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Exposure to traffic noise linked to higher dementia risk

Reducing noise is a public health priority, say experts.

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Photo by Hermes Rivera from Unsplash.com

Exposure to noise from traffic on roads and railways over a long period is associated with a higher risk of developing dementia, especially Alzheimer’s disease, suggests a study from Denmark published in The BMJ

The researchers estimate that as many as 1,216 out of the 8,475 cases of dementia registered in Denmark in 2017 could be attributed to these noise exposures, indicating a great potential for dementia prevention through reduction in traffic related noise. 

Worldwide, the number of people with dementia is expected to exceed 130 million by 2050, making it a costly and growing global health crisis. Besides well established risk factors, such as cardiovascular diseases and unhealthy lifestyle, environmental exposures may also play a role in the development of dementia.

Transportation noise is considered the second worst environmental risk factor for public health in Europe after air pollution, and around a fifth of the European population is exposed to transportation noise above the recommended level of 55 dB (decibels).

Studies have consistently linked transportation noise to various diseases and health conditions, such as coronary heart disease, obesity, and diabetes. There is, however, little research on transportation noise and dementia and findings are inconsistent.

To address this, researchers investigated the association between long term residential exposure to road traffic and railway noise and risk of dementia among two million adults aged over 60 and living in Denmark between 2004 and 2017. 

The researchers estimated road traffic and railway noise at the most and least exposed sides (or façades) of all residential addresses in Denmark. 

They then analysed national health registers to identify cases of all-cause dementia and different types of dementia (Alzheimer’s disease, vascular dementia, and Parkinson’s disease related dementia) over an average of 8.5 years.

They found 103,500 new cases of dementia during the study period.

After taking account of potentially influential factors related to residents and their neighbourhoods, the researchers found that a 10-year average exposure to road traffic and railway noise at the most and least exposed sides of buildings was associated with a higher risk of all-cause dementia.

These associations showed a general pattern of higher risk with higher noise exposure, but with a levelling off or even small declines in risk at higher noise levels.

Further analysis by type of dementia showed both road traffic and railway noise were associated with a higher risk of Alzheimer’s disease – up to 27% higher for exposure to road traffic noise of 55 dB and up to 24% higher for exposure to railway noise of 50 dB compared with less than 40 dB.

However, only road traffic noise was associated with an increased risk of vascular dementia, and not railway noise.

Possible explanations for an effect of noise on health include release of stress hormones and sleep disturbance, leading to a type of coronary artery disease, changes in the immune system and inflammation – all of which are seen as early events in the onset of dementia and Alzheimer’s disease.

This is an observational study so can’t establish cause, and the authors point to some limitations such as a lack of information about lifestyle habits, which can play a part in a person’s risk of developing dementia, and a lack of information on factors such as sound insulation in homes that might affect personal exposure to noise.

However, the study’s strengths included its large size, long follow-up time, and high quality assessment of noise exposure from two different transportation sources.

As such, the authors conclude: “If these findings are confirmed in future studies, they might have a large effect on the estimation of the burden of disease and healthcare costs attributed to transportation noise. Expanding our knowledge on the harmful effects of noise on health is essential for setting priorities and implementing effective policies and public health strategies focused on the prevention and control of diseases, including dementia.”

This large and comprehensive study has substantial strengths, but does not present the full picture of possible harm to the ageing brain associated with long term exposure to noise, for example from airports, industrial activities, or occupational exposure, say US researchers in a linked editorial.

Noise might also affect the risk of other chronic disorders such as high blood pressure, through which noise contributes indirectly to dementia risk, they add. 

The widespread and substantial exposures to noise worldwide, the severity of associated health consequences, and the limited tools available for people to protect themselves, strongly support the WHO’s argument that “noise pollution is not only an environmental nuisance but also a threat to public health,” they write.

“Reducing noise through transportation and land use programs or building codes should become a public health priority,” they conclude.

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For people with migraine, feelings of stigma may impact disability, quality of life

For people with migraine, these feelings of stigma were linked to more disability, increased disease burden and reduced quality of life.

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Migraine can impact many aspects of a person’s life, but less is known about how feelings of stigma about the disease affect quality of life. For people with migraine, these feelings of stigma were linked to more disability, increased disease burden and reduced quality of life, according to new research published in the online issue of Neurology, the medical journal of the American Academy of Neurology.

“Stigma is common where the disease is not readily apparent to others, and there is indication that it could be especially relevant for those living with migraine,” said study author Robert Evan Shapiro, MD, PhD, of the University of Vermont and Fellow of the American Academy of Neurology. “This stigma may arise when a person with migraine recognizes negative stereotypes about the disease and experiences shame for having the disease, fear of experiencing stigma from others, or other negative emotions.”

For the study, researchers looked at 59,001 people with migraine with an average age of 41. Among all participants, 41% reported experiencing four or more headache days per month on average.

Participants answered 12 questions to assess two types of stigma: whether they felt others viewed migraine being used for secondary gain and whether they felt others were minimizing the burden of migraine. Questions included “How often have you felt that others viewed your migraine as a way to get attention?” “… as something that made things difficult for your co-workers or supervisor?” and “…with a lack of understanding of the pain and other symptoms?”

Researchers found that 32% of the participants experienced migraine-related stigma often or very often.

To assess migraine-related disability, participants reported the number of days they missed or had reduced productivity at work, home or social events over the previous three months. High scores on migraine-related stigma were linked with moderate to severe disability. Three-quarters of those who experienced stigma often or very often had moderate to severe disability, compared to 19% of those who never experienced stigma.

They also took a test assessing migraine-specific quality of life, which looked at the impact of migraine on social and work-related activities over the previous four weeks. Scores ranged from zero to 100 with higher scores meaning higher quality of life. Researchers found that those who experienced the highest rates of migraine-related stigma scored far lower in these tests, with an average score of 35 compared to those who did not experience stigma with an average score of 69.

The results remained the same after researchers adjusted for other factors that could affect disability and quality of life, such as age, employment status, other medical conditions and frequency of migraines.

They also found that the amount of stigma experienced increased with migraine severity. Those with 8-14 headache days or more than 15 monthly headache days were far more likely to report at least one form of stigma with 42% and 48%, respectively, compared to those with less than four monthly headache days with 26%.

“The social context of migraine may have a greater impact on quality of life than the number of monthly headache days,” said Shapiro. “However, it is possible that connecting with others with migraine may help decrease migraine-related stigma and stereotypes. More studies are needed to explore the mechanisms that link stigma to health outcomes.”

A limitation of the study was that participants self-reported their migraines, based on a questionnaire or a diagnosis from a health care provider, and they may not have remembered all the information accurately.

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Alcohol raises heart disease risk, particularly among women

Young to middle-aged women who reported drinking eight or more alcoholic beverages per week—more than one per day, on average—were significantly more likely to develop coronary heart disease compared with those who drank less.

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Young to middle-aged women who reported drinking eight or more alcoholic beverages per week—more than one per day, on average—were significantly more likely to develop coronary heart disease compared with those who drank less, finds a study presented at the American College of Cardiology’s Annual Scientific Session. The risk was highest among both men and women who reported heavy episodic drinking, or “binge” drinking, and the link between alcohol and heart disease appears to be especially strong among women, according to the findings.

The study focused on 18- to 65-year-old adults and is among the largest and most diverse studies to date examining the links between alcohol and heart disease. Heart attacks and other forms of heart disease are on the rise in younger populations in the U.S., fueling concern about worsening health outcomes. At the same time, alcohol use and binge drinking have become more common among women than in previous decades.

“When it comes to binge drinking, both men and women with excess alcohol consumption had a higher risk of heart disease,” said Jamal Rana, MD, PhD, FACC, a cardiologist with The Permanente Medical Group, adjunct investigator in the Division of Research at Kaiser Permanente Northern California and the study’s lead author. “For women, we find consistently higher risk even without binge drinking. I wasn’t expecting these results among women in this lower age group because we usually see increased risk for heart disease among older women. It was definitely surprising.”

The researchers used data from more than 430,000 people who received care in the Kaiser Permanente Northern California integrated health organization, including nearly 243,000 men and 189,000 women. Participants on average were 44 years old and did not have heart disease at the start of the study. Information on participants’ alcohol intake was collected during primary care visits using the health organization’s standard “Alcohol as a Vital Sign” screening initiative, which includes visual reference posters to help patients estimate alcohol quantities according to standard measurements.

Researchers analyzed the relationship between the level of alcohol intake participants reported in routine assessments from 2014-2015 and coronary heart disease diagnoses during the four-year period that followed. Coronary heart disease occurs when the arteries that supply blood to the heart become narrowed, limiting blood flow. This condition can cause chest pain and acute events, such as a heart attack.

Based on self-report assessments, researchers categorized participants’ overall alcohol intake as low (one to two drinks per week for both men and women), moderate (three to 14 drinks per week for men and three to seven drinks per week for women), or high (15 or more drinks per week for men and eight or more drinks per week for women). They separately categorized each participant as either engaging in binge drinking or not. Binge drinking was defined as more than four drinks for men or more than three drinks for women in a single day in the past three months. People who reported no alcohol use were not included in the study. The researchers adjusted the data to account for age, physical activity, smoking and other known cardiovascular risk factors.

Overall, 3,108 study participants were diagnosed with coronary heart disease during the four-year follow-up period, and the incidence of coronary heart disease increased with higher levels of alcohol consumption. Among women, those who reported high alcohol intake had a 45% higher risk of heart disease compared with those reporting low intake and had a 29% higher risk compared with those reporting moderate intake. The difference was greatest among individuals in the binge drinking category; women in this category were 68% more likely to develop heart disease compared with women reporting moderate intake. Men with high overall intake were 33% more likely to develop heart disease compared with men who had moderate intake.

“Women feel they’re protected against heart disease until they’re older, but this study shows that even when you’re young or middle aged, if you are a heavy alcohol user or binge drink, you are at risk for coronary heart disease,” Rana said.

The results showed no significant difference in risk between people who reported moderate versus low alcohol intake, regardless of whether they also were categorized as binge drinking.

Alcohol has been shown to raise blood pressure and lead to metabolic changes that are associated with inflammation and obesity. Women also process alcohol differently than men. Researchers said the study calls attention to the health risks of alcohol consumption and underscores the importance of considering alcohol use in heart disease risk assessment and prevention efforts. 

“When it comes to heart disease, the number one thing that comes to mind is smoking, and we do not think about alcohol as one of the vital signs,” Rana said. “I think a lot more awareness is needed, and alcohol should be part of routine health assessments moving forward.”

One limitation of the study is that people tend to under-report their alcohol intake when asked by a health care provider. As a result, the study likely provides conservative estimates of the heart disease risk associated with alcohol consumption. The researchers also said the manner in which alcohol screening is performed in a health clinic can influence how patients and clinicians discuss the risks of alcohol consumption, and that further research could help determine optimal strategies.

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Aerobic exercise can help fight liver diseases

he Mfn-2 protein would regulate the curve of the mitochondrial membrane in promoting the oxidation of fat in a specific population of mitochondria, through its interaction and ability to form specific domains with membrane phospholipids.

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Aerobic exercise could help fight the non-alcoholic fatty liver disease, the most common liver disease worldwide: it affects nearly 24% of the global population and it usually causes a certain stigma among the affected people.

This is according to a study – “Mitofusin-2 induced by exercise modifies lipid droplet-mitochondria communication, promoting fatty acid oxidation in male mice with NAFLD” that appeared in the journal Metabolism. The study was led by Professor María Isabel Heràndez-Alvarez, in collaboration with Rodrigo Troncoso, and Víctor Cortés.  

When the liver accumulates large amounts of fat

One of the features of the fatty liver disease or non-alcoholic steatohepatitis (NAFLD) is the large concentration of lipid droplets (LD) that accumulate in the liver cells. “Our findings reveal that aerobic exercise, that is, moderate physical activity over time, helps metabolize the fats because it reduces the size of lipid droplets, and therefore, the severity of the disease”, notes the author. 

“Therefore, the energy demands induced by the exercise determine regulated changes in physical and functional relationships between fat droplets and mitochondria, the cell organelles that provide energy for the metabolism.”

This interaction may take place in a specific population of mitochondria known as peridroplet mitochondria (PDM). “As a result, there is a higher oxidation of lipids in this specific population of mitochondria, a process that helps prevent the progress of the disease”.

Discovering a previously unknown connection

“The interaction between the lipid droplets (LD) and the mitochondria is functionally important for the homeostasis of the fat metabolism. Exercise improves fatty liver disease, but to date, it was unknown whether the disease had a direct impact on the interactions between hepatic LDs and mitochondria,” noted María Isabel Hernàndez-Alvarez, Ramón y Cajal postdoctoral researcher at the UB’s Department of Biochemistry and Molecular Biomedicine.

The study also stresses that mitofusin 2 (Mfn-2) — a protein located in the external membrane of mitochondria — plays a decisive role in this process, since it modifies the communication between lipid droplets and the specific population of mitochondria.

“We found a decrease in the content related to saturated fatty acids in the hepatic mitochondrial membranes of animals that had done physical activity. This suggests that membrane fluidity increases in the mitochondria,” noted the researcher. “In the case of the mice without the Mfn-2 gene, exposed to physical activity, we did not observe changes in the saturation and the metabolism of fatty acids. These results show that the Mfn-2 protein takes part in the regulation of the composition of fatty acids of the mitochondrial membranes in response to exercise”.

According to the authors, the Mfn-2 protein would regulate the curve of the mitochondrial membrane in promoting the oxidation of fat in a specific population of mitochondria, through its interaction and ability to form specific domains with membrane phospholipids.

The study is a step forward to boosting research on mediators and molecular mechanisms that could promote new strategies to prevent the progression of NAFLD. “Considering the Mfn-2 functions in mitochondrial morphology and in the liver, the therapeutic manipulations of the levels and the activity of Mfn-2 could contribute to the improvement of the NAFLD-related inflammation and the fibrosis”, concluded the researcher.

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