Authors’ contributions
Nina Tusa and Pekka Mäntyselkä contributed to the design of the study. Nina Tusa, Hannu Kautiainen, Pia Elfving, Sanna Sinikallio and Pekka Mäntyslekä contributed to the interpretation of the data. Nina Tusa, Hannu Kautiainen and Pekka Mäntyselkä contributed to the data collection and data analysis. The first draft of the manuscript was written by Nina Tusa and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.