• green spaces

Takano and colleagues’ paper¹ on the association between proximity to “walkable green spaces” and longevity in senior citizens in Tokyo will be of interest to those involved in promoting health in its broadest sense. However, this study has a number of methodological limitations, the authors draw conclusions that are not supported by their results and the study does not merit the largely uncritical responses published elsewhere in the journal.^2–5

Only 3144 people of 7362 contacted (42.7%) agreed to take part in the survey. This response rate leads to the potential for substantial selection bias that is not discussed by the authors.

The questions used to determine proximity of participants to “walkable green spaces” are not explicitly described and their appropriateness cannot be determined. Asking if participants lived “near” to a place for taking a stroll will lead to highly subjective answers. In particular, those who do take strolls may be more likely to report proximity to such places merely because they are more aware of them. An objective measure of proximity to green spaces and a clear definition of what constitutes “green” would have significantly strengthened the study.

Takano et …