A Study on the Influence of an Outdoor Built Environment on the Activity Behavior of the Elderly in Small Cities in Cold Regions—A Case Study of Bei’an City

Under the dual constraints of limited resources and cold climate, the built environment of small cities in cold areas has a particularly prominent impact on the outdoor activities of the elderly and the need for aging optimization. Based on a questionnaire survey and field measurement data, combined with multiple linear regression, Spearman correlation analysis, and difference analysis, this paper systematically discusses the effects of different built environment characteristics on outdoor activity behaviors (frequency, intensity, and stay time) of the elderly in Bei’an City, Heilongjiang Province, China. The difference in environmental satisfaction of the elderly with different genders, ages, and education levels was analyzed. The results show that green coverage, air quality, leisure facilities, and barrier-free facilities are the core environmental factors that significantly improve the activity behavior of the elderly. In contrast, noise level, road damage, and inadequate facility maintenance significantly inhibit the activity willingness of the elderly. It was found that older adults are more dependent on barrier-free facilities and site safety, while younger people pay more attention to sports facilities and social space. Older women pay more attention to environmental details and cultural elements, while men tend to evaluate environmental functionality and so on. Further analysis shows that green environments and leisure facilities in cold climates provide visual beauty and play an important role in improving air quality and enhancing mental health. These elements are particularly critical in winter activities for older people, demonstrating the potential of the built environment to promote health and social participation. Starting from the unique background of small cities in cold regions, this study verified the applicability of the WHO age-friendly city framework in small cities in cold climates through empirical data, and revealed the necessity of climate-adaptive design (such as winter anti-slip facilities and cold-resistant greening) to improve the activity behavior of the elderly, providing a regional supplement to the existing theories.