Population

An emerging public health challenge is to protect the growing ageing population from infectious diseases, which can significantly impact the quality of life of those affected.

The vulnerability of this age group is related to impaired host defenses such as diminished cell-mediated immunity. Lifestyle considerations, e.g., travel and living arrangements, and residence in nursing homes, can further complicate the clinical picture.

The increasing number of persons >65 years of age form a special population at risk for nosocomial and other health care-associated infections. The vulnerability of this age group is related to impaired host defenses such as diminished cell-mediated immunity. Lifestyle considerations, e.g., travel and living arrangements, and residence in nursing homes, can further complicate the clinical picture. The magnitude and diversity of health care-associated infections in the aging population are generating new arenas for prevention and control efforts.

Common infections leading to hospitalizations in this age group result in respiratory infections and bacteraemia and the impact of these infections on the quality of life in aged populations has not been accurately quantified in a European setting.

This study aims to capture and quantify the impact of infectious diseases on quality of life in an aged population.

The IMI European public-private partnership created the VITAL project (Vaccines and infectious diseases in the Ageing populations) to assess the infectious diseases burden and mechanisms of immunosenescence in the ageing populations. This aims to provide evidence-based knowledge on vaccination strategies to establish healthy ageing. The project articulates around five work packages and this study comes within the frame of the first one. The expected results of this work combine with and complete the retrospective assessment already done on the available datasets/databases.

The decreased efficiency of the cell-mediated immunity and more generally the immunosenescence make the ageing population prone to harming infectious diseases. That combined with the growth of the ageing populations make healthy ageing a major and current challenge to address. The common infections leading to hospitalizations in this age groups include respiratory infections and bacteremia.

Acute respiratory infections (ARI) are a leading cause of hospitalizations and death in the aged adult population. They can be caused by viruses (Influenza for instance), bacteria (Streptococcus pneumoniae for instance) and fungi, with either a single or a co-infection. Viruses and bacteria have a comparable share in causing ARI, and a significant part of them are vaccine preventable pathogens. Although the burden of ARI is highest in the ageing population, vaccine effectiveness is the lowest in this vulnerable population, mostly because of immunosenescence. This issue can be tackled by increasing vaccine coverage and efficiency and developing vaccines and treatments for the pathogens leaving physicians with limited prevention and therapeutic options.

Bacteremia is defined by the presence of viable bacteria in the circulating blood generally causing fever, chills, tachycardia, tachypnea, and sometimes requiring hospitalization. It increases morbidity and has a high mortality rate in all ageing populations. It is mostly caused by Gram negative (E. Coli, Proteus mirabilis, Klebsiella) but also by Gram positive bacteria (Staphylococcus aureus). Along with its high burden in this population, bacteremia is difficult to tackle because of an odd and nonspecific clinical presentation. In addition, bacteremia is associated with comorbidities, underlying diseases and long-term care centres stays. The increasing proportion of antimicrobial resistance such as methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Staphylococcus aureus (VRSA) or extended spectrum beta-lactamase (ESBL) make complete eradication harder in a given patient and may alter his quality of life in a durable way.

There is a high ARI and bacteremia burden in the aged population in terms of morbidity and mortality. This burden is also believed to be expressed in terms of lower quality of life, and increased frailty and disability and has begun to be assessed in either of the two pathologies.

The impact of ARI and/or bacteremia on those components needs to be assessed in the most comprehensive way as the investigator are facing a specific population: a significant part of the ageing population is already relatively frail. Frailty has been demonstrated as a predictor of bad recovery after an ARI hospitalization in older adults, of being an adverse outcome of acute illness and of being associated with diminished vaccine effectiveness.

The impact of ARI and bacteremia hospitalization on quality of life, frailty and disability in that ageing population has not been assessed in a wide European setting to our knowledge. Filling this data gap will strengthen the evidence-based and guide public health policies concerning vaccination strategies to promote healthy ageing.