The survey measures were translated into Mandarin, Malay and Tamil. To ensure the conceptual equivalence of the instruments in the different languages, the whole translation procedure followed a process that was adapted from guidelines of the World Health Organization, which had been used among two previous national studies in Singapore [22, 23]. This included 1) single forward translation by a professional firm; 2) review by an expert panel comprising the professional translators, content experts and a layperson to identify and resolve any inadequate expressions in the translation and discrepancies between the translated and original version; 3) pre-testing and cognitive interviews among individuals representing the target population in term of the age-groups, gender, ethnicities, and socio-demographics; and 4) development of the final version .