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Eating only during daytime could protect people from heart risks of shift work

When it comes to cardiovascular health, food timing could be a bigger risk factor than sleep timing.

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A study led by researchers at Mass General Brigham suggests that, when it comes to cardiovascular health, food timing could be a bigger risk factor than sleep timing

Numerous studies have shown that working the night shift is associated with serious health risks, including to the heart. However, a new study from Mass General Brigham suggests that eating only during the daytime could help people avoid the health risks associated with shift work. Results are published in Nature Communications.

“Our prior research has shown that circadian misalignment – the mistiming of our behavioral cycle relative to our internal body clock – increases cardiovascular risk factors,” said senior author Frank A.J.L. Scheer, PhD, a professor of Medicine and director of the Medical Chronobiology Program at Brigham and Women’s Hospital, a founding member of the Mass General Brigham healthcare system. “We wanted to understand what can be done to lower this risk, and our new research suggests food timing could be that target.”

Animal studies have shown that aligning food timing with the internal body clock could mitigate the health risks of staying awake during the typical rest time, which prompted Scheer and his colleagues to test this concept in humans.

For the study, researchers enlisted 20 healthy young participants to a two-week in-patient study at the Brigham and Women’s Center for Clinical Investigation. They had no access to windows, watches, or electronics that would clue their body clocks into the time. The effect of circadian misalignment could be determined by comparing how their body functions changed from before to after simulated night work.

Study participants followed a “constant routine protocol,” a controlled laboratory setup that can tease apart the effects of circadian rhythms from those of the environment and behaviors (e.g., sleep/wake, light/dark patterns). During this protocol, participants stayed awake for 32 hours in a dimly lit environment, maintaining constant body posture and eating identical snacks every hour.  After that, they participated in simulated night work and were assigned to either eating during the nighttime (as most night workers do) or only during the daytime. Finally, participants followed another constant routine protocol to test the aftereffects of the simulated night work. Importantly, both groups had an identical schedule of naps, and, thus, any differences between the groups were not due to differences in sleep schedule.

The investigators examined the aftereffects of the food timing on participants’ cardiovascular risk factors and how these changed after the simulated night work. Researchers measured various cardiovascular risk factors, including autonomic nervous system markers, plasminogen activator inhibitor-1 (which increases the risk of blood clots), and blood pressure.

Remarkably, these cardiovascular risk factors increased after simulated night work compared to the baseline in the participants who were scheduled to eat during the day and night. However, the risk factors stayed the same in the study participants who only ate during the daytime, even though how much and what they ate was not different between the groups—only when they ate.

Limitations of the study include that the sample size was small, although of a typical size for such highly controlled and intensive randomized controlled trials. Moreover, because the study lasted two weeks, it may not reflect the chronic risks of nighttime versus daytime eating.

A strength is that the study participants’ sleep, eating, light exposure, body posture, and activity schedule were so tightly controlled.

“Our study controlled for every factor that you could imagine that could affect the results, so we can say that it’s the food timing effect that is driving these changes in the cardiovascular risk factors,” said Sarah Chellappa, MD, MPH, PhD, an associate professor at the University of Southampton, and lead author for the paper.

While further research is necessary to show the long-term health effects of daytime versus nighttime eating, Scheer and Chellappa said the results are “promising” and suggest that people could improve their health by adjusting food timing. They add that avoiding or limiting eating during nighttime hours may benefit night workers, those who experience insomnia or sleep-wake disorders, individuals with variable sleep/wake cycles, and people who travel frequently across time zones.

In addition to Scheer, Mass General Brigham authors include Lei Gao, Jingyi Qian, Nina Vujovic, Peng Li, and Kun Hu.

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Common drug class may increase risk of heart disease

The risk of cardiovascular disease increased in line with how much anticholinergic medication the participants used each year. Those with the highest exposure had a 71 per cent higher risk of a cardiovascular event than people who did not use anticholinergic medication at all.

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People who use drugs with anticholinergic effects, including certain antidepressants, drugs for urinary incontinence and common antihistamines, are at higher risk of developing cardiovascular disease.

This is shown in a study from Karolinska Institutet published in BMC Medicine.

Anticholinergic drugs reduce the effect of the neurotransmitter acetylcholine and are commonly prescribed to middle-aged and older people. This large group of drugs includes antihistamines used for allergic conditions, anxiety or insomnia, drugs for urinary incontinence, and certain antidepressants, where tricyclic antidepressants have a strong anticholinergic effect, whereas SSRIs have a weaker effect. A high cumulative use of these drugs, referred to as anticholinergic burden (see fact box), has previously been linked to impaired cognitive ability. 

May affect heart regulation 

The new study suggests that the drugs may also affect the parasympathetic nervous system and thereby the regulation of the cardiovascular system. The results show that it may be important to monitor the total drug burden in everyday clinical practice.

The study included more than 500,000 people in Stockholm, Sweden, who were 45 years of age or older and had no prior cardiovascular disease, except for hypertension, at the start of the study. The researchers followed the participants for up to 14 years and analysed how the use of anticholinergic drugs was associated with the development of cardiovascular disease.

“Many of these drugs are used by older people and by people with multiple medical conditions. We wanted to investigate whether the total exposure had any significance for the risk of developing cardiovascular disease over time,” says Nanbo Zhu, postdoctoral researcher at the Department of Neurobiology, Care Sciences and Society, Karolinska Institutet.

71 per cent higher cardiac risk

The study showed that the risk of cardiovascular disease increased in line with how much anticholinergic medication the participants used each year. Those with the highest exposure had a 71 per cent higher risk of a cardiovascular event than people who did not use anticholinergic medication at all. The association was seen for all types of cardiovascular disease but was particularly clear for heart failure and various forms of arrhythmia.

“Our results indicate that the cumulative drug burden can affect heart regulation, not only in the short term but also over the long term. This does not mean that the drugs should always be avoided, but that exposure should be monitored carefully,” says Hong Xu, assistant professor at the Department of Neurobiology, Care Sciences and Society.

The researchers point out that the study is observational, meaning it cannot establish a causal relationship. Other factors, such as underlying diseases, may also influence the associations.

The work was carried out within the Stockholm CREAtinine Measurements project in collaboration between several research groups at Karolinska Institutet and Region Stockholm. The study was funded by the Swedish Research Council, the Center for Innovative Medicine Foundation, and other foundations. Some researchers report assignments for the pharmaceutical industry, which are disclosed in the scientific publication.

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Mindfulness practices found to significantly reduce depression symptoms, especially for those with early-life adversity

Mindfulness interventions help by regulating our emotions better when different challenges come up. For someone who has experienced childhood neglect or abuse, mindfulness training can help us make sense of that and respond skillfully to this moment in time.

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A new study reveals that mindfulness practices may significantly reduce depression symptoms, particularly in people who have experienced early-life adversity, such as childhood abuse and neglect.

Led by Eric Loucks, professor of medicine, epidemiology, and of behavioral and social sciences and director of the Mindfulness Center at Brown, the study enrolled 201 participants, 101 of whom were randomized into the Mindfulness-Based Blood Pressure Reduction Program, while 100 were randomized into an enhanced usual care control, which included home blood-pressure monitors, physician access and health-education materials. Researchers also had a measure of participants’ early-life adversity, particularly their exposure to abuse or neglect.

Loucks and his team followed participants for six months to assess changes in blood pressure, health behaviors and mental health, finding that those in the mindfulness program showed significant improvements in their depression symptoms. Additionally, participants who experienced childhood neglect showed greater improvements in depression symptoms than those who had not. A similar, though less pronounced, trend was observed among people with a history of childhood abuse.

“In this program, that was primarily designed to lower blood pressure while addressing whole-person health, we also saw that mental well-being, particularly around depression symptoms, improved in participants that went through the program,” Loucks said. “The findings suggest that cultivating mindful self-regulation skills–such such as self-awareness, attention control and emotion regulation–may help interrupt maladaptive patterns shaped by past experiences.”

Over the last 15 years, Loucks has been studying social determinants of health such as early-life adversity and its impacts on cardiovascular health, body mass index and blood pressure. “I came to a point where I wanted to not just document it, but do something about it, and I wondered if mindfulness training might help,” he said. “I’d gone through a lot of mindfulness training myself outside of work and started to get trained up in mindfulness programs that are specific to health contexts.”

Loucks began to study the Mindfulness-Based Stress Reduction program, running it through two clinical trials that were funded by the NIH and finding that it reduced blood pressure in both trials. He also wanted to look at the intervention from a whole-person perspective.

“If we look at everyday folks out in the world, those that had exposure to early life adversity, like abuse and neglect, tend to have worse mental health and also worse cardiovascular health,” Loucks said. “Mindfulness interventions help by regulating our emotions better when different challenges come up. For someone who has experienced childhood neglect or abuse, mindfulness training can help us make sense of that and respond skillfully to this moment in time.” 

Loucks discussed this work during a keynote address at the U.S. DOHaD Society this year. “It felt like a coming-home moment to see that this intervention, originally developed to address psychosocial factors that influence health, had even stronger effects among people with early-life adversity, particularly on depression,” he said. “It’s been about a 15-year arc of research that culminated in these findings.”

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High-fiber diet linked to reduced risk of heart disease in night shift workers

A moderate intake of about 19 grams of fibre per day was linked to a lower risk for those who worked night shifts regularly. For those who worked night shifts sporadically, about 15 grams was enough. The current recommendation for adults is about 25 grams of dietary fibre per day.

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People who work at night have a higher risk of coronary artery disease, a type of heart disease. A new study suggests that a higher fibre intake in the diet may help reduce this risk. The study included over 220,000 adults in the UK and is published in the European Journal of Epidemiology.

The human body is built to sleep at night. This means that working during the night goes against this natural pattern, and can place additional strain on the body, including the heart. Previous research has linked night work to an increased risk of coronary artery disease. Since night work is often unavoidable, the researchers wanted to investigate whether certain dietary habits might have a protective effect.

More fibre associated with lower risk

The researchers used data from 220,000 adults in the UK Biobank (2006–2010) and divided the participants into three groups:

  • Day workers
  • Shift workers who worked night shifts sporadically
  • Regular night shift workers

The participants had completed a detailed questionnaire about their dietary habits. During a follow-up after about 12 years, it was found that night shift workers who consumed little fibre in their diet had a higher risk of coronary artery disease than those who consumed more fibre.

“A moderate intake of about 19 grams of fibre per day was linked to a lower risk for those who worked night shifts regularly. For those who worked night shifts sporadically, about 15 grams was enough. The current recommendation for adults is about 25 grams of dietary fibre per day,” says Diana Nôga, lead author and researcher at Uppsala University.

The researchers stress that the figures from the study are not official dietary recommendations. But they do show a pattern in this UK study: a higher dietary fibre intake was linked to a lower risk of heart disease among night shift workers.

“The link between fibre and a lower risk of heart disease is not just because those who eat more fibre generally have a healthier lifestyle. We know this because we adjusted for various lifestyle factors in the analysis. One possible explanation, supported by previous research, is that fibre in the diet can improve intestinal flora and also reduce lipids, which can be particularly good for the heart in people who work at night,” says Christian Benedict, senior author of the study and Professor of Pharmacology at Uppsala University.

Dietary fibre can support heart health

According to the researchers, an increased intake of fibre-rich foods such as whole grains, vegetables, fruit, legumes and lentils may be a simple way to improve heart health for night shift workers. However, this requires that you do not have any medical obstacles to doing this, such as chronic gastrointestinal diseases.

“Dietary changes should be seen as a complement to, not a substitute for, other heart health-promoting habits such as not smoking, remaining physically active, and getting enough sleep,” says Diana Nôga.

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