A recent study revealed that an increase in midlife greenspace exposure may be equivalent to an 8-month delay in cognitive aging.
Published in Environmental Health Perspectives, researchers investigated the impact of midlife residential greenness on later-life cognitive decline among participants in the Nurses’ Health Study. The study analyzed data from 16,962 nurses who were enrolled in the substudy from 1995 to 2001 through 2008. Researchers utilized the Normalized Difference Vegetation Index to measure greenness within 270-meter and 1,230-meter buffers to assess both the immediate vicinity around residences and the larger walkable area as potential relevant geographic contexts, between 1986 and 1994.
From 1995 to 2001, participants aged ≥ 70 years with no history of stroke were invited to a telephone-based study of cognitive function. Among 22,715 eligible women, 92% participated in the initial cognitive interview, with follow-up assessments conducted at approximate 2-year intervals from 1995 to 2008, maintaining over 90% participation. The final sample included 16,962 women who had at least one cognitive assessment.
Cognitive function was assessed using validated telephone interviews, including the Telephone Interview of Cognitive Status and five other cognitive tests. Composite scores for global cognition and verbal memory were derived from z-scores of individual tests.
The study revealed that higher midlife greenness exposure was significantly associated with a slower annual rate of cognitive decline. Specifically, an interquartile range (IQR) increase in greenness (0.18) was linked to a 0.004-unit (95% confidence interval [CI], 0.001, 0.006) slower annual decline in global cognition—equivalent to an 8-month delay in cognitive aging. Among APOE-ɛ4 carriers—a known genetic risk factor for dementia—an IQR increase in greenness was associated with a 0.01-unit (95% CI, 0.0004, 0.02) slower rate of cognitive decline. No significant associations were found between greenness exposure and baseline or annual rate of cognitive decline in verbal memory.
Researchers noted midlife exposure to residential greenness also may provide cognitive benefits later in life for those with genetic predispositions to cognitive decline and those living in lower socioeconomic status neighborhoods.
“The latest report of the Lancet Commission on Dementia Prevention, Intervention, and Care observed that 40% of worldwide dementias could be prevented by addressing modifiable risk factors,” they stated, further cementing their findings on the benefit of greenspace exposure and the potential prevention of cognitive decline.
The authors reported no conflicts of interest.