Smoke exposure in early life and Rheumatic Heart Disease

david-phillipsDavid Phillips

Rheumatic Heart Disease (RHD) is caused by a bacterial (streptococcal) throat infection acquired in childhood.  Although this type of infection is common and widespread, a small proportion of children so affected go on to develop an inflammatory condition that leads to scarring and narrowing of the heart valves and, in time, heart failure. Early on in the course of the disease the joints may be affected – hence the term “rheumatic”.

Still an important disease
At one time Rheumatic Heart Disease was common throughout the UK, Europe and the US; it was the most important cause of heart disease among young adults in Victorian Britain and probably caused the death of Mozart.  Although rare now in most developed countries, it remains an important public health problem in many low and middle income countries. The disease is widespread in the Middle East and Asia, and the the poor indigenous populations of some wealthy countries, for example among Australian Aboriginees and New Zealand Maoris. It is particularly prevalent in sub-Saharan Africa, where it is one of the commonest causes of heart disease, typically affecting children or young adults. There it carries a grim prognosis because of the lack of specialised treatment.

A disease of poverty
The reason for the disappearance of the disease in the western world, which began well before the discovery of antibiotics, is not understood. It has been assumed to be due to better living conditions as rheumatic heart disease is known to be strongly linked with poverty – the Victorian physicians would often remark that the disease was a condition of their (poor) public patients but rarely seen in their wealthy, private patients.  Because the disease has not been perceived to be a priority, research into it has been greatly neglected.

Prevention a priority
The current approach to preventing RHD depends on the use of penicillin injections either to achieve primary prevention, by treating children presenting with bacterial sore throats, or on a secondary basis, to prevent disease progression in children who have already been identified as having the disease. Although some success has been achieved using the approach, for example in Costa Rica, the notorious under-resourcing of formal health systems and the lack of qualified medical staff in many poor countries hinder this approach and highlight the need for new ideas.

A connection with early exposure to air pollution?
Epidemiological studies in resource-poor countries are difficult and we have therefore used historical mortality data from the UK to investigate the disease. We were stuck by the close parallels between rheumatic heart disease and chronic bronchitis – areas of the country with high rates of chronic bronchitis also had high rates of RHD and both diseases were commonest in parts of the UK where infants had high rates of chest infection. Because chronic bronchitis and chest infection in infancy are now known now to be strongly linked with air pollution, we decided to investigate whether RHD might also be associated with air pollution.

Using old government records of domestic coal burnt between May 1951 and May 1952 (at a time when rationing was still in force), we found strong correlations between regional fuel consumption and regional mortality rates from rheumatic heart disease some 50-60 years later. Although there are many limitations to this data, the results suggested that early exposure to air pollution might increase the susceptibility to the disease. The idea is also supported by a body of experimental work which suggests that air pollution impairs immune function. Although there are a number of possibilities, domestic smoke exposure may simply increase the severity of streptococcal throat infections so increasing the likelihood of developing rheumatic heart disease.

From the UK to sub-Saharan Africadomestic-air-pollution
Domestic air pollution is the norm for many families living in sub-Saharan Africa. Cooking is typically carried out on open fires and the resulting smoke permeates throughout the house. Infants and young children may be heavily exposed especially in poor families who tend to use the smokiest fuels such as crop waste or dung. We think our results could help explain the persistence of rheumatic heart disease in the many parts of the world where domestic air pollution is still common. It may be that something as simple as better ventilation of people’s houses could prevent this terrible disease.

Read more:

Phillips DIW, Osmond C, Williams ML, Jones A. Air pollution in early life and adult mortality from chronic rheumatic heart disease. International Journal of Epidemiology 2016: doi: 10.1093/ije/dyw249.

Phillips DIW, Osmond C. Is susceptibility to chronic rheumatic heart disease determined in early infancy? An analysis of mortality in Britain during the 20th century. Global Cardiology Science and Practice 2014; 4: 464-72.

Carapetis JR, Beaton A, Cunningham MW, et al. Acute rheumatic fever and rheumatic heart disease. Nature reviews Disease primers 2016; 2: 15084.

David Phillips is Professor of metabolic and endocrine programming at the University of Southampton. His research now focuses on neglected non-communicable diseases in Ethiopia and other countries in sub-Saharan Africa.

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