[1] Univ Malaya, Fac Med, Dept Social & Prevent Med, Kuala Lumpur 50603, Malaysia
[2] Minist Hlth Malaysia, Seremban 70300, Malaysia
[3] Univ Malaya, Fac Med, Med Educ Res & Dev Unit, Kuala Lumpur 50603, Malaysia
[4] Taylorss Univ, Fac Hlth & Med Sci, Sch Med, Subang Jaya 47500, Malaysia