Moderate Physical Activity May Improve Overnight Memory Retention in Older Adults

Moderate-intensity physical activity is associated with better emotional memory consolidation among older adults, according to study results published in Scientific Reports. 

The ability to recall emotionally rich memories may have a positive impact on quality of life among older adults. However, previous research has demonstrated that the aging process may negatively affect sleep, which plays a critical role in the consolidation of memories.

In this study, researchers aimed to understand the relationship between physical activity (PA) and sleep-related consolidation of emotional memory among older adults. Eligible older adults were enrolled in the clinical trial and assessed with an overnight sleep study and an emotional memory test before and after sleep. The researchers categorized participants’ physical activities into 4 groups based on a self-reported questionnaire assessment: sedentary activity, non-exertive activity, light-intensity physical activity, and moderate-intensity physical activity.

A total of 40 cognitively healthy older adults were included in the study, 65% of whom were women and 65% were more than 1 race. Participants had a mean age of 72.3 (SD=5.8) years, body mass index (BMI) of 24.7 (SD=5.6) kg/m², and apnea-hypopnea index (AHI) of 13.4 (SD=17.4) events/h. Overall, 80% of participants met guidelines for moderate-intensity physical activity (MPA), with at least 150 min/wk.

To analyze the results, the researchers used a multiple regression model that adjusted for age, sex, and AHI. False Discovery Rate (FDR) correction was used to adjust for multiple comparisons.

The researchers did not observe a statistically significant relationship between MPA frequency and overnight retention of emotional mnemonic discrimination. Mnemonic discrimination measures the quality of memory representations or how well the brain separates the storage of similar experiences into unique ones.

However, MPA frequency (B=0.663; SE=0.212; P =.009) was associated with better overnight retention of negative emotional recognition memory — but not positive or neutral recognition memory. The researchers also found that MPA duration (B=0.214; SE=0.101; P =.042) was also linked to better overnight retention of negative recognition memory, but this relationship did not remain significant after FDR correction. When sleep duration was added as an additional covariate, MPA frequency remained significantly associated with negative emotional memory consolidation (B=0.666; SE=0.221; P =.005), but MPA duration only trended toward significance (B=0.210; SE=0.106; P =.0555).

The researchers further evaluated whether MPA was associated specifically with memory consolidation or whether these findings were driven by memory performance prior to sleep. They found that MPA was not associated with immediate performance before sleep, but that MPA frequency (B=0.421; SE=0.230; P =.076) and MPA duration (B=0.815; SE=0.103; P =.082) trended toward significance on the negative emotional memory test after sleep. These findings suggest that exercise helps drive consolidation-specific processes among older adults. Additionally, when sleep duration was included as a covariate, the results were similar for MPA frequency (B=0.441; SE=0.240; P =.075) and MPA duration (B=0.195; SE=0.108; P =.081).

The investigators also used Isotemporal Substitution Modelling (ISM) to theoretically reallocate 30 minutes of non-exertive activity or light-intensity physical activity to MPA, which showed a statistically significant relationship (B=0.108; SE=0.048; P =.030) and a trending relationship (B=0.100; SE=0.059; P =.099) with better overnight negative memory retention, respectively.

Light-intensity and non-exertive physical activity were not significantly associated with memory consolidation in any models.

The study authors concluded, “Results from the current study suggest that higher engagement in MPA (both frequency and duration) supports sleep-related negative emotional memory consolidation in older adults.” They added, “The study found that PA was specifically associated with negative recognition memory but not negative mnemonic discrimination ability.”

Study limitations include potentially inaccurate baseline fitness levels from self-reported physical activity assessments and lack of generalizability due to the small sample size of moderately active participants with sleep-disordered breathing (SDB) and unreported severity of cognitive impairment.

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of author disclosures.

This article originally appeared on Sleep Wake Advisor