A study by the University of Otago in New Zealand has found the strongest evidence yet that household overcrowding is a major risk factor for acute rheumatic fever and streptococcal skin infection.
Their research is published in two accompanying articles in an international medical journal The Lancet Regional Health – Western Pacific.
Lead researcher Professor Michael Baker of the University of Otago, Wellington, says it’s the first time researchers have looked at risk factors for group A strep throat (sore throat) and skin (strep skin) infections, which can cause rheumatic fever.
Studies have shown that both rheumatic fever and strep skin were associated with barriers to accessing primary care and a family history of rheumatic fever and rheumatic heart disease, a serious condition that can develop if rheumatism is left untreated.
Professor Baker says identifying the key pathway that drives rheumatic fever risk is a big step forward.
“Finding a close link between skin infection and rheumatic fever complements the evidence from other studies conducted by our group on the importance of skin streptococci in triggering this disease. These results suggest that treating skin infections in young children may provide a way to prevent them from developing rheumatic fever.
“Our results confirm the central role of quality sparsely populated housing in protecting children during a period when they are vulnerable to rheumatic fever and other infectious diseases. It’s also a reminder of the importance of good access to primary care.”
One unexpected finding of the rheumatic fever risk factor study was that consumption of sugar-sweetened beverages was twice as common among rheumatic fever cases compared to healthy controls, even after adjusting for all other risk factors.
“There are several ways in which sweetened beverages may increase the risk of rheumatic fever. We are planning further studies to test some of these hypotheses. In the meantime, this is another reason for children to switch to healthy alternatives such as water or plain milk,” says the professor Baker.
Associate Professor Jason Gurney (Ngā Puhi), who has played a leading role in research into rheumatic fever risk factors, also highlighted the importance of the study’s findings.
“Rheumatic fever is an important example of the stark inequalities that exist in terms of health outcomes in New Zealand. The rate of rheumatic fever is approximately 20 times higher in Māori and 44 times higher in Pacific peoples than in non-Māori and non-Pacific peoples.
“It is vital that new health organisations, particularly the Māori Health Authority, the Public Health Agency and Health New Zealand, use these research findings as a high priority. It’s also critical that we look further downstream at the social determinants of this disease and continue to address inequities in access to things like high-quality, healthy housing and primary health care.”
Dr Julie Bennett, who took the lead role in research into risk factors for strep, says the study provides a way forward for Aotearoa New Zealand to apply the broad findings and test specific interventions highlighted in the study.
“The findings of these two studies and other related studies suggest that skin infection is a key target for better treatment. Appropriate trials would be useful to learn how better access to effective treatment for skin infections can be most effective and how this can reduce the subsequent risk of rheumatic fever. Any interventions must be developed in collaboration with Māori and Pacific peoples.”
Professor Jonathan Karapetis, director of the Telethon Institute in Perth, Western Australia, and professor at the University of Western Australia, is one of the world’s leading researchers on rheumatic fever and other streptococcal diseases. He describes the research as a breakthrough in the global fight against these diseases.
“This is by far the most rigorous study ever conducted to identify risk factors for rheumatic fever. The study of risk factors for strep throat and skin infections is a world first. Taken together, these studies provide a very strong foundation that can help guide our collaborative aim to eliminate rheumatic heart disease as a global health problem.’
Rheumatic fever is an inflammatory response of the throat and skin to a group A streptococcal bacterial infection. One or more attacks of rheumatic fever can lead to permanent damage to the heart valves, which can lead to rheumatic heart disease, which may require major surgery and can lead to reduced quality of life and premature death. Indigenous and Pacific populations in New Zealand and Australia have some of the highest rates of rheumatic heart disease in the world. In 2015, an estimated 34 million people were living with rheumatic heart disease, with approximately 233,000 deaths each year.
The Rheumatic Fever Risk Factors Study was funded by the New Zealand Rheumatic Fever Research Partnership (HRC) (with support from the New Zealand Ministry of Health, Te Puni Kōkiri, Cure Kids, the Heart Foundation and the HRC itself). The study of risk factors for streptococcal infection was funded by HRC.
The researchers would like to thank the many participants and their families for sharing their time and expertise to make this research possible, as well as the Māori and Pacific consultants, clinicians, health professionals, medical staff, support staff at the DHB, laboratory staff diagnostic laboratories and ESR and interviewers employed by CBG Health Research Limited.