A significant association was observed between household crowding and access to primary health care, among other factors, and the development of acute rheumatic fever (ARF), according to study findings published in Lancet.
Researchers sought to identify risk factors for ARF and rheumatic heart disease (RHD) and conducted a population-based matched case-control study in New Zealand between 2013 and 2016. Control participants were randomized in a 3:1 ratio and matched to case participants by age, ethnicity, socioeconomic deprivation quintile, and region. When possible, control participants were also matched on sex (77.2%).
A total of 494 participants (65.3% men) were included in either the case group (n=124) or the control group (n=372), and nearly all patients in the case group were either Māori (41.9%) or Pacific (57.3%). Participants in the case group were aged less than 20 years, experienced their first episode of ARF within 4 weeks of hospitalization, and resided on the North Island of New Zealand.
All participants were interviewed in-person using a pretested questionnaire that assessed exposure status during the 4 weeks prior to illness or interview. Additional data were obtained from linked records. Exposure measures included dampness and mold in the home, cold in the home, limited hot water for bathing, barriers to primary health care access (ie, difficulty scheduling an appointment within 24 hours, appointment and prescription costs, and lack of transportation) and ARF health literacy. Structural household crowding was assessed using the American Crowding Index. Functional crowding was defined as sharing a sleeping room to stay warm.
There was a strong association between structural housing crowding (adjusted odds ratio [aOR], 6.04; 95% CI, 3.03-12.04) and structural crowding (aOR, 3.26; 95% CI, 1.78-5.97). Risk for ARF was also increased with exposure to cold (aOR, 1.99; 95% CI, 1.22-3.33), exposure to dampness and mold (aOR, 3.03; 95% CI, 1.88-4.92), and rental housing occupancy (aOR, 3.48; 95% CI, 1.81-6.70). Lack of hot water for bathing was also associated with ARF risk (aOR, 2.45; 95% CI, 1.29-4.74). Knowledge of ARF seemed to be a protective variable (aOR, 0.52; 95% CI, 0.28-0.95).
Multivariable analyses showed that risk for ARF was significantly associated with barriers to accessing primary health care (aOR, 2.07; 95% CI, 1.08-4.00), a family history of ARF or RHD (aOR, 4.97; 95% CI, 2.53-9.77), and having 4 grandparents of Māori or Pacific ethnicity (aOR, 5.79; 95% CI, 2.60-12.88).
Results from this study demonstrate the importance of suitable, well-maintained housing as key to prevent the incidence of ARF in countries where it remains endemic. Historically, ARF has been observed in disadvantaged people among all ethnic groups, internationally and in New Zealand, highlighting the importance of environmental ARF risk factors.
Limitations of the study included possible social desirability bias with regard to questions on risks for children, which may have resulted in differential reporting between cases and controls. New Zealand is a high-income country, and some findings may not be generalizable to low- and middle-income countries where most ARF cases occur. The temperate climate of New Zealand may have also influenced some housing factors such as coldness, dampness, and mold that are less likely to be found in more tropical climates.
The study authors concluded, “The study findings direct attention to the critical importance of household crowding, access to primary health care, and family history as likely causal factors in the development of ARF, which therefore should be the target of interventions to reduce highly inequitable ARF rates.”
Baker MG, Gurney J, Moreland NJ, et al. Risk factors for acute rheumatic fever: a case-control study. Lancet. Published online July 4, 2022. doi:10.1016/j.lanwpc.2022.100508