Stroke in Maputo Central Hospital, Mozambique 2019: A Glimpse of Epidemic or Endemicity?

Objective The aim of this study is to determine the endemic/epidemic pattern of stroke in Maputo Central Hospital in the first semester of 2019. Results During the period 2014-18, there were 2,979 registered cases of stroke in MCH, ranging from 512 in 2017 and 687 in 2015. The mean monthly registered cases per year ranged from 43 in 2017 to 57 in 2015. The C-SUM+1.96SD and mean+2SD methods have the highest monthly thresholds comparing to C-SUM and 3rd quartile methods. An epidemic pattern of stroke was observed during the first semester of 2019 when 3rd quartile and C-SUM threshold epidemic method was used. A relatively stable pattern of stroke occurrence with high registered cases was observed during the study period. It can be concluded that stroke is an endemic disease for the Maputo Central Hospital, with an epidemic pattern during the first semester of 2019. Adoption of 3rd quartile threshold methods for stroke surveillance might well add value for the control of the stroke epidemics.


Introduction
Stroke (cerebrovascular accident) is a noncommunicable disease (NCD) currently recognized as a major leading cause for reduced life expectancy at birth globally for men and women. According to World Health Organization, stroke mortality rates are higher in males, and the reduced life expectancy of males compared with that of females is not due to a single or a small number of causes [1]. The five main causes of death that contribute to a lower life expectancy in males than in females are ischemic heart disease, road injuries, lung cancers, chronic obstructive pulmonary disease and stroke [1].
Although not a communicable disease, the term "stroke epidemic" is being used widely in the literature [2 -6]. Two terms predominantly used for infectious diseases are herein important to recall: "epidemic" and "endemic". Epidemic is defined as the occurrence in a region or community of a number of excess cases, in relation to what would normally be expected; diseases are called endemic when in a geographical area or population group it presents a relatively stable pattern of occurrence with high incidence or prevalence [7].
Even if NCDs are non-infectious diseases, they may spread due to the social transmission of unhealthy activities such as unhealthy diet, physical inactivity, and smoking [8].
Therefore, stroke with his potential of social transmission of unfavorable social determinants of health, allowed us to borrow the "epidemic" and "endemic" terminology from infectious disease to describe certain occurrence and trends in a particularly geographical area.
The last published article on stroke in Mozambique is dated from 2010. The study shows crude and adjusted (world reference population) annual incidence rates of stroke of 148.7 per 100,000 and 260.1 per 100,000 aged 25 years, respectively-data from Maputo Central Hospital, 3 general public hospitals, the Military Hospital, and 6 private clinics [9].
Despite these rates, there is a gap of knowledge to determine if stroke is endemic or epidemic in Maputo Central Hospital.
The aim of this study is to determine the endemic/epidemic pattern of stroke in Maputo Central Hospital in the first semester of 2019.

Context
Maputo Central Hospital (MCH) is located in the city of Maputo (capital of Mozambique). Is a quaternary level hospital (the highest level in Mozambique) and is a national reference hospital. The direct catchment-population of the MCH is around 3 million inhabitants, and the indirect catchment-population is around 29 million inhabitants.
A cross-sectional hospital-based study was carried out in 2019, collecting secondary data (registered cases) from hospitalized patients with stroke from the years 2014-18, and first semester of 2019. All the Medicine wards (who admit stroke patients) from MCH were selected for the study data collection.
Building the endemic channel: Thresholds methods Four threshold epidemic detection methods were used, namely: i) monthly mean for the past five years plus two times the standard deviation (mean + 2SD); ii) cumulative sum method (C-SUM), which is the mean calculated over the combined previous, current and following months' data for the past five years; iii) C-SUM + 1.96SD; and iv) the 3rd quartile, which is the second highest value noted for the month over the past five years.

Description of the threshold methods
Mean + 2SD: uses the previous five years' data to construct an admissions profile for an average year at that location. The alert threshold for each month is then determined as the mean plus two times the standard deviation.
C-SUM: is based on the construction of an average or base year by calculating the expected number of cases using the average for that month (and the previous and following month) during the past five years.
C-SUM + 1.96SD: is based on C-SUM method refined by adding a 95% confidence interval. However, despite this increase, the awareness, treatment, and control among hypertensive patients remained extremely low, with 15%, 7%, and 3%, respectively [10].
The May Measurement Month initiative implemented in 2017 in Mozambique also revealed high proportion of hypertension (31.1%) among screened participants with very few in treatment and more than half of those in treatment were uncontrolled [11]. These low levels of awareness, treatment and control might be part of the triggers for an increase risk of stroke and the observed patterns in this study.

Increase in others modifiable risk factors
The increased prevalence and patterns of smoking habits (39.9% in men and 18.0% in women) [12], insufficient physical activity (6%) [13], Overweight and obesity (30.1% and 11.5% in urban areas, respectively) [14], alcohol use (57.7% in men and 28.9% in women) [15], among others modifiable risk factors in Mozambicans might additionally contribute for the occurrence of stroke events.

Better health services and access to MCH
The availability of Computerized Tomography Scan (since 2007) and Magnetic Resonance Imaging in MCH may have contributed to an improvement in the services provided for the diagnosis of stroke. Awareness that MCH have these technologies could have been exerted a confidence demand effect for first-care. Additionally, the improvement of the health information registration system can also contribute for the increase in registered cases, and the occurrence of the observed patterns. These factors cannot be discarded as contributing for the endemic and epidemic patterns observed in this analysis.

Reliability of the models
There is no threshold epidemic methods developed for NCDs, and therefore the authors used models tested for infectious disease (specifically malaria). Although this can be seen as a limitation, the available models for infectious disease can be temporarily used for surveillance purpose in the absence of more reliable and specific model for stroke and NCDs threshold detection. The 3 rd quartile threshold method showed more reliable for epidemic prediction when compared to the other methods. Therefore, the authors propose the use of this method for temporary surveillance of stroke in MCH.
Another limitation of this study is the fact that duplicates admissions raise problems in determining incidence rates. Despite these limitations, the study can be the first step to raise awareness for stroke surveillance in MCH, or even in Mozambique.

Declarations
List of abbreviations

Consent for publication
Not applicable.

Availability of data and materials
The datasets used and/or analysed during the current study are available from the corresponding author upon reasonable request.   Figure 1 Monthly thresholds of registered stroke cases with the four detection methods.

Figure 2
Monthly thresholds of registered stroke cases with the four detection methods and first semester 2019 registered stroke cases.

Supplementary Files
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