Funding for this research was provided by:
Social Insurance Institution of Finland
Text and Data Mining valid from 2018-06-05
Received: 26 January 2016
Accepted: 15 May 2018
First Online: 5 June 2018
Ethics approval and consent to participate
: Ethics approval was granted by the Ethical Committee of the Hjelt Institute, University of Helsinki. The Ethical Committee also approved the consent procedure. An information letter describing the purpose of the study was sent together with the questionnaire to the respondents by the SII. The letter also stated that participation in the study, i.e. completion of the questionnaire, was voluntary. Consent to participate in this mailed questionnaire study was given by the act of returning the questionnaire.
: The authors declare that they have no competing interests.
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