If you're worried about dementia or a more subtle loss of intellectual capacity as you age, there are plenty of suggestions on what to do. Although everything from diet to improved greater intellectual activity is thought to help, you may not have considered the influence of where you live. However, it appears that being surrounded by greenery makes a difference.
The Whitehall II study tracked 10,000 British civil servants' health over many years. Using a sample of 6,506 aged between 45 and 68, Carmen de Keijzer, a PhD student at the Barcelona Institute for Global Health, compared how verbal and mathematical reasoning, short-term memory, and eloquence changed over a period of 10 years.
"Our data show that the decline in the cognitive score after the 10-years follow up was 4.6% smaller in participants living in greener neighborhoods," de Keijzer said in a statement. "Interestingly enough, the observed associations were stronger among women, which makes us think that these relations might be modified by gender."
The difference may seem small, but considering the immense cost to society and the loss of quality of life associated with declines in these areas, even a small difference could have enormous consequences. Moreover, if future research can establish what it is about leafy environments that provide these benefits, we might be able to make even bigger differences.
The conclusions, published in Environmental Health Perspectives, are drawn by comparing the amount of green space within 500 meters (1,600 feet) and 1,000 meters (3,300 feet) around participants' homes.
Wealthier areas usually have more parks, or at least larger gardens, but de Kejzer's figures controlled for the effects of income, as well as age, marital status, type of job, diet, and alcohol and cigarette use.
This leaves at least two explanations for the effect. On the one hand, there is a wealth of evidence for the psychological and physical benefits of access to nature. It's plausible the happiness that comes with being surrounded by grass and trees, or an increased propensity to go for walks outside, provide a buffer against cognitive decline.
Alternatively, de Keijzer noted: “There is evidence that the risk for dementia and cognitive decline can be affected by exposure to urban-related environmental hazards (such as air pollution and noise).” Trees, and to a lesser extent grassy areas, reduce both of these, so the effect de Keijzer found is hardly a surprise.
Indeed, previous studies have found children's cognitive capacities benefit from growing up around green space.
Nevertheless, the relationship between green space and intellectual capacity among older people has not previously been explored over the long-term. It's unlikely many urban planners include this as one of the benefits of adding more parks to urban areas, but maybe they should.