Which patient is most at risk for developing pneumonia?

Pneumococcal disease [including community-acquired pneumonia and invasive pneumococcal disease] poses a burden to the community all year round, especially in those with chronic underlying conditions. Individuals with COPD, asthma or who smoke, and those with chronic heart disease or diabetes mellitus have been shown to be at increased risk of pneumococcal disease compared with those without these risk factors. These conditions, and smoking, can also adversely affect patient outcomes, including short-term and long-term mortality rates, following pneumonia. Community-acquired pneumonia, and in particular pneumococcal pneumonia, is associated with a significant economic burden, especially in those who are hospitalised, and also has an impact on a patient's quality of life. Therefore, physicians should target individuals with COPD, asthma, heart disease or diabetes mellitus, and those who smoke, for pneumococcal vaccination at the earliest opportunity at any time of the year.

• Bacterial Infection
• Pneumonia
• COPD Exacerbations
• Asthma

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• Bacterial Infection
• Pneumonia
• COPD Exacerbations
• Asthma

Introduction

Pneumococcal disease in adults, including community-acquired pneumonia [CAP] and invasive pneumococcal disease [IPD], is a global problem, especially in individuals with chronic diseases such as COPD, diabetes mellitus and chronic heart disease [CHD]. Due to the chronic nature of these conditions, affected individuals are at risk of CAP and IPD all year round, not only during the winter, unlike seasonal influenza.

This review addresses two key questions concerning the burden of pneumococcal disease to help physicians target vaccination to appropriate individuals: who is at increased risk of CAP and IPD; and what are the effects of risk factors on the severity and prognosis of pneumococcal disease? It also highlights the economic burden of pneumococcal disease, the impact of pneumococcal disease on underlying comorbidities, and the importance of timely vaccination. We have focused primarily on COPD, asthma, smoking, diabetes and/or CHD as these are common risk factors for pneumococcal disease in primary practice. There are, however, many other risk factors. As Streptococcus pneumoniae is the most frequent cause of CAP irrespective of age and comorbidity, , information has been provided on all-cause pneumonia [ie, CAP] and pneumococcal pneumonia.

Search methodology

A broad search strategy was used to find English language publications in human adults indexed on PubMed [2004–November 2014]. Relevant publications were manually selected from the following searches: pneumonia AND risk factor, CHD AND pneumonia, diabetes AND pneumonia, lung disease AND pneumonia, asthma AND pneumonia, COPD AND pneumonia, tobacco OR smoking AND pneumonia, and economic data AND pneumonia. Data comparing the risk of pneumococcal disease in adults with the above risk factors versus those without risk factors were tabulated [excluding publications prior to 2008 or with data prior to 2000], and these data used to discuss the risk of pneumococcal disease in individuals with these risk factors.

Populations at risk of pneumococcal disease

Individuals with COPD, asthma or who smoke, and those with CHD or diabetes mellitus, are at increased risk of pneumococcal disease [CAP and IPD] compared with those without these risk factors. , Similar rate ratios for all-cause pneumonia [CAP], pneumococcal pneumonia and IPD have been reported in individuals with comorbidities [versus those without comorbidities].

Chronic respiratory diseases

Patients with chronic respiratory disease [COPD, chronic bronchitis and/or asthma] are at a higher risk of CAP and IPD than individuals without these comorbidities with fold increases of between 1.3 and 13.5 for CAP and 1.3 and 16.8 for IPD [OR; ; see online supplementary table S1]. , , , ,

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Table 1

Overview of risk factors associated with community-acquired pneumonia and pneumococcal disease

Risk of CAP varies with condition and age, with older individuals [≥65 years of age] with COPD being at especially high risk. Among individuals with COPD, those aged 65–79 or ≥80 years have been shown to have an increasingly higher risk of CAP than those aged 45–65 years. Having COPD, and greater age, lack of pneumococcal vaccination, and corticosteroid therapy have been identified as independent factors for recurrent CAP in adults.

The severity of the underlying respiratory condition affects the risk of CAP. , , Individuals aged ≥65 years who have mild lung disease [not requiring medication or oxygen] have been shown to be twice as likely to have CAP as those without lung disease, whereas those with severe lung disease [requiring oxygen] are eight times more likely to have CAP. Similarly, moderate and severe lung disease [percentage predicted FEV1: 50–80% and 150 pack-years and 1.01 for ≤150 pack-years]. Among the ex-smokers, those who had stopped smoking >4 years ago had a significantly reduced risk of CAP than those who had stopped smoking 65 years who had never smoked but were exposed to passive smoking were also at significantly increased risk of CAP [OR adjusted for age and sex: 1.56]. Similarly, in a separate study, individuals aged ≥65 years who were exposed to passive smoke at home had an increased risk of CAP [relative risk [RR]: 1.48 vs those not exposed to passive smoke].

In another study in individuals aged ≥65 years, current smokers had a higher risk of CAP than ex-smokers irrespective of age [OR for all ages: 1.8 vs 1.3]. Based on the population attributable fraction, which is a measure of the proportion of cases attributed to a particular risk factor, Jackson et al calculated that 2.4% of CAP cases are due to current smoking, increasing to 5.5% of cases in those with no cardiopulmonary disease. In contrast, in a study involving individuals with COPD, current smoking was not found to affect CAP incidence, which the authors attributed to inaccurate recording of current smoking status [20% of individuals were reported to have never smoked], other causes of COPD such as occupational exposures, or individuals with severe COPD ceasing to smoke.

The effect of smoking status on IPD incidence is variable, , , , which may reflect the variable prevalence of smoking within different populations. In US adults with chronic medical conditions, Shea et al calculated rate ratios of 3.6 in smokers aged 18–49 years to 4.3 in those aged 50–64 years.

In another US study, the risk of bacteraemic pneumococcal pneumonia in adults was significantly higher in current smokers than in those who have never smoked or are not currently smoking [multivariate adjusted OR: 2.2]. Smokers were also shown to be 3.7 times more likely to develop pneumococcal bacteraemic pneumonia than non-smokers in an Australian study. In contrast, former or current smoking was not associated with IPD in Navajo adults in whom the prevalence of smoking was low.

Diabetes mellitus

Patients with diabetes have an increased risk of up to 1.4 for CAP and ranging from 1.4 to 4.6 for IPD [ORs; ; see online supplementary table S3]. , , , , , , Analysis of long-term UK data suggests that the risk of lobar pneumonia, pneumococcal pneumonia, septicaemia and meningitis in patients hospitalised with diabetes declined little between 1963 and 2011. However, a decreased risk of pneumococcal disease was observed in individuals aged /=50 years. Appl Health Econ Health Policy 2013;11:251–8. doi:10.1007/s40258-013-0026-0

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