Study population

This is a retrospective analysis of data collected from hospital EDs in three Polish cities–Olsztyn, Radom, and Wrocław covering the period 2016–2021. In total, 816 records in the healthcare system coded as I.47 according to the ICD 10 (PSVT) were analysed [2]. The majority of patients—54.66% (n = 446) seeking medical assistance due to PSVT were females (Table 1).

* numbers in brackets denote the percentage from a given column

To minimize the local character of the study, the occurrences of PSVT were analysed for divergent bioclimatic conditions in Poland, represented by EDs in three Polish cities located in different parts of the country (Fig 1). Olsztyn is a city with a population of about 180,000 inhabitants, situated in north-eastern Poland, Radom–has a population of about 210,000 and is in the south-eastern part of the country, and Wrocław–has about 643,000 inhabitants and is located in south-western Poland.

According to the Köppen climate classification, Poland is characterized by a cold climate without dry season and with warm summer (Dfb), (Fig 1A) [23]. Nevertheless, the variability of climatic conditions between the cities included in the retrospective analysis is noticeable. These differences concern the thermal conditions in particular. In the analysed period, the highest values of the annual average air temperature of 12.9°C were recorded in south-western Poland (Wrocław), whereas the lowest of 10.6°C in the north-east (Olsztyn). In Radom the values of this parameter were 11.4°C (Fig 1B). A similar differentiation level was noticeable for average monthly air temperature. Bioclimatic studies, considering the course of the heat balance of the human body, made it possible to distinguish several types of bioclimates in this relatively small country area (Fig 1B). The cities used for the analysis represent different types of Polish bioclimates according to the classification of Krawczyk B. [24]. Wrocław, with the highest mean air temperature in 2016–2021 among the studied cities, represents the region with low differentiation of thermal clothing insulation over the year, where moderate load of the thermoregulatory system due to respiration occurs (type 2.3). Radom represents the region with moderate differentiation of clothing thermal insulation, where a low load of the thermoregulatory system by respiration occurs (type 3.2). Olsztyn located in the coldest part of the country is characterized by moderate differentiation of thermal insulation of clothing with low or moderate load of the thermoregulatory system due to respiration (type 3.1 and 3.2). The inclusion of these cities to the study allowed for the highest possible, in Polish conditions, climatic differentiation, and, consequently, provided the basis for, at least partial, generalizations as regards the conclusions.

In each of the three cities there are a few hospital EDs that work in the 24/7 mode. We invited one ED from each city to participate in the study. In the analysed period (retrospective analysis) all three EDs, despite the COVID-19 pandemic, provided medical assistance irrespective of the cause of the problem. In the Polish healthcare system, EDs admit patients referred there by their general practitioners and by specialists who provide outpatients care, patients brought by ambulances, as well as those without any referral if their condition requires emergency care. The last group, by definition, embraces patients with symptomatic PSVT.