Table 1.

Summary of Studies Reviewed

Outcome	Study Designs	Setting	Findings	Strength of Evidence
Physical Activity	3 longitudinal studies[19,30,33] 3 surveys [9,36,37]	2 in Canada, 1 each in USA, Germany, Belgium	There was previously consistent associations between greenness and increased physical activity but few prospective studies. Presently, 3 accelerometry and 2 survey-based studies found positive associations between greenness and physical activity. The odds of using active transportation to commute was higher among those with higher NDVI at the residence, destination, and along the path of the commute.	High
Mental Health	5 cross sectional studies [16,18,22,27,28] 2 longitudinal surveys [29,34] 2 prospective cohort [8,39]	3 in Spain, 1 each in USA, Canada, Korea, United Kingdom, Sweden, 1 combining Spain, Netherlands, Lithuania, and United Kingdom	Previous review found that mental health studies found some evidence of positive associations with self-rated health but was lacking in prospective studies. Current review found associations with lower risk of depression and depression symptoms using some greenness measures but not others. This occurred in some studies of self-rated general health as the outcome. There was limited evidence for a link between greenness and cognitive function. Among children, there was one prospective study showing association with improved cognitive ability.	Intermediate
Birth Outcomes	6 birth cohort studies [10–13,25,35] 1 prospective cohort [20]	5 in USA, 1 each in Belgium, Lithuania	Previously, we found consistent evidence for associations between greenness and higher birth weight. Current review expands on this and found associations with lower risk of preterm birth, low birth weight, and small for gestational age. There may be effect modification by socioeconomic status as well as geographic location.	High
Asthma and Allergy	2 prospective cohorts [26,45] 1 case control [14] 1 ecological study [67]	1 from each of Lithuania, Crete, and Spain, 1 combining data from Sweden, Australia, Canada, and Germany	Prior review did not find consistent evidence for associations between greenness and outcomes related to asthma and allergy. In the present review, we found that pooled data from multiple cohorts resulted in no significant associations between greenness and allergy-related symptoms such as bronchitis, wheezing, asthma, and allergic rhinitis. One study, using data from one city, found a positive association with asthma diagnosis. Overall, there are geographic variations in associations between greenness and asthma and allergy related symptoms. In an ecological study, NDVI predicted number of allergic reaction admissions at hospitals with high accuracy.	Low
Cardiovascular Outcomes	3 prospective cohorts [15,30,50]	1 each in Belgium, Germany, Israel	We previously found ecological and cross sectional studies showing associations with lower cardiovascular disease risk. With the prospective studies in the current review, an association was found between greenness and lower night systolic blood pressure. However, there was no consistent pattern of associations found for blood lipids such as cholesterol, high/low density lipoprotein, and triglycerides.	Low to intermediate
Mortality	3 prospective cohorts [23,51,52] 3 ecological studies [53–55]	1 in each of USA, Canada, Spain, Portugal, Switzerland, Korea	Previous review included mostly ecological studies and only cohorts of subgroups of the population. The current review found three large, national cohort studies that demonstrated a strong protective effect of greenness on all-cause mortality and mortality from respiratory and cardiovascular diseases. There was some evidence that SES modifies this relationship in two cohort studies and one ecological study. Two ecologic studies show that greenness modifies the relationship between extreme heat and mortality: lower risks of death among areas with higher greenness.	High
Other	Cross sectional study [9,56,68] Case control [17] Case crossover [60] Ecological Study[24,57,59] Longitudinal survey [32]	2 in each of Germany and USA, 1 each in Canada, United Kingdom, Spain, Uganda	Increases in greenness were associated with: lower insulin resistance, lower obesity metrics, lower odds of prostate cancer, lower malaria-related parasites, and higher self-rated general health. Among children and adolescents, greenness was associated with lower rates of spectacle use, school absenteeism, autism, and gun assaults.	N/A

Strength of evidence definitions:

High: evidence is consistent, plausible, and precisely quantified and there is low probability of bias

Intermediate: evidence exists, but not entirely consistent, is not quantified precisely, or may be vulnerable to bias

Low: evidence is inconsistent, implausible, and/or may be vulnerable to bias severely limiting the value of the effect being described