HKU ecologists warn that marine heatwaves pose an underestimated threat to public health

The University of Hong Kong

Facebook

XLinkedInWeChatBlueskyMessageWhatsAppEmail

 

image: 

The average number of days of marine heatwaves annually projected for mid-century. Image courtesy Prof. Ben Harvey.

view more 

Credit: Prof. Ben Harvey

Researchers from the School of Biological Sciences and Swire Institute of Marine Science (SWIMS) at The University of Hong Kong (HKU), in collaboration with Adelaide University, have called for marine heatwaves to be recognised as a public health issue.

The research, published in Nature Sustainability, highlights that marine heatwaves not only damage marine ecosystems but can also intensify extreme weather, disrupt fisheries and aquaculture, reduce seafood supplies and threaten coastal livelihoods, ultimately posing significant risks to human physical and mental health.

How Marine Heatwaves Affect Human Health

Marine heatwaves, prolonged periods of unusually high ocean temperatures, are becoming more frequent, longer-lasting and more intense as the climate warms. While their impacts on marine ecosystems are well documented, their consequences for human health remain largely overlooked.

Key Impacts Identified

• Extreme weather: Higher ocean temperatures can contribute to more intense storms and flooding, increasing the risk of injury, death, and displacement.
• Food safety: Marine heatwaves can increase harmful algal blooms that contaminate seafood and pose health risks.
• Food security and nutrition: Damage to fisheries and aquaculture can reduce seafood supplies, particularly affecting communities that rely heavily on marine resources.
• Livelihoods and mental health: Damage to marine ecosystems and loss of income can contribute to stress, anxiety, grief and uncertainty.
• Ocean-dependent communities: The impacts are particularly relevant in Asia, where hundreds of millions of people depend on the ocean for food, livelihoods and cultural practices.

 “The devastating effects of marine heatwaves on marine ecosystems have been recognised for some time. What has been missing from the conversation is what these events mean for people. We are only just beginning to understand how these environmental impacts can have large negative effects on human health,” said Professor Bayden RUSSELL, Associate Professor of Ecology & Biodiversity and senior author of the paper.

He added: “For many people, the ocean is much more than a place for recreation. It provides food, income, cultural identity and a sense of place.” These close connections to the ocean mean that damage to marine ecosystems can also have significant psychological impacts. “When marine heatwaves damage coral reefs, fisheries and other marine resources, communities can experience grief, anxiety and uncertainty about the future. These mental health impacts are likely to be substantial, but they remain largely unrecognised and understudied.”

The researchers argue that governments and public health agencies should begin treating marine heatwaves much like land-based heatwaves. This includes incorporating marine heatwave forecasts into public health planning, considering health impacts in marine and coastal management, and strengthening collaboration between ocean scientists, health authorities and resource managers.

Dr Laura FALKENBERG of Adelaide University said: “Recognising these health impacts is the first step towards better protecting communities.”

“As marine heatwaves become increasingly common, we need to move from simply documenting impacts after they occur to preparing communities in advance. Better planning today can reduce future health risks.”

For details of the research, please refer to the journal paper “Recognising the human health impacts of marine heatwaves”.  

Media Enquiries:
Faculty of Science, The University of Hong Kong
Tel: +852 3917 5286
Email: cindycst@hku.hk

Image download and caption: https://www.scifac.hku.hk/press

---

Journal

Nature Sustainability

DOI

10.1038/s41893-026-01892-x 

Method of Research

Observational study

Subject of Research

Not applicable

Article Title

Recognizing the human health impacts of marine heatwaves

 

Healthy lifestyle in middle age adds happiness alongside longevity to old age

University of Helsinki

LinkedInWeChat
WhatsAppEmail

University of Helsinki researchers followed almost 2,700 Finnish men for over 50 years, until the end of their lives. The monitoring began in the 1960s and 1970s, when the men were on average 42 years old and healthy.

The researchers measured five factors contributing to cardiovascular risk: smoking, body mass index, blood pressure, cholesterol and blood glucose. The better the values for each factor, the longer the men lived.

Of the men with positive values for all five factors, 42% reached the age of 90. The corresponding figure for those with poor values for all five was 7%.

Not just more years, but better ones

The study did not stop at measuring lifespan. In 2007, when the surviving research subjects averaged 79 years of age, they were asked about their functional capacity, happiness and quality of life.

At the same time, their degree of frailty was also assessed. Of those for whom all five factors were positive at a younger age, only 2% were frail in old age. The same group also experienced more happiness and psychological wellbeing than others. Of those with poor values for all factors, a quarter were frail.

“The common adage is that you either live a short and pleasant life, or a long and unpleasant one. This study indicates that healthy lifestyles can add both years and functional capacity to your life,” says Professor Emeritus Timo Strandberg from the University of Helsinki’s Faculty of Medicine and HUS Helsinki University Hospital, who headed the study.

Common solutions

Strandberg emphasises the simplicity of the indicators used in the study and their applicability to anyone’s everyday life.

“The body mass index, smoking, cholesterol, blood pressure and blood glucose can all be measured and addressed. If not through lifestyle choices, then with safe and mostly inexpensive drugs,” Strandberg says.

What makes this study distinct is its duration – the men were followed throughout adulthood.

“We’ve long been interested in this question, while in many places the topic is only now attracting attention. This study’s strength was in a follow-up that extended to the end of life,” Strandberg notes.

As the population ages, the need for care increases. According to Strandberg, the study provides new motivation for addressing risk factors even before problems arise.

---

Journal

European Journal of Preventive Cardiology

DOI

10.1093/eurjpc/zwag429 

Subject of Research

People

Article Title

Low cardiovascular risk in early midlife and quality of life in old age: a life-long follow-up study in men

 

Incidence of acute kidney injury is higher in summer, especially among young people in Japan

Large-scale health insurance data reveal a seasonal pattern in community-acquired acute kidney injury, highlighting the importance of summer prevention

Kumamoto University

Facebook

XLinkedInWeChatBlueskyMessageWhatsAppEmail

 

image: 

Compared to February, the adjusted incidence rate was significantly higher from June through September, reaching its peak in July and June with an adjusted incidence rate ratio of 1.19. Younger populations, particularly those aged 19 years and younger, showed a larger seasonal increase in AKI incidence during the summer peak.

Adapted from Sakazaki et al., Scientific Reports (2026), licensed under Creative Commons Attribution 4.0 International (CC BY 4.0).

view more 

Credit: Kumamoto University

A new study led by researchers at Kumamoto University has found a clear seasonal pattern in community-acquired acute kidney injury (AKI) among people younger than 65 years in Japan, with incidence peaking in summer and showing a larger seasonal increase among those aged 19 years and younger.

AKI is a sudden decline in kidney function that can become serious enough to require hospitalization or dialysis. While AKI is often associated with hospitalized patients, it can also develop in the community, including among people who are otherwise living their everyday lives and visiting outpatient clinics.

The research team analyzed health insurance claims data from approximately 4.28 million people under 65 years of age in Japan, covering the period from August 2016 through July 2018. Among them, 20,634 new cases of community-acquired AKI were identified.

The incidence of AKI increased from June to July and reached its highest level in July. Compared with February, the adjusted incidence rate in July was 19% higher (IRR 1.19). Among people aged 0–19 years, the July incidence rate was approximately 48% higher than in February (IRR 1.48), indicating a larger seasonal variation in this age group.

“Summer is a season when dehydration and heat-related health problems can become more common,” said Yuka Sakazaki, the study’ first author and a doctoral student at Kumamoto University’s Graduate School of Medical Sciences. “Our findings suggest that seasonal factors may be important to consider in AKI prevention, especially given the larger seasonal variation observed among younger people.” added Yuki Kondo, the corresponding author and an Associate Professor at Kumamoto University’s Faculty of Life Sciences.

The researchers caution that the study does not establish that high temperatures or dehydration directly cause AKI. The claims database did not contain laboratory measurements or detailed information on individual heat exposure, temperature, humidity, or other environmental conditions. In addition, AKI was identified using diagnosis codes in insurance claims rather than laboratory-based diagnostic criteria, so differences in diagnosis or coding across seasons cannot be completely excluded.

Future research combining clinical and laboratory data with meteorological information may help clarify how environmental factors contribute to seasonal changes in AKI risk and support the development of prevention strategies tailored to the summer season.

---

Journal

Scientific Reports

DOI

10.1038/s41598-026-61190-6 

Method of Research

Observational study

Subject of Research

People

Article Title

Seasonality of acute kidney injury incidence in Japanese outpatient

 

More injuries following the policy change of body-checking in women’s ice hockey – but the players are positive about the change

Lund University

Facebook

XLinkedInWeChatBlueskyMessageWhatsAppEmail

 

image: 

Amanda Lahti

view more 

Credit: Ingemar Hultquist, Lund University

Four years after body-checking was introduced, have injury rates in Swedish women’s ice hockey changed? Yes, markedly. Researchers at Lund University in Sweden have now been able to show that, in the short term, the number of insurance claims almost doubled.

In 2022, body-checking became permissible in the SDHL, the top-flight Swedish women’s ice hockey league. Sweden was thus the first country in the world to make this change, and the research is being followed with great interest by other ice hockey nations. Both the US and Canada have also recently started to allow body-checking and are keen to know what impact the change has had in Sweden. There are now two recent research studies from Lund University.

One of the studies is based on insurance data covering six seasons, in which all ice hockey-related injuries that led to a claim under the players’ licence insurance were recorded by the insurance company. During the first season after body-checking was introduced, the number of reported injuries soared. Having stood at 6.6 injuries per 1,000 player-hours in the season before the rule change, the figure rose to 16.7 injuries per 1,000 player-hours the following season. The number of injuries then fell slightly, but the average for the six seasons studied was 11. The average for the corresponding period before the rule change was 6.0.

“Injury rates may continue to fall as players adapt to the physical nature of play, but that remains to be seen. It is not possible to say with certainty that the higher injury figures are due to body-checking, but we speculate that this is the case, as everything else remains the same compared with previous seasons,” says Amanda Lahti, a researcher at the Centre for Primary Care Research, Lund University, and the lead author of both studies and the primary investigator (PI) for the research project.

Shoulder and knee injuries were the most common claims handled by the insurance company, which Amanda Lahti speculates may be because players take body-checks against the boards with their arms outstretched. According to her, the fact that the figures are levelling off could possibly be interpreted as the players learning to play a more physical game over time.

The second study identified injuries that resulted in absence from training or matches and were added to an injury register by the medical staff in the league. A total of 46 match-related injuries were recorded. The results show that body-checking is now the most frequent cause of injury and is often associated with concussion, the most common type of injury in the league. The study also showed that players often continued to play in the games despite being injured. In six out of ten cases of concussion, the player remained on the ice. Most of the injuries, including concussions, occurred in the third period, towards the end of the game. This could suggest that fatigue increases the risk of injury.

“Perhaps it’s not just a case of tiredness after a tough match. As female ice hockey players generally earn less than their male counterparts, many combine elite sport with paid work, which can limit their recovery and contribute to increased fatigue. I would like to go on and gain a deeper understanding of how sleep and recovery might affect the risk of injury,” says Amanda Lahti.

She emphasises that the study tracked the development of injuries over only two years and is based on a relatively small number of injury incidents, which means that the results should be interpreted with some caution. Nevertheless, the findings raise questions and form the basis for further research. Female athletes should not be regarded as “little men”. Biological, anatomical and social differences influence the risk of sports injuries. Yet only a small proportion of sports medicine research is carried out on women.

“This makes women-specific studies essential. Although this study has its limitations, it provides important insights and baseline data for the continued monitoring of the cohort and the progression of injuries over time,” says Amanda Lahti. As a specialist in general medicine and a sports doctor, she works on the prevention of injuries on a daily basis.

The results also show that the players themselves remain positive about body-checking – and that they do not believe it leads to more injuries.

“I will be examining this discrepancy between the players’ own perceptions and our objective injury data in more detail in a forthcoming paper. Amongst other things, I have sought the help of a gender researcher from the IOC (International Olympic Committee) to gain a better understanding of this,” says Amanda Lahti.

Hopefully, at least some of her questions will eventually be answered. She recently received a grant of SEK 1.2 million from the Dr P Håkansson Foundation.

“This is a very significant grant, which I hope will help generate more knowledge that promotes women’s participation in sport at both recreational and elite levels, as well as contributing to the development of the sport,” says Amanda Lahti. 

Related publication
Injury Incidence Before and After the Introduction of Body Checking in Elite Women’s Ice Hockey: A Six-Season Nationwide Insurance-Based Study, Sports Medicine – Open
DOI: 10.1186/s40798-026-01063-4 

 

---

Journal

European Journal of Sport Science

DOI

10.1002/ejsc.70245 

Method of Research

Case study

Subject of Research

People

Article Title

Epidemiology of Injuries in Elite Female Ice Hockey Players Allowed Body Checking: A Two-Year Prospective Cohort Study

AROMATHERAPY

Using Japanese Igusa (rush grass) may enhance mood, stress resilience, and task engagement

EEG tests show that Igusa use is associated with increased activity in brain regions related to concentration and engagement

Kyushu University

LinkedInWeChatBlueskyMessageWhatsAppEmail

 

image: 

Igusa is the core material used in making tatami mats. After Igusa is cultivated, it is dried and woven into mats. These mats are then sewn onto the tatami’s base. Over 90% of Igusa grown in Japan comes from a single region: Yatsushiro City in Kumamoto Prefecture on the island of Kyushu.

view more 

Credit: Yousuke Konno

Fukuoka, Japan—Publishing in the journal Scientific Reports, researchers at Kyushu University found that using mats made from Japanese Igusa, or rush grass, was associated with increased activity in regions of the brain related to concentration and engagement. Furthermore, surveyed participants reported reduced tension and anxiety after using Igusa mats. Igusa has been used in Japan for centuries, and the research team hopes scientific evidence on its health benefits will provide new value for this traditional material.

What is the first thing you notice when you walk into a Japanese-style room? Is it the floor-level furniture? The sliding wood-and-paper doors? Or is it the smell? Also called a tatami room—or Washitsu in Japanese—these spaces are defined by their tatami flooring, which has been part of Japanese culture and architecture for centuries. The unique smell of the Washitsu comes from the tatami, specifically the Igusa that makes up the mat surface.

“In Japan, the scent of Igusa is associated with comfort and relaxation. However, there is very little scientific evidence to support such claims,” explains Associate Professor Kuniyoshi Shimizu from Kyushu University’s Faculty of Agriculture, who led the study. “Our team has been using objective scientific methods to investigate the effects of Igusa on people. Previously, we showed that the aromatic compounds in Igusa have relaxing effects. This time we wanted to explore other benefits like mood, stress resilience, and task engagement.”

In their experimental setup, the team placed volunteers in a soundproof room under two conditions: sitting on Igusa mats or sitting on unscented polypropylene plastic mats. The volunteers then completed simple tasks while the team measured their reaction time and brain activity using an electroencephalograph (EEG). Afterward, the team conducted psychological questionnaires to assess the volunteers’ stress and comfort.

“We had a total of 17 volunteers with an average age of 21.5 years. When we compared the results of tasks performed on the Igusa mat with the control conditions, we saw a significant difference,” explains Shimizu. “The EEG results showed that when participants were sitting on the Igusa mats while completing their tasks, they had increased beta wave activity in certain parts of the brain. This indicates that they had enhanced focus and better cognitive engagement.”

Moreover, the team found that under Igusa mat conditions, gamma wave activity showed clear changes between resting and task periods across many brain areas. Alpha wave activity also remained more stable during rest periods. Together, these patterns suggest increased stress resilience through more efficient relaxation.

Afterward, volunteers reported reduced tension and anxiety after using the Igusa mats. However, other aspects of mood showed no significant change.

This study provides new empirical data on the possible benefits of Igusa mats, specifically their potential to reduce tension and anxiety as well as to support stress resilience when performing tasks.

“We had a small number of participants in this study, so the next step is to replicate the experiment with a larger, more diverse population. In addition, we only evaluated short-term responses, so we would also like to investigate the long-term effects of Igusa use,” concludes Shimizu. “For generations, Igusa has brought comfort to Japanese living spaces. But today, its use has decreased due to changes in lifestyles and modern housing environments. Through our research, we hope to deepen our understanding of how traditional materials can influence people and discover new applications for them in contemporary society.”

###

For more information about this research, see "Stress resilience and engagement enhancement under the usage of Igusa (Juncus effusus L. var. decipiens Buchen.) mat: a crossover study," Fadilla Zennifa, Yanli Xu, Akiko Isa, Erika Tomimatsu, Ziyou Xu, Yousuke Konno, Masataka Ikegami, Kuniyoshi Shimizu, in Scientific Reports, https://doi.org/10.1038/s41598-026-47520-8

About Kyushu University 
Founded in 1911, Kyushu University is one of Japan's leading research-oriented institutions of higher education, consistently ranking as one of the top ten Japanese universities in the Times Higher Education World University Rankings and the QS World Rankings. Located in Fukuoka, on the island of Kyushu—the most southwestern of Japan’s four main islands—Kyushu U sits in a coastal metropolis frequently ranked among the world’s most livable cities and historically known as Japan’s gateway to Asia. Its multiple campuses are home to around 19,000 students and 8,000 faculty and staff. Through its VISION 2030, Kyushu U will “drive social change with integrative knowledge.” By fusing the spectrum of knowledge, from the humanities and arts to engineering and medical sciences, Kyushu U will strengthen its research in the key areas of decarbonization, medicine and health, and environment and food, to tackle society’s most pressing issues.

Igusa is known for its unique scent that is said to have health benefits, but such claims lacked scientific evidence. Professor Kuniyoshi Shimizu from Kyushu University and his research team used EEG to monitor the brainwaves of participants while they sat on Igusa mats and completed a series of tasks. They found that when participants used Igusa mats, their brain activity showed patterns associated with increased concentration and engagement.

Credit

Yousuke Konno

Journal

Scientific Reports

DOI

10.1038/s41598-026-47520-8 

Method of Research

Experimental study

Subject of Research

People

Article Title

Stress resilience and engagement enhancement under the usage of Igusa (Juncus effusus L. var. decipiens Buchen.) mat: a crossover study

Article Publication Date

8-Sep-2026