SIR—Older people with mobility limitations often report more barriers in their outdoor environment than people with intact mobility [1]. However, it is uncertain whether older people perceive their environment as problematic because of their mobility limitations or whether the environmental barriers precede incident mobility limitation, as most studies have been limited to cross-sectional analyses [2–5]. Only a few longitudinal studies have shown that barriers in the outdoor environment, such as poor street conditions, poor lighting and heavy traffic, increase the risk for overall functional loss [6, 7] and decrease physical activity participation [8]. More knowledge is needed about the characteristics of outdoor environments that threaten the mobility of older people [9].

The aim of the study reported in this letter was to explore whether perceived barriers in the outdoor environment predict development of difficulties in advanced and basic mobility among community-dwelling people who did not have walking difficulties at baseline.