The Effect of Mid-Life Diet on Cognitive Complaints in Women

October 31, 2023 by Leigh Christopher

The takeaway

There is limited evidence on how diet, a factor influencing health conditions like hypertension and diabetes, impacts cognition in women in later life. Researchers found that adherence to a DASH (Dietary Approaches to Stop Hypertension) diet in mid-life led to a lower prevalence of cognitive complaints (SCC) in late life, specifically in women.

What's the science?

Alzheimer’s Disease (AD) is the most common form of dementia and affects approximately 6.5 million people in the United States, and almost two-thirds of AD cases are women. Subjective cognitive concerns or SCCs are self-reported impairments in daily cognitive performance and have been increasingly reported to be associated with incident neurocognitive disorders such as AD. However, there is limited research on how dietary patterns — a potential modifiable risk factor — could influence these cognitive complaints. The DASH diet has been highly researched within the context of maintaining a healthy hypertension and cardiovascular profile but its role in preserving optimal cognitive function in later life is not known. This week in Alzheimer’s & Dementia, Dr. Song and colleagues at New York University (NYU) Grossman School of Medicine used population genetics and epidemiology-based approaches to understand the impact of a DASH diet on SCCs in over 5,000 women from the New York University Women’s Health Study (NYUWHS).

How did they do it?

The researchers included 5116 women participants aged 35 to 65 from the NYUWHS study. Participants were followed for up to 5 years and each completed a questionnaire giving information about their regular diet, intensity of physical activity, etc. as well as a formal SCC survey at different time points during the study. The assessment of DASH diet and quantification of DASH scores were based on predefined metrics - a high intake of fruits, vegetables, legumes and nuts, low-fat dairy, and grains were all indicative of greater adherence to the DASH diet and the highest quintiles were thus given the highest score ( = 5). The total DASH score was determined by adding the scores of the eight DASH components (different food groups such as fruits, vegetables, whole grains, dairy, sodium, processed meat, sweetened beverages), resulting in a potential range of 8 to 40, with higher DASH scores reflecting greater adherence to the diet. The authors conducted statistical analyses including a) stratification of participants by factors including age, total calories, BMI, education and race, with multiplicative interaction to assess the effects of these factors, and b) multiple longitudinal regression models with appropriate covariates such as education, health history, etc. and were used to assess the continuous relationship between SCC and DASH scores (cumulative and also separately for all eight components individually) for all the women in the study.

What did they find?

The researchers found that greater adherence to DASH diet in mid-life was associated with 20% lower odds of having higher subjective cognitive complaints (SCC greater than or equal to 2 in the SCC scale). Upon stratification, they also found that this association was stronger amongst Black women and amongst those without a history of cancer. These associations remained after adjusting for potential confounding variables and considering missing data points. Using linear regression analysis, the researchers confirmed that a higher DASH score was associated with a lower number of SCCs later in life. They even found that individual components of the DASH diet (consumption of fruit, vegetables, legumes, nuts, etc.) were associated with lower incidences and severity of later-life subjective cognitive decline, although after accounting for all other individual components, only fruit consumption remained significant.

What's the impact?

This study shows that greater adherence to a DASH diet in mid-life could be therapeutic in preserving cognition in later life in women. Overall, this study suggests the immense potential of diet quality, especially the diet related to hypertension and cardiovascular profile in maintaining healthy cognitive function

Access the original scientific publication here.

The Role of Circadian Rhythm in Mood Disorders

October 31, 2023 by Leigh Christopher

Post by Rebecca Hill

How does the circadian rhythm impact mood?

Circadian rhythms are physiological mechanisms that allow humans and many other animals to respond to light and have regular periods of both activity and restful sleep. Circadian rhythms are coordinated by an area in the hypothalamus called the suprachiasmatic nucleus (SCN), which receives direct light input from the retina (Reppert & Weaver, 2001). There is now a growing body of evidence that mood disorders, often diagnosed by abnormal sleep patterns, are associated with disrupted circadian rhythms. These studies have contributed to our understanding of mood disorders and how they can be treated, showing that therapeutic treatments that target circadian mechanisms can often help lessen the symptoms of mood disorders.

Some of the most common mood disorders include seasonal affective disorder (SAD), major depressive disorder (MDD), and bipolar disorder (BD), with each affecting between 2.8-5% of adults. A core diagnostic symptom of all mood disorders is abnormal sleep/wake patterns. Symptoms for SAD usually start during the change from fall to winter when the daylight hours quickly become shorter (Melrose, 2015). Similarly, manic and depressive episodes of BD are often triggered by seasonal changes (Geoffroy et al., 2014). Patients with BD usually have their sleep/wake patterns disrupted by manic and depressive episodes, which are also in turn triggered by changes to sleep patterns (McCarthy et al., 2022; Malkoff-Schwartz et al., 2000). In MDD, patients cycle through depressive moods throughout the day, with the worst symptoms usually occurring in the early morning (Wirz-Justice, 2022).

The prevalence of depressive mood disorders is increasing, and this could be linked to disrupted sleep driven by the uptick in the amounts of artificial light we are exposed to from phones, computers, and televisions, especially at night (Hidaka, 2012). In addition to this, shift work is common, and forces workers to be awake when their bodies expect to be asleep. This disrupts natural circadian rhythms and may also contribute to the increasing prevalence of mood disorder diagnoses (Boivin et al., 2022).

Neurons signal to adapt to changes in daylight

Midbrain dopamine neurons have been found to be linked to symptoms of depression. Rats exposed to short light days had more dopamine neurons in the hypothalamus that, when damaged, started presenting depression-like behavior (Dulcis et al., 2013). The neurons in the SCN signal at different rates during the summer and winter months, so individuals with SAD may have a SCN that can’t adapt to different seasonal cues (VanderLeest et al., 2007). Manic-like behavior, like that seen in patients with BD, was found in mice with optogenetic stimulation of dopamine neurons, but only at certain times of the day (Sidor et al., 2015). Together, research findings like these indicate that neurons are signaling changes in daylight throughout the seasons, and abnormal signaling could result in the symptoms seen in mood disorders.

Melatonin dysfunction contributes to mood disorders

Melatonin is a hormone released by the pineal gland to indicate darkness and facilitate sleep, meaning more melatonin is released during shorter days. Patients with SAD sometimes have an overproduction of melatonin during the winter and also produce it later in the day than normal, leading to fatigue during the daytime (Lewy et al., 2006; Srinivasan et al., 2006). Melatonin is also produced less, and at inappropriate times of the day by patients with MDD (Pandi-Perumal et al., 2020). Further, individuals with BD are hypersensitive to light at night, which can lead to the suppression of melatonin, and a delay in sleep.

How can we treat these mood disorder symptoms?

Bright-light therapy is the most widely used treatment for SAD. This treatment is typically used in the early morning, since this is the most effective timing window, however, the optimal timing and “dose” of light can vary for each person (Partonen, 1994). Bright-light therapy might work, especially if used in the morning, because it decreases the amount of melatonin being produced at inappropriate times during the day (West et al., 2011), and gives our bodies a strong morning light cue.

Antidepressant medications such as selective serotonin reuptake inhibitors (SSRIs) have also shown promise in helping to reset signaling in the SCN to correct circadian rhythms and decrease depression symptoms (Sprouse et al., 2006). Patients with BD are often treated with lithium, which when used in subjects with shorter circadian periods will lengthen the circadian period, correcting it to the natural 24-hour cycle (Mishra et al., 2021).

What’s next?

For proper mood regulation, the physiological circadian systems must be able to adapt to changes in daylight across the seasons. Individuals with an unstable sleep/wake cycle are more likely to develop mood disorders. Based on recent research, the stabilization of circadian rhythms can often treat the symptoms of mood disorders. Treatments such as bright-light therapy, melatonin, and SSRIs, when personalized to the individual, can greatly improve the outlook for patients with depressive mood disorders.

References +

Music-Induced Emotions Affect How We Encode Memories

October 24, 2023 by Leigh Christopher

Post by Anastasia Sares

The takeaway

Emotion and memory are tightly linked, but it is hard to measure continuous fluctuations in emotional states reliably in the lab. This work used music to reliably induce emotions across time and examined how transitions between different emotional states affect memory.

What's the science?

We are constantly processing the continuous stream of experience that happens in life, placing similar information into different “episodes” so that we can store them efficiently in memory. Transitioning into new contexts or situations can lead to uncertainty, like walking out of a building or changing conversation partners at a party, for example. Therefore, we are generally more vigilant during these times, paying more attention to what is new and having better memory for individual items. On the other hand, within an episode, we are better at remembering relationships between different items and the order of information, such as the numbers of the rooms we pass in a hallway or the order of topics in a conversation.

Most of the above examples involve external cues to signal the boundaries between adjacent events. But we also have an inner life, and we can transition between states of mind just as easily as we walk through doors or change conversation partners. In particular, we often transition between different emotional states over time. This week in Nature Communications, McClay and colleagues used music to induce different emotional states and show how fluctuations in these emotional states affect memory formation.

How did they do it?

The authors hired trained film score composers to create emotional musical pieces (choosing from joyous, calm, sad, and anxious), with each piece having three distinct sections with different emotions. These pieces were meant to induce a range of emotions according to the circumplex model of emotion, which holds that emotions can be defined along two main dimensions: arousal and valence. Arousal refers to the energy level of an emotion: high-energy emotions include joy and anxiousness, while low-energy emotions include sadness and calm. Valence refers to the positive or negative quality of an emotion: positive valence emotions include happiness and calm, while negative valence emotions include anxiousness and sadness.

Participants first listened to the pieces in the background while trying to memorize a series of neutral images. At test time, they were presented with two objects and asked which one came first, and also how far apart the objects were in time. Finally, the participants were asked to rate the emotions they felt during the musical pieces using an “Emotional Compass”, a circle that captures a wide range of emotional valence and arousal levels. Participants rated their felt emotions in real-time, moving the mouse around on the Compass while re-listening to the musical pieces. In this way, the authors could extract measures of both the valence and the arousal levels participants experienced at each point in time and could then relate this to their memory performance. They also had a separate group of participants identify musical transitions, where the pitch or complexity changed significantly, so they could factor out the influence of these external sensory boundaries in their analyses.

What did they find?

When two images were separated by a significant emotional transition, people experienced “time dilation” – in other words, they judged the images to be further apart in time than they actually were. Participants also had worse memory for the order of those images. Images that were shown at a boundary transition were better preserved in long-term memory overall (this was tested one day later). These effects are typical of the memory effects seen in previous studies, showing that our experience can be segmented according to our internal states just as much as our external context.

On the other hand, a large shift towards more positive emotions led to item pairs being judged as closer in time (i.e., “time compression”) and people remembered the order of those images better. High-arousal positive emotions also boosted long-term memory for accompanying items: participants could better identify which items were presented as well as when those items were encountered during the sequence. These findings indicate that positive emotions can help to fuse things together in memory, while either being in or shifting towards more negative emotional contexts may instead contribute to memory segmentation and worse memory for timing.

What's the impact?

This work shows that internal emotional states, especially emotional valence, can separate events in memory just like external changes in place and time. It also demonstrates that music is a useful tool for studying emotion in a continuous context in a realistic and reliable way.

Access the original scientific publication here