This study described the temporal trend and identified the areas at risk of developing physical disability due to leprosy in Brazil over a twenty-one year time series. A variation in the trend was observed over the period, with three regions showing a decreasing trend and two showing a stationary trend in the coefficient of Grade 2 physical disability, suggesting the persistence of late-diagnosed cases. Despite global reductions in the detection rates of new leprosy cases [29–31], Brazil still reported more than fifty thousand new cases with grade 2 physical disability between 2001 and 2022.
The highest rates of new cases of leprosy with G2D were concentrated among adult males with black skin, low levels of education, and living in the northern and central-western regions of Brazil. National and international studies show a higher prevalence of the disease among men with lower levels of education, which may reflect social and economic inequalities, especially in neglected populations [32–39]. In general, men are more vulnerable to the disease and its more severe forms, often due to behaviours that make it difficult for them to seek appropriate health care, combined with a lack of specialized services to meet their specific needs [32, 40].
Patients with the multibacillary clinical form are more likely to develop physical disabilities. In our study, they accounted for 80.8 percent of the reported cases. The presence of leprosy disabilities is an indicator of late diagnosis and treatment [41–43]. This underscores the need to define and strengthen public health interventions aimed at early diagnosis and comprehensive care of people affected by M. leprae, especially those with severe forms of the disease, in order to reduce disability, mitigate associated stigma, and reduce disease transmission [42, 44–46].
The results show that there has been a decrease in the rate of new cases with G2D in Brazil. The Southeast, South and North regions showed a decreasing trend, while the Northeast and Central-West regions showed a stable trend. These results are consistent with other studies of leprosy conducted in Brazil, which have generally shown a reduction in the burden of leprosy in Brazil [45–47].
Roraima was the state with the highest rate of decline, from 54.9/1 million in 2001 to 9.4/1 million in 2022. A study conducted in this state between 2001 and 2017 showed a decrease in prevalence and case detection rates, demonstrating a trend toward elimination of the disease [48]. In an analysis measuring the severity of the disease in Brazil, Roraima, Paraíba, Rio Grande do Sul and Espírito Santo have better results in the fight against leprosy [49]. This decrease can be attributed to the implementation of the National Leprosy Control Programme in Brazil, which promoted and facilitated the decentralization of leprosy control to primary health care [46].
None of Brazil's state capitals showed an upward trend. Manaus/AM, Macapá/PA, Brasília/DF and the capital São Paulo/SP showed a downward trend. This finding may be related to two factors: (i) the ability of large centers to have better infrastructure and health care, which may facilitate early diagnosis [15], (ii) the higher hidden prevalence of the disease (50–52). This second factor seems to be the most appropriate to explain the stationary trend in the vast majority of capital cities. In São Paulo, for example, a study showed the hidden prevalence of the disease, whose real prevalence was six times higher than the observed prevalence [50]. The other Brazilian capitals show stationary behavior and some remain hyperendemic for leprosy, requiring additional efforts in the process of eliminating the disease [53, 54].
When analyzing the municipalities, endemicity fluctuated over the period analyzed, especially during the Covid-19 pandemic, where there was a decrease in the rates of new leprosy cases with G2D compared to previous years in the series. For example, in 2019, 14.5% (n = 807) of the municipalities had a rate > 10/million. In 2020, this percentage was 10.0% (n = 559). The Covid-19 pandemic has had an impact on diagnoses, increasing the hidden prevalence of the disease, as health systems in Brazil and around the world have turned their attention to controlling the pandemic, affecting the ability to maintain service provision and ensure adequate care for the population, especially for chronic and neglected diseases [15, 55–57].
The Covid-19 pandemic has created challenges in the follow-up and treatment of leprosy patients in primary health care centers throughout Brazil. This has led to delays in appointments, the need to reschedule appointments, treatment extensions due to drug shortages, and barriers to contact assessment and active case finding. These factors have had a negative impact on the leprosy program in all regions of the country [15, 55, 56, 58, 59].
The impact of the pandemic has been observed worldwide: the World Health Organization published a report showing a decrease in the number of countries and territories sharing leprosy statistics, from 166 (out of 221) in 2019 to 127 in 2020 and 143 in 2021, as well as a 37% global decrease in the detection of new cases of the disease [60]. Our study also noted the impact of the pandemic on high-risk areas: the number of municipalities in the high-high quadrant was lower than in the pre-pandemic years: 91 (1.6%) in 2020, 88 (1.6%) in 2021, and 59 (1.1%) in 2022.
Despite all the methodological care taken, this study has important limitations. First, it used secondary data from SINAN, which is directly influenced by the capacity of municipalities to detect and report new leprosy cases. In this way, the capacity of local surveillance services directly influences the records and thus the results of this study. Second, assessing the degree of physical disability is still a challenge for many municipalities, especially smaller ones with few human resources. Thus, the quality of the neurological examination and the degree of disability may influence the results.
Analysis and interpretation of these results are important for the development and evaluation of leprosy surveillance activities in Brazil. It suggests the need to strengthen active case finding and continuous monitoring of leprosy patients. These measures are essential to ensure an effective approach to control and to prevent the spread of the disease and its disabilities.
Our results show spatial inequalities in the incidence of leprosy disability, which may be related to differences in services between health regions and in the implementation of disease control interventions, particularly with regard to timely diagnosis and treatment. In addition, these findings highlight the importance of discussing the control of neglected diseases such as leprosy and the development of new technologies for their diagnosis and treatment. These initiatives are essential to improve the effectiveness of public health strategies to control this disease.