This study analyzed the seasonality of peritonsillar, retropharyngeal, and parapharyngeal abscesses according to the patient’s sex and age group. The number of peritonsillar, retropharyngeal, and parapharyngeal abscesses was highest in winter and spring and lowest in summer in the 2010–2019 period. Additionally, female predominance in these diseases was observed. The highest numbers of peritonsillar abscesses were reported in patients aged < 10 years, whereas retropharyngeal and parapharyngeal abscesses were most prevalent in patients aged 30–39 years.
A peritonsillar abscess is a collection of pus between the pharyngeal constrictor muscle and tonsillar capsule, and constitutes the most common deep neck space abscess type [6]. The majority of medical textbooks describe a peritonsillar abscess as a complication of acute tonsillitis [7]. Group A Streptococcus (GAS) and Fusobacterium necrophorum (FN) are both prevalent pathogens in the peritonsillar abscess [8]. Klug et al. found that the ratio between GAS and FN was highly dependent on the season (FN > GAS and GAS > FN in summer and winter, respectively) [8]. In addition, the relative incidence of GAS- and FN-infected patients with peritonsillar abscesses was highly dependent on age. Our study found an increased incidence of peritonsillar abscesses from winter to spring in all age groups. However, patients younger than 9 years showed an increased incidence in spring and summer.
Previous studies on deep neck abscesses have shown that the male-to-female ratio varies from male predominance [9] to female predominance [1]. In our study, we observed female predominance with a male-to-female ratio of 1:1.25. Peritonsillar abscesses commonly occur in adults aged 20–40 years [10]. Our study showed a peak distribution of peritonsillar abscesses in patients under 10 years of age, followed by patients aged 30–39 years. Frequent hospital visits at a young age (< 10 years) are thought to be related to the age distribution of patients with peritonsillar abscesses.
Retropharyngeal and parapharyngeal abscesses are often termed deep neck space abscesses, arising at one of two adjacent anatomical spaces in the neck [2]. The mean annual incidence rate of retropharyngeal and parapharyngeal abscesses has increased in recent years [11, 12]. Our study also showed an increasing tendency for retropharyngeal and parapharyngeal abscesses in the 2010–2019 period. The seasonality of retropharyngeal and parapharyngeal abscesses (with predominance in winter-spring) reported here supports the findings of another study on pediatric patients (≤ 20 years old) from the Kids’ Inpatient Database of US 2003–2012 [13]. Female predominance (1:1.34) was observed for retropharyngeal and parapharyngeal abscesses in that study, similar to our observations of peritonsillar abscesses. The peak distribution of retropharyngeal and parapharyngeal abscesses was 30–39 years, unlike that of peritonsillar abscesses. Analysis of additional risk factors for deep neck space abscesses will be necessary to determine the cause of these differences.
In this study, patients with deep neck space abscesses showed similar seasonality (highest in winter) but slightly different aspects (different usual age and peak). The common predisposing etiologic factor of deep neck space abscesses might be upper respiratory infection (common cold), pharyngitis, and tonsillitis. However, peritonsillar, retropharyngeal, and parapharyngeal abscesses are caused by slightly different causes in different predisposing age [14]. Incidence of peritonsillar abscess is associated with increasing acute tonsillitis in winter seasons. The occurrence of retropharyngeal and parapharyngeal abscesses in older ages is highly associated with dental manipulation as well as tonsillitis [15]. The common etiologic factors in children for retropharyngeal abscess are upper respiratory tract infections [16]. In addition, the origin of parapharyngeal abscess remains unknown because the sore throat may clear by the time of presentation.
In this study, detailed monthly climate data were acquired from the Korean Meteorological Administration and analyzed to determine the association between climate factors and deep neck space abscesses. A previous study showed that peritonsillar abscesses were positively correlated with monthly average and maximum temperatures and were not correlated with relative air humidity and precipitation [1]. However, that study was conducted on patients admitted to one tertiary hospital and differed from the present study on outpatients. Another previous study showed that peritonsillar abscesses were not correlated with meteorological conditions such as temperature and humidity [17]. However, that study did not analyze the entire Korean population, but only a sample cohort from the Korean Health Insurance dataset, and observed differences between patients and normal groups. In the current study, we analyzed climate data and corresponding patient data in one country during every month in a 10-year period, and found that peritonsillar abscesses were negatively correlated with several climate factors, including average temperature, ground temperature, relative humidity, and precipitation. In contrast, daily temperature range and monthly PM10 were positively correlated with peritonsillar abscesses. In this line, PM10 affects host defense mechanisms and is associated with various airway diseases [18].
In addition, the association between climate factors and retropharyngeal and parapharyngeal abscesses has not been discussed to date. Our study showed that retropharyngeal and parapharyngeal abscesses are characterized by a comparable degree of seasonality as peritonsillar abscesses. Retropharyngeal and parapharyngeal abscesses were also correlated with several climate factors, including average temperature, ground temperature, relative humidity, precipitation, and daily temperature. PM10 showed a weaker correlation with retropharyngeal and parapharyngeal abscesses than with peritonsillar abscesses. Instead, the sunlight rate showed a strong correlation with retropharyngeal and parapharyngeal abscesses. We hypothesize that this observation is related to the stronger seasonality of retropharyngeal and parapharyngeal abscesses compared to peritonsillar abscesses.
Our study is not free from certain limitations. First, the utilized medical claims database uses diagnostic coding rather than medical chart records. Second, there is a lack of information on other social factors, such as medical history, smoking, and alcohol consumption history, that may affect the incidence of deep neck abscesses. However, the medical claims database included most patients in Korea, significantly reducing the selection bias. Finally, the unique characteristics of each region could not be considered because the monthly climate data used were the national average data of the whole of Korea.
To the best of our knowledge, this is the first study to comprehensively analyze the seasonality and climatic relevance of neck space abscesses using a large population database and meteorological data. We focused not only on determining the seasonality of peritonsillar, retropharyngeal, and parapharyngeal abscesses, but also on determining their correlation with detailed climate data in the period of 10 years.