The pandemic response led to "sustained cognitive decline" among the over-50s, particularly but not exclusively among those who already had mild cognitive impairment (MCI), according to research led by the University of Exeter, which found the deterioration occurred in those with and without a history of COVID-19.
Although they were not able to prove cause and effect, the researchers speculated that reductions in social contact, physical exercise, and cognitive stimulation during pandemic restrictions may have been a contributory factor.
Moreover, declines continued into the second year of the pandemic, suggesting an impact beyond the initial 12-month period of lockdowns.
Lockdown Restrictions Potentially Detrimental to Cognitive Health
The authors predicted that the measures enacted during the pandemic would "hold the potential for considerable detriment to cognitive and mental health, particularly because major dementia risk factors — such as those related to exercise and dietary habits — were affected during this period".
The study, published in The Lancet Healthy Longevity, used longitudinal data from the ongoing PROTECT study to evaluate the effect of the pandemic on cognition among older adults in the UK. The remote online study, run by the University of Exeter and King's College London, aims to understand how healthy brains age and why people develop dementia.
For the current study, researchers assessed data from computerised neuropsychology tests on a sample of 3142 UK participants (mean age 67.5 years, 54% women) with no dementia diagnosis at baseline.
Data had been collected from the same participants for the year prior to the pandemic (1 March, 2019–29 February, 2020), in the first year, which included three lockdowns (1 March 2020–28 February, 2021), and in the second year (1 March 2021–28 February, 2022) when restrictions were eased.
Significant Worsening of Executive Function and Working Memory
Analysis of the data showed significant worsening of executive function and working memory during the first year of the pandemic (effect size 0.15 [95% confidence interval, 0.12–0.17] for executive function and 0.51 [0.49–0.53] for working memory). The decline was evident in both subgroups of those with MCI (0.13 [0.07–0.20] and 0.40 [0.36–0.47]) and with COVID (0.24 [0.16–0.31] and 0.46 [0.39–0.53]).
The authors said that the scale of change was noteworthy, with all groups — the whole cohort and the individual subgroups — showing more than a 50% greater decline in working memory and executive function. This effect was sustained for working memory into the second year of the pandemic, with a continuation of accelerated decline relative to prepandemic levels (0.47; 0.44–0.49).
Dementia Risk Factors Exacerbated by Lockdowns
The researchers also extracted data on lifestyle influences with the most robust connections to well-established dementia risk factors. Regression analysis showed that cognitive decline was significantly associated with a decrease in physical activity and increased alcohol use across the overall cohort and in the MCI and COVID subgroups.
In people with MCI, loneliness and depression were specifically associated with cognitive decline, while for people with a history of COVID, cognitive decline was associated with depression. In the second year of the pandemic, decreased frequency of physical activity was the only factor that continued to affect executive function across the whole cohort.
However, in people with MCI, increased alcohol use, loneliness, and depression continued to be associated with worsening working memory. In people with a history of COVID-19, associations were still evident between working memory and decreased frequency of exercise, loneliness, and depression.
Ongoing Effects "Yet to be Fully Established"
The researchers commented that the strict social restrictions imposed during the pandemic, including physical distancing, quarantine, and full societal lockdowns, "had not previously been experienced in living memory", and their ongoing effects "are yet to be fully established". However, the neuropsychological consequences "have particular relevance for older adults in the context of increased potential dementia risk".
The restrictions "accelerated cognitive decline" in individuals with MCI, the researchers said, and "a key emerging question is whether their risk of conversion to dementia has also increased".
The authors concluded: "The sustained decline in cognition highlights the need for public health interventions to mitigate the risk of dementia – particularly in people with MCI, in whom conversion to dementia within 5 years is a substantial risk."
Their study echoes previous research from France, Japan, and China, showing that social isolation in the pandemic accelerated cognitive decline among older adults.
First author and PROTECT study lead Anne Corbett, professor of dementia research at the University of Exeter, said: "Our findings suggest that lockdowns and other restrictions we experienced during the pandemic have had a real lasting impact on brain health in people aged 50 or over, even after the lockdowns ended. This raises the important question of whether people are at a potentially higher risk of cognitive decline, which can lead to dementia."
She added: "Our findings also highlight the need for policymakers to consider the wider health impacts of restrictions like lockdowns when planning for a future pandemic response."
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