Measures

The SAS-SV contains 10 items, each scores on a Likert scale of 1 (strongly disagree) to 6 (strongly agree). The sum of these items gives an overall SAS-SV score (range: 10–60) with higher score indicating PSU. A native Chinese fluent in English translated the English SAS-SV into Chinese with local adaptations. We modified the 8th item of the original SAS-SV “Constantly checking my smartphone so as not to miss conversations between other people on Twitter or Facebook” by replacing “Twitter or Facebook” with “WhatsApp, Facebook, or WeChat,” which were more relevant to this study population. Backward translation was conducted by a native English speaker fluent in Chinese. Discrepancies were resolved by discussion and further modification before the instrument was finalized for use in this study.

Respondents reported their smoking status (categorized into “never smoker,” “former smoker,” and “current smoker”), alcohol drinking habit [“never drinker,” “former drinker,” “occasional drinker (<1 day/month),” “monthly drinker (1–3 days/month),” and “weekly to daily drinker (≥1 day/week)”], and number of days in the past week they performed at least 10 min of moderate physical exercise (recoded as “none,” “1–4 days,” and “5–7 days”). History of doctor-diagnosed chronic diseases was also reported (dichotomized as “yes” or “no”).

We also collected data on sex, age, and marital status (“unmarried,” “married/cohabitated,” “divorced/separated,” and “widowed”). Information on indicators of socioeconomic status (SES), including highest education level (“primary or below,” “secondary,” and “tertiary or above”), employment status (“employed,” “unemployed,” “homemakers,” “full-time students,” and “retired”), and monthly household income [“≥$40,000,” “$30,000–$39,999,” “$20,000–$29,999,” “$10,000–$19,999,” and “≤$9,999” (reported in HKD; HKD7.8 ≈ USD1)], was also collected.