Seasons have a significant impact on cognition in older adults, including those with Alzheimer’s Disease (AD), with a measurable drop in mental ability evident during the northern hemisphere winter.1 This effect was consistent across three observational community-based cohorts (which together included more than three thousand people) and independent of confounding variables such as depression and sleep disturbance.
Winter is significantly associated with impaired cognition and low CSF Aβ 42
Season affects cognition, biomarkers and gene expression
- On a battery of 19 tests, the overall seasonal difference was equivalent to 4.8 years of normal cognitive decline and likely to be significant for both diagnosis and management. In winter and spring, the odds ratio of meeting the criteria for mild cognitive impairment or dementia was 1.31
- In the subgroup of people who had lumbar puncture, levels of CSF amyloidβ-42 were lowest in the winter.
- Among people who were autopsied, gene expression assessed by RNA sequencing in the dorsolateral prefrontal cortex – a key node for working memory – also showed a seasonal rhythm, and this correlated with changes in cognition.
Non-motor PD symptoms worsen in winter
Scores on the Parkinson’s disease non-motor symptom scale show greater disability in winter, according to data from 372 consecutive PD patients.2 The difference is large enough to influence care needs and medication.
The investigators attribute the seasonal variation to altered functioning in the body's master clock, the suprachiasmatic nuclei. Among domains significantly affected are cardiovascular symptoms and perception.
Although problems can occur in summer, vasomotor-related symptoms of cold in the distal limbs – reported by up to 50% of people with PD – are typically associated with winter.3 Cold sensitivity is linked to pain and can be physically disabling.
Social factors can also cause distress
With the associated festivities, midwinter is generally a time of cultural as well as climatic challenge for people with neurodegenerative conditions. Covid-19 has made 2020 exceptional, but the challenges persist.
The season creates opportunities to evoke treasured memories, but also possible distress when circumstances contrast so starkly with the past.
For those in institutions, midwinter brings disruption, with confusing changes in staff and routine. For all, longer hours of darkness make it difficult to distinguish between night and day.
Among potentially helpful suggestions for people with dementia:4
- Keep to routine if possible and plan for changes
- Ensure supply of medications
- Have a quiet area available
- Evoke memories but don’t follow traditions that are no longer appropriate
- In relation to food, keep the person involved in cooking if they wish. Don’t worry about timings and don’t put too much on the plate of someone with reduced appetite
- If someone does not feel festive, don’t force it on them.
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