**Ethical approval (human)**

The Ethical Committee consent for the presented research is not required. According to the statement of the Ethical Committee of the Medical University of Warsaw: "The Committee does not provide opinions on surveys, retrospective studies, or other non-invasive research" (Detailed information and templates of documents of Ethics Committee of Medical University of Warsaw (Accessed 2016-10-01): http://komisjabioetyczna.wum.edu.pl/content/ szczeg%C3%B3%C5%82owe-informacje-orazwzory-dokument%C3%B3w).
