Assessing outdoor thermal comfort and activities of the elderly in urban parks: A case study in Xiamen, China

As the global population ages, the places where older adults spend their time are becoming a matter of urgent public health. For many seniors, the urban park is not just a scenic backdrop but a vital living room, a place for exercise, social connection, and mental well-being. Yet, the air itself can be a barrier. As people grow older, their bodies change; the internal systems that regulate temperature become less efficient, making them more vulnerable to both heat and cold. This vulnerability means that the simple act of sitting on a bench or walking a path depends heavily on the thermal environment. Researchers have long sought to define "thermal comfort"—the state where a person feels neither too hot nor too cold—but most of this work has focused on younger adults or specific, harsh climates. The question of how older people in warm, humid regions actually experience the outdoors has remained largely unanswered, leaving city planners without a clear guide for creating spaces that truly serve this growing demographic.

In the coastal city of Xiamen, China, a team of researchers set out to fill this gap by observing the daily lives of the elderly in four local parks. They spent a full year, from January to December, tracking the weather conditions and interviewing hundreds of seniors who were out enjoying the day. The team measured the air temperature, humidity, wind speed, and the intensity of sunlight hitting the ground. Crucially, they did not just look at the weather; they asked the people themselves how they felt. They recorded whether a senior felt cold, comfortable, or hot, and what they were doing at that moment. By combining these physical measurements with personal reports, the researchers could calculate a specific index known as the physiological equivalent temperature. This index translates complex weather data into a single number that represents how hot or cold the human body actually feels, accounting for the combined effects of sun, wind, and humidity.

The results revealed a nuanced picture of what the elderly in Xiamen need to feel comfortable. The study found that the "neutral" temperature—the point where an older person feels perfectly balanced—is 23.5 degrees Celsius. However, the range of temperatures they find acceptable is quite specific, stretching from about 19 degrees to 28 degrees. Interestingly, the seniors in the study consistently preferred a slightly warmer environment than the neutral point, with an ideal temperature of 25.5 degrees. This preference suggests that as people age, they may require a bit more warmth to feel satisfied, likely because their bodies generate less heat and are less prone to perceive heat. The researchers also determined that when the temperature felt equivalent to 37 degrees Celsius or higher, park attendance dropped dramatically, with very few seniors willing to be outdoors.

Beyond simple temperature, the study identified what drives these feelings. The physical environment, particularly the heat radiating from the ground and the air temperature, was the most powerful factor influencing how comfortable a person felt. While psychological factors like how long someone had lived in the city or their general satisfaction with life played a role, and social factors like being with a companion offered some comfort, these were secondary to the actual weather conditions. The data showed that physical factors were the primary drivers of thermal sensation, followed by individual characteristics like age and how much clothing a person wore. The presence of a companion did help; seniors who were with others reported feeling more comfortable and were more tolerant of less-than-ideal weather, suggesting that social connection can buffer against physical discomfort.

The relationship between the weather and how many people showed up to the park changed with the seasons. In the spring and autumn, attendance followed a curved pattern: as the temperature rose toward the comfortable range, more people came out, but once it got too warm, the numbers fell. In the summer, the relationship was a straight line downward; as the heat intensified, fewer and fewer seniors ventured out, and when the heat index exceeded 37 degrees, the parks were nearly empty. To cope with the heat, the elderly relied heavily on their surroundings. When it was too hot, they moved into the shade. When it was too cold, they sought out the sun. They also adjusted their behavior by drinking water or changing their activity levels, such as walking more vigorously in the winter to generate body heat. These findings paint a clear picture of how older adults actively manage their environment to stay comfortable.

The study concludes that designing age-friendly parks requires more than just planting trees; it demands a precise understanding of thermal thresholds. The data suggests that to keep older adults active and engaged, urban spaces must offer a variety of microclimates, from sunny spots for winter warmth to deep shade for summer relief. By designing parks that respect the specific thermal needs of the elderly—providing shelter from extreme heat and access to sunlight in cooler months—cities can encourage seniors to remain active outdoors. This is not just about comfort; it is about health. When the environment is right, the elderly are more likely to leave their homes, socialize, and exercise, contributing to a healthier, more vibrant aging population. The research provides a concrete foundation for architects and planners to build spaces that are not just accessible, but truly welcoming to the growing number of older citizens.