Methods:
We searched MEDLINE and EMBASE databases for population-based studies reporting the incidence of appendicitis or appendectomy. Time trends were explored using Poisson regression and reported as annual percent change (APC) with 95% confidence intervals (CI). APC were stratified by time periods and pooled using random effects models. Incidence since 2000 was pooled for regions in the Western world.
Results:
The search retrieved 10,247 citations with 120 studies reporting on the incidence of appendicitis or appendectomy. During the 21st century the pooled incidence of appendicitis or appendectomy (in per 100,000 person-years) was 100 (95% CI: 91, 110) in Northern America, and the estimated number of cases in 2015 was 378,614. The pooled incidence ranged from 105 in Eastern Europe to 151 in Western Europe. In Western countries, the incidence of appendectomy steadily decreased since 1990 (APC after 1989=−1.54; 95% CI: −2.22, −0.86), whereas the incidence of appendicitis stabilized (APC=−0.36; 95% CI: −0.97, 0.26) for both perforated (APC=0.95; 95% CI: −0.25, 2.17) and nonperforated appendicitis (APC=0.44; 95% CI: −0.84, 1.73). In the 21st century, the incidence of appendicitis or appendectomy is high in newly industrialized countries in Asia (South Korea pooled: 206), the Middle East (Turkey pooled: 160), and Southern America (Chile: 202).
Conclusions:
Appendicitis is a global disease. The incidence of appendicitis is stable in most Western countries. Data from newly industrialized countries is sparse, but suggests that appendicitis is rising rapidly.
The incidence of appendicitis escalated in Western countries during the 1900s1 until without explanation the incidence decreased in the mid-part of the 20th century.2 In contrast, appendicitis was relatively uncommon outside Western countries during the 20th century. However, at the turn of the 21st century newly industrialized countries are reporting a rising incidence of appendicitis.3,4
Understanding the global evolution of appendicitis in highly industrialized countries and in newly industrialized countries is necessary for planning healthcare resource utilization. In Western countries appendicitis is associated with morbidity, mortality and significant costs to the healthcare system.5 The life-time risk of appendicitis is 1 in 15 in the United States.5 One third of appendicitis cases present to hospital with a perforated appendix.6 Appendicitis-related hospitalizations cost $3 billion in 1 year within the United States alone.7 However, the impact of appendicitis on healthcare systems may need to be reevaluated in the context of changing epidemiological patterns throughout the world.
Moreover, the rising incidence of appendicitis in newly industrialized countries may indicate an outbreak of appendicitis outside Western countries. The clinical infrastructure in newly industrialized countries may need to be restructured to mitigate morbidity and mortality of appendicitis. Furthermore, contrasting the incidence of appendicitis between Western countries and newly industrialized countries may offer clues to the underlying environmental underpinning of appendicitis. By identifying environmental triggers of appendicitis, public policy initiatives can be instituted to modify environmental exposures that prevent appendicitis.
Thus, we conducted a systematic review of population-based studies reporting the incidence of appendicitis across the world, performed temporal trend analyses of incidence rates over the past century, and pooled incidence of appendicitis since the beginning of the 21st century.
Search Strategy
We conducted a systematic review following the meta-analysis of observational studies (MOOSE) guidelines.8 A systematic literature search of MEDLINE (1950 to June 3, 2015) and EMBASE (Excerpta Medica Database; 1980 to June 3, 2015) databases was conducted for population-based studies reporting the incidence of appendicitis. The search strategy is described in Appendix 1. The search was not limited by language. The reference lists of relevant studies were also reviewed. When possible, authors were contacted to answer questions.