Urban Green Space Visits and Mortality Among Older Adults.

Abstract

To the Editor: Time spent in nature and green spaces has positive physical and mental health effects.1–4 Studies have found quality and quantity of urban green spaces to be mildly associated with mortality and life expectancy, but there are few studies addressing the question.5–8 Whether frequency of urban green space visits have an impact on mortality among older people has not been previously studied. To our knowledge, the present study is the first to examine this issue. We conducted a 3-year prospective study using data from the Seniors in the City Project (2008–2010) at the Age Institute in Finland. The study was approved by the ethical board of the Age Institute. We used a cross-sectional survey from 2008 to study all home-dwelling older adults aged 75 and over living in one of the central areas of the city centre of Helsinki, the capital of Finland. In the area or nearby, there are 14 such green spaces that could be considered areas where people spend time. These green spaces are city parks, including one cemetery and one botanical garden. The average distance from older people’s homes to these green spaces is 230 m (median: 200 m). The total sample size at the baseline was 1,968 people, of whom 1,395 answered the survey (456 men and 939 women aged 75–99 years, response rate 71%). The mean age for men was 81 and for women 82. After 3 years of the survey, information on all-cause mortality was linked to this survey from the National Population Information System. Among those people who answered the survey, 204 had died in 3 years (86 men and 118 women). Mortality rate for men was 19% and for women 13%. We divided the variable of visiting urban green spaces in the year 2008 into the four categories shown in the Table. These categories were designed to include a reasonable number of respondents in each category. Other variables are introduced in the footnotes of the Table. First, we assessed the prevalence of all-cause mortality in terms of urban green space visits (using IBM SPSS 22 software). We then used a Cox proportional hazards model to examine whether urban green space visits predicted mortality risk.TABLE: Hazard Ratio with 95% Confidence Intervals for Mortality by Urban Green Space VisitsThe all-cause mortality rate for older people visiting urban green spaces daily was 7%. Those who visited 2 to 6 times per week had a mortality rate of 12%. Corresponding figure for those who visited these spaces 2–4 times per month was 11% and 24% for those who visited few times a year or less (not tabulated). Unadjusted figures in the table show that older adults who visited green spaces a few times a year or fewer had higher risk of all-cause mortality, hazard ratio (95% confidence interval) of 3.9 (2.3, 6.4), compared with those who visited green spaces daily. Adjusting for sociodemographic variables (model 1) and further diseases (model 2) attenuated this risk slightly. After adjusting for functional capacity in model 3, all-cause mortality in those older adults visiting green spaces infrequently was greater, hazard ratio (95% confidence interval) of 2.2 (1.2, 4.1), in comparison to those who visited these spaces daily. In conclusion, those who visit urban green spaces most infrequently had the highest risk of mortality. Results are partly in line with the earlier studies.5–8 Strengths of this study are the high response rate and statistical control of comorbidities and functional capacity. However, the point estimates of green space visits are fairly imprecise and there is no exact information on whether “spend time” means sitting or walking. Furthermore, changes in urban green space visits between baseline and 3 years of follow-up would be interesting, as would information on whether urban green space visits predict quality of life and functional independence. Even though there are other factors, such as lifestyle, which could have impact on our result, diseases and functional capacity are such strong predictors of mortality that controlling for them in the present analyses raises the question: is there a true independent effect of urban green space visits on mortality? Tommi Sulander Department of Forest Sciences University of Helsinki Helsinki, Finland [email protected] Elina Karvinen The Age Institute Helsinki, Finland Markus Holopainen Department of Forest Sciences University of Helsinki Helsinki, Finland