[1] Univ Michigan, Dept Internal Med, Div Cardiovasc Med, Ann Arbor, MI 48106 USA
[2] Univ Milan, Fdn Policlin Mangiagalli Regina Elena, Ist Ricovero & Cura Carattere Sci, Dept Occupat & Environm Hlth, Milan, Italy
[3] Univ Milan, Fdn Policlin Mangiagalli Regina Elena, Ist Ricovero & Cura Carattere Sci, Inst Resp Dis, Milan, Italy