[1] Norrbotten Cty Council, OLIN Studies, Lulea, Sweden
[2] Umea Univ, Dept Publ Hlth & Clin Med Occupat & Environm Med, Lulea, Sweden
[3] Lulea Univ Technol, Div Nursing, Dept Hlth Sci, Lulea, Sweden
[4] Umea Univ, Div Resp Med, Dept Publ Hlth & Clin Med, Umea, Sweden