LRTI and CAP incidence underestimated in oldest citizens

Data from the UK indicate that statistics on lower respiratory tract infection (LRTI) and community-acquired pneumonia (CAP) in the over 65s probably underestimate their burden in the oldest patients.

In the study, which included data on 1,534,443 general practice older adult patients, those aged 85 to 89 years had a rate of LRTI double that of those aged 65 to 69 years, and seven times more episodes of CAP.

And the research team, from the London School of Hygiene and Tropical Medicine, observed that rates of the two infections increased over the course of their study from April 1997 to March 2011, largely due to the aging population.

Unlike most other studies on respiratory infection incidence, the team linked up general practice and hospital data to distinguish cases of CAP from hospital-acquired pneumonia, and stratified those aged over 65 years, a standardized grouping which they say is increasingly irrelevant.

“This is a disparate group, including people working full-time and those that require round-the-clock care,” comment authors Elizabeth Millett and colleagues.

They found that rates of LRTI increased over time, but this was attenuated when they stratified for age, suggesting that it was largely due to population aging. When stratified by age, LRTI incidence was 187.9 cases per 1000 person–years in those aged 85 to 89 years compared with just 92.2 cases per 1000 person–years in those aged 65 to 69 years.

The difference in CAP rates according to age was even more marked, with an incidence of 21.8 episodes and 2.8 episodes per 1000 person–years in each age group, respectively; and similar to LRTI, the increased incidence over time was attenuated by age stratification.

Millett and colleagues therefore conclude that summary estimates of LRTI and CAP rates in the over 65 age group considerably underestimate their incidence in the oldest age groups.

“Routine data such as these are used in many countries to assess disease burden,” they write in PLoS One.

“Given our findings, our methodology is likely to be highly relevant to other countries with aging populations, so that they can obtain more accurate incidence estimates of these important infections,” they conclude.

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