Respiratory tract infections are the most common type of infections managed by health care providers, and they are of great consequence.

In a recent report from the Centers for Disease Control, respiratory tract infections (upper respiratory tract infections, otitis, and lower respiratory tract infections) accounted for 16% of all outpatient visits of patients to physicians.

Of all the respiratory infections, sinusitis is one of the most common illnesses that affect a high proportion of the population.

According to the National Ambulatory Medical Care Survey data, sinusitis is the fifth most common diagnosis for which an antibiotic is prescribed. Sinusitis accounted for 9% and 21% of all pediatric and adult antibiotic prescriptions, respectively, written in 2002.

Since many cases of sinusitis are viral in etiology, these data actually suggest that antibiotics are frequently misused for the management of this illness. Such inappropriate use leads to increased resistance among respiratory tract pathogens.

The inappropriate use of antibiotics is related in part to the fact that sinusitis has been a relatively poorly defined clinical syndrome which is often a self-limited illness associated with wide variations in presenting symptoms, and an incomplete understanding of the pathogenesis and clinical course of the disease.

However, recent classification of the sinusitis syndrome as well as the publication of evidence-based guidelines has provided a clear approach to its management. The appropriate classification of sinusitis as well as an awareness of its epidemiology can facilitate better management of this infection.

The true prevalence of rhinosinusitis is unclear since various types of sinusitis are often lumped into this single designation. The true prevalence rate likely varies considerably from the diagnostic rate because not all individuals seek care for rhinosinusitis, and because of the inconsistencies in definitions.

Nonetheless, available statistics confirm a high overall prevalence and disease burden. Estimates of the prevalence of acute rhinosinusitis can be extrapolated based on its association with the common cold.

A reasonable estimate is that each adult has two to three colds per year, and each child has three to eight colds per year. Up to 80% of these upper respiratory illnesses may be associated with rhinosinusitis, equating to over one billion cases of rhinosinusitis annually in the United States.

It has been suggested that bacterial maxillary sinusitis complicates 0.5% to 2% of all upper respiratory tract infections, which translates into approximately 20 million cases of bacterial acute rhinosinusitis annually.

This estimate may understate the incidence of rhinosinusitis because the focus was on maxillary sinusitis. According to the 2001 National Health Interview Survey, 17.4% of the American adult population interviewed had been told by a doctor or health care professional that they had sinusitis in the past 12 months.

The prevalence of chronic rhinosinusitis may be better defined. According to the National Ambulatory Medical Care Survey, chronic sinusitis accounts for 12.3 million office visits to physicians, or 1.3% of total office visits annually.

Among Canadian adults, the reported prevalence of chronic rhinosinusitis is 5%. Unfortunately, the term chronic sinusitis is used to characterize a wide and possibly disparate group of inflammatory disorders, and this makes any specific approach to therapy problematic.

The economic impact of rhinosinusitis is considerable. In 1996, the direct cost due to sinusitis was $5.8 billion. A primary diagnosis of chronic rhinosinusitis accounted for more than 50% of all expenses.

To these costs, indirect costs need to be considered as well, such as days for work lost. Birnbaum et al. recently evaluated the economic burden of respiratory infection, including sinusitis, in an employed population to ascertain the impact of these infections from the perspective of the employer.

The investigators evaluated more than 63,000 patients with at least one diagnosis for a respiratory infection in 1997 who were identified in the claims database of a national Fortune 100 company.

Outcome measures were compared to those of a 10% random sample of beneficiaries in the overall employed population. The authors calculated a total cost of care that included not only direct health-care costs, but also disability costs and absenteeism costs.

Acute and chronic sinusitis represented the fifth and sixth most common respiratory tract infection with a total number of 9856 and 7368 patients, respectively. This compared to 10,852 treated for acute bronchitis, 5296 treated for chronic bronchitis, 4464 treated for pharyngitis, and 4036 treated for pneumonia.

The total aggregate employer cost for treating acute sinusitis and chronic sinusitis was $35,126,784 and $32,824,440, respectively (compared to $46,591,584 and $6,692,439 for pneumonia and pharyngitis).

In addition, sinusitis can adversely affect other aspects of quality of life. Matsui et al. observed an decline of cognitive function in elderly people using the Mini-Mental State Examination.

Chronic sinusitis may affect cognitive function either by decreasing the power of concentration or affecting specific cognitive functions, which can significantly have an impact on quality of life considerations.

Therefore, early medical intervention for chronic sinusitis should take into account this potentially neglected effect on cognitive function in the elderly.

Individuals with allergies or asthma and those who smoke may be predisposed to rhinosinusitis. For unclear reasons, rhinosinusitis affects more females than males. Women patients between the ages of 25 and 64 years were seenmost often.

When results were considered by single race without regard to ethnicity, Asian adults were less likely to have been told in the preceding 12 months that they had sinusitis compared with white, black, and American Indian or native-Alaska adults.

Adults in families that were not poor were more likely to have been told that they had sinusitis than adults in poor families. The percentage of adults with sinusitis was higher in the southern area of the United States than any other region.

Sokol recently reported results from a large study of sinusitis evaluated in the primary care setting, the Respiratory Surveillance Program. This study was undertaken over a 10-month period during the 1999–2000 respiratory infection season.

Patients were evaluated from 674 community-based practices for data including patient demographics and associated risk factors. The diagnosis of rhinosinusitis was based solely on the clinical judgment of the physician investigator.

Over 16,000 patients were evaluated and similar to data presented above, females predominated (almost a two to one ratio of female to male). Underlying conditions identified in this study included smoking, diabetes, and the presence of chronic lung disease.