[1] Univ Med & Dent New Jersey, Robert Wood Johnson Med Sch, Dept Family Med, New Brunswick, NJ 08903 USA
[2] Lehigh Valley Hosp, Dept Family Med, Allentown, PA USA
[3] Case Western Reserve Univ, Dept Family Med, Cleveland, OH 44106 USA
[4] Univ Hosp Cleveland, Dept Epidemiol & Biostat, Cleveland, OH 44106 USA
[5] Univ Hosp Cleveland, Dept Sociol, Cleveland, OH 44106 USA