World-first NZ study links rheumatic fever to overcrowding

A world-first study has uncovered the strongest evidence yet that over-crowded homes raise the risk of acute rheumatic fever. Photo / Doug Sherring

A world-first study has uncovered the strongest evidence yet that over-crowded homes raise the risk of acute rheumatic fever – a serious illness that continues to affect Māori and Pacific children.

As well, Otago University epidemiologist Professor Michael Baker and colleagues have linked household overcrowding to streptococcal infections of the skin.

Their studies, published today in the international medical journal The Lancet Regional Health – Western Pacific, similarly found both illnesses were also associated with barriers to accessing primary health care, and with a family history of rheumatic fever and rheumatic heart disease.

One of the studies, focused on rheumatic fever and drawing on data from 124 cases, also pinpointed other risk factors including grandparents of any Māori or Pacific ethnicity; high intake of sugar-sweetened beverages; and self-reported skin infections and sore throats.

The other study, which included data from 733 children and focused on strep skin, also found children with grandparents of any Māori or Pacific ethnicity were at higher risk, as were those with eczema.

Baker described the findings as a major step forward.

"Finding a strong association between skin infection and rheumatic fever adds to evidence from other research conducted by our group about the importance of strep skin in triggering this disease," he said.

"These results suggest that treating skin infections in young children may provide a way of preventing them developing rheumatic fever.

"Our findings also reinforce the central role that good quality, uncrowded housing has in protecting children when they are vulnerable to rheumatic fever and other infectious diseases.

"It is also a reminder of the importance of having good access to primary health care."

Associate Professor Jason Gurney, who had a leading role in the rheumatic fever risk factors study, also emphasised the importance of the research findings.

"Rheumatic fever is an important example of the stark inequities that exist in terms of health outcomes in New Zealand," he said.

"Rates of rheumatic fever are around 20 times higher for Māori and 44 times higher for Pacific peoples than for non-Māori and non-Pacific peoples."

Gurney said it was vital the new Māori Health Authority, Public Health Agency and Health New Zealand acted on the findings as a high priority.

"It is also crucial that we look further upstream at the social determinants of this disease and continue to address inequities in access to things like high-quality, healthy housing and primary care."

Dr Julie Bennett, who took a leading role in the strep infection risk factors study, said the research provides a "path forward" to apply the broad findings and to test specific interventions that were highlighted in the research.

"The findings from these two studies and other related research suggest that skin infection is a key target for better treatment," she said.

"It would be useful to conduct suitable trials to see how better access to effective treatment of skin infections could be delivered most effectively and how this could lower the subsequent risk of rheumatic fever.

"Any interventions will need to be co-designed with Māori and Pacific peoples."

Rheumatic fever

• Rheumatic fever is an inflammatory reaction to group A Streptococcus bacterial infection of the throat and skin.

• One or more attacks of rheumatic fever can cause permanent damage to heart valves resulting in rheumatic heart disease, which may require major surgery and can result in a lower quality of life and premature death.

• The indigenous and Pacific populations of 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 annually.