How many candles on the cake this year?

Every year as we celebrate our birthdays, we mark the addition of a year to our lives. Our birthdays determine our chronological age measured in days, months and years since the day we were born. Biological aging on the other hand is another measure of aging that accounts for the gradual accumulation of cellular and tissue damage that occurs in the body as we grow older. Aging is a natural process and various factors contribute to biological aging, including our chronological age, genetics, lifestyle, nutrition, and physical activity. Research has shown poor nutrition and low physical activity can accelerate biological aging. Accelerated biological aging is marked by increased levels of certain hallmarks of cellular damage, leading to chronic diseases. Poor nutritional habits and sedentary lifestyles have been associated with increased risk of heart diseases, high blood pressure, cholesterol and type 2 diabetes. Additionally, over 60% of the aging population (>65 years) is expected to be affected by more than one chronic disease by 2030. Research has also shown that lifestyle interventions may reduce or delay the progress of biological aging. In this regard, Aline Thomas and colleagues obtained real life data from a large cohort of US adults to study the association between lifestyle behaviors and biological aging using mathematical models. They assessed signs of aging in individuals who engaged in some form of moderate to vigorous physical activity in their leisure time and followed a diet that resembled a mediterranean diet compared to individuals who followed a less-healthy lifestyle. A Mediterranean diet focuses on plant-based foods and healthy fats. It includes vegetables, fruits, whole grains, fish and extra virgin olive oil as a source of healthy fats. The researchers studied diet, exercise, and variations in healthy lifestyle behaviors across different age groups, genders, and body mass indices (BMI).

Dr. Thomas and colleagues combined data collected over a period of 20 years from 1999-2018 for their study. The study included 42,625 participants between the ages of 20-85 and assessed the adherence to the Mediterranean diet and an exercise regimen using a point based system. Inclusion of fruits and vegetables, legumes, cereals, fish and a ratio of mono-unsaturated to saturated fats were each awarded one point. A healthy Mediterranean diet also includes a mild-moderate amount of alcohol, which is 0-1 glass for women and 0-2 glasses for men. So, a point was given if a mild-moderate amount of alcohol was consumed. Dairy products and meat are not part of the Mediterranean diet. If participants had consumed these foods but had consumed it less than a specific amount, they were still awarded a point. The points were totaled and found to be between 0 and 9. Higher scores meant a higher adherence to the Mediterranean diet. Leisure time physical activity (LTPA) describes any physical activity performed during participants free disposable time. The researchers assessed LTPA based on the frequency, duration and intensity to calculate points / scores for each activity. They categorized the activity levels based on the scores per week into four groups ranging from – sedentary (0 points), low (<500 points), moderate (500-1000 points) and high (>1000 points). Biological age was calculated using an algorithm called PhenoAge. The algorithm calculates biological age based on chronological age and 8 biomarkers obtained from blood samples.

The study included individuals across different races, socio-economic backgrounds, marital statuses, income to poverty ratios, and with various lifestyle-related factors (e.g., smoking, BMI category, total energy intake), making it a representative population of US adults. The researchers found very interesting observations relating to diet and exercise. They discovered that adherence to a relatively healthy diet and engagement in  physical activity were independently associated with a lower biological age. Participants with a healthy diet and some level of activity were on average 1 biological year younger than the participants with the least healthy diet and sedentary lifestyle. Another very interesting finding was that individuals who had a less healthy diet but who were active even at a low level showed delayed biological aging. However, delayed biological aging was not found in participants with a healthy diet and a sedentary lifestyle, suggesting that moderate physical activity is a key component of healthy biological aging.

The findings of this study reiterates the need for better lifestyle choices across all strata of the population as the results were consistent regardless of age, sex and BMI category. A nutritious diet and moderately active lifestyle can have a positive impact on health, aging and quality of life. Getting older is inevitable, but you may be one year younger with a healthy diet and an exercise routine.

Reviewed by: Trang Nguyen, Giulia Mezzadri, Erin Cullen, Maaike Schilperoort 


The Importance of Consistent Sleep for Memory Retrieval at the Neural Level

Sleep helps us remember the details of past events more clearly. When we sleep, neural mechanisms facilitate the consolidation of memories formed during the waking day. Specifically, memories are temporarily stored in a brain structure called the hippocampus. During the consolidation process, memories are replayed and integrated into long-term storage centers in the neocortex of the brain. Poor sleep impairs sleep-based memory consolidation and memory retrieval. In other words, when our sleep is fragmented, our memory is less clear. 

One way to assess the clarity of a memory is to measure neural similarity, or the overlap between patterns of neural activity.  My colleagues and I presented participants with a series of word pairs to remember while we recorded their neural activity using electroencephalography. We used this task to measure neural activity when participants studied (i.e., encoded) and were tested on (i.e., retrieved) the word pairs. The overlap between their neural patterns for a given word pair at study and test is an index of neural similarity.

Interestingly, we found that sleep quality was associated with neural activity for word pairs that were paired differently. When people had more consistent sleep quality from night-to-night (measured with wrist-worn monitors), they had greater neural similarity when they correctly rejected word pairs that were paired differently. For example, if they saw the pair “wing – clock” during the study period and correctly identified “fork – clock” as a different pairing at test, they demonstrated higher neural similarity. 

There were several strengths of the study. We used an objective measure of sleep quality — wrist-worn monitors. We also measured sleep quality for seven nights, which allows for assessing night-to-night sleep variations. Our participants were racially and ethnically diverse people across the adult lifespan. However, our study was limited by its small, convenience-based sample of participants (74 people) and cross-sectional design. We cannot determine if poorer sleep causes lower neural similarity with this data. 

Taken together, our study suggests that memory integrity, or the ability to clearly remember the details of past events, may be linked with consistent sleep patterns. Thus, in addition to sleeping for enough time, sleep consistency also contributes to better memory retrieval. 

Edited by: Trang Nguyen, Pei-Yin Shih

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