When the incidence trends were evaluated by age groups based on life stages (0–19, 20–44, 45–64 and + 65 years), there was stable and constant increase in incidence for both females and males. For women, the APCs varied very little. For men, the highest APC was observe among the youngest group (20 to 44 years). As it is a pathology with a multifactorial origin, factors such as increase of weight secondary to changes in dietary patterns and sedentary lifestyle may be contributing to this increase(12). In countries with a very high human development index (HDI), such as the United States, a decrease in the incidence rates of CRC among individuals older than 50 years is being observed, but other groups are showing increasing and constant APCs of 2.7 (< 40 years) and 1.7 (40 to 49 years) (13). The decrease among individuals over 50 years is most likely due to public health policies (13). Because CRC is largely preventable, screenings reduce the incidence among the elderly; however, as screening is performed earlier, the incidence in the younger population increases(14).
Regarding mortality, there was a stability regarding the trends for men and women over 65 years, between 45 and 64 years and all ages. The literature has shown for regions with an HDI similar of Brazil, the incidence and mortality trends of CRC have been increasing(15). This reflects the difficulty of access to healthcare, with consequent advanced stages at diagnosis (16, 17), in addition to poor infrastructure, lack of adequate screening and treatment (18), and age-related comorbidities (19).
During the studied period, there was a higher proportion of incident and death cases among women than men (59.5% x 40.5% and 57.4 × 42.6%, respectively). This finding differentiates the reality of the studied population from the results obtained by Ansa et al. (13), who evaluated data from the Surveillance, Epidemiology, and End Results (SEER) Program and observed that CRC was more prevalent among men from 2000 to 2014 in the United States. This difference occur because of the different proportions between men/women in the two regions of study (20, 21). In the state of Sergipe, referring to the 2010 census, for older than 40 years, the male:female ratio was 1:1.16, while in the United States this same ratio for the period was 1:1.09 (20, 21).
When the adjusted incidence rates were analysed, we observed that for the female and male sex, there was a similar, however intermediary variation in the adjusted rate for the world population. These intermediate values occurred due to the epidemiological transition observed in countries with a lower HDI. The highest incidence rates are concentrated in regions with higher HDI, for example, Australia and New Zealand (36.7 cases per 100,000), Europe (28.8–32.1 cases per 100,000), East Asia (26.5 cases per 100,000) and North America (26.2 cases per 100,000) (22). In regions with lower HDI, such as Africa and South-Central Asia, there are lower incidence rates (6.4–9.2 per 100,000 and 4.9 per 100,000, respectively) (22).
For both sexes, the left colon and rectum were the most common sites of CCR (Table 1). The epidemiological relevance of these data results from the fact the most common sites are accessed by flexible rectosigmoidoscopy, which may be a less expensive and more effective screening measure for economically and socially less-developed countries. Ahnen et al. (23) observed a higher prevalence of CRC in the left colon and rectum in the US in 2014, especially among younger individuals.
When the histological subtypes of CRC were considered, approximately 94.5% of the CRCs were adenocarcinoma for both sexes. These values are similar to those described in the international and American literature, in which more than 90% of CRCs are adenocarcinomas (24).
The Kernel Map showed a distribution of the hotpoints in the northeastern region. This result may have accurred due the higher population densities, referring to the 2010 census, located in this region (25). When analyzing the hotpoints taking into account the 2000 census, there was a small change in the population density (25). When assessing the monthly household income distributed bu neighborhood using the 2000 census data as a reference, it is observed that the neighborhoods with the highest monthly household in come values are included in the hotpoints of the entire period studied (1996–2015) (25, 26).This corroborates the relationship between a higher HDI and a higher incidence (27). The neighborhoods with the lowest monthly incomes are also found in the hotpoint areas due to their proximity to the more affluent areas and, mainly, due to their population density.
The strengths of our study was: a long serie times (1996–2015); incidence data validated nationally and internationally with the data base quality showing a diagnose with microscopic verification 94.8%; the death certificate only cases 3.5% and C80 1.6%.