Travel patterns could be a confounding factor in the association between age and contact patterns in this study. Young adults may be more likely to travel than older adults, and travel could increase the opportunities for contact with others.
For example, young adults in Thailand may be more likely to take domestic or international trips for leisure, work, or study purposes. They may travel by plane, train, or bus, and stay in hotels or hostels where they may have more opportunities to interact with other travelers or local residents.
On the other hand, older adults may be less likely to travel or may take shorter trips closer to home. They may prefer to stay in more private accommodations such as vacation homes or relatives’ houses, where they may have fewer opportunities for contact with others.