Effect of insulating existing houses on health inequality: cluster randomised study in the community

We applaud BMJ’s recent focus on the importance of high-quality
housing to the maintenance of human health (1). Housing must be a focal
point in public health research and practice. In a large, New Zealand
based randomized controlled trial, Howden-Chapman et al (2) showed that
insulating homes improves health. Such research and related action is of
even greater importance in resource-poor countries, where much fewer
randomized trials have been conducted, but where poverty’s diseases,
especially those that are vector-borne, nonetheless thrive on rural
dwellers of thatched-roofed, mud-walled homes in disrepair.

The global poor seem to be well aware of such critical linkages, as
suggests our experience working as public health workers and clinicians
among a rural community in southeastern Liberia. Recent conversations
there suggest a strong community-wide perception that improved housing is
one step toward the avoidance of malaria. People who have been able to
improve their homes, for instance, through converting materials used to
construct their roofs from thatch to zinc, nearly universally perceived
fewer cases of malaria after the improvements than before.

The viewpoints of rural Liberians are well supported by a growing
body of evidence, which is well reviewed by Lindsay et al (3). Some
improvements are intuitive, such as window and door screens and the
modification of eves to prevent mosquitoes’ access to homes. Others are
less intuitive but just as effective. Research in Burkina Faso found that
children under five years of age had a greater than double the odds of
malaria infection if they lived under a mud roof than under a metal roof
(4). In Sri Lanka, improved housing was found to be a cost-effective
intervention that would pay for itself in health savings over a relatively
short period of time (5). Additionally, housing improvements have been
shown to be protective against other vector-borne diseases of the
developing world, including Chagas disease(6) and filariasis (7).

Policy makers should view housing improvements as a means to improve
the human condition, not only as it pertains to health, but also in terms
of the inherent right to live in safe and edifying conditions that promote
the flourishing of the human spirit (8,9). There is a synergy between
health, housing, and human dignity that must be taken as seriously by
policy makers and researchers as it already is by the world’s destitute
sick.

Sincerely,

John D. Kraemer
JD/MPH Candidate
Georgetown University Law Center /
Johns Hopkins Bloomberg School of Public Health
jkraemer@jhsph.edu

Rajesh R. Panjabi, MPH
University of North Carolina School of Medicine
panjabi@med.unc.edu

References

1. Thomson H, Petticrew, M. Housing and health. BMJ. 2007; 334: 434
-435.

2. Howden-Chapman P., Matheson A, Crane J, Viggers H, Cunningham M,
Blakely T, Cunningham C, Woodward A, Saville-Smith K, O’Dea D, Kennedy M,
Baker M, Waipara N, Chapman R, Davie G. Effect of insulating houses on
health inequality: cluster randomized study in the community. BMJ. 2007;
334: 460.

3. Lindsay SW, Emerson PM, Charlwood, JD. Reducing malaria by
mosquito-proofing houses. Trends Parasitol. 2003; 18: 510-514.

4. Ye Y, Hoshen M, Louis V, Seraphin S, Traore T, Sauerborn R.
Hosing conditions and Plasmodium falciparum infection: protective effect
of iron-sheet roofed houses. Malar J. 2006; 5: 8-14.

5. Gunawardena DM, Wickremasinghe AR, Muthuwatta L, Weersingha S,
Rajakaruna J, Senanayaka T, Kotta PK, Attanayake N, Carter R, Mendis KN.
Malaria risk factors in an endemic region of Sri Lanka, and the impact and
cost implications of risk factor-based interventions. Am J Trop Med Hyg.
1998; 58: 533-542.

6. Rojas de Arias A, Ferro EA, Ferreira ME, Simancas LC. Chagas
disease vector control through different intervention modalities in
endemic localities of Paraguay. Bull World Health Organ. 1999; 77: 331-
339.

7. Baruah K, Rai RN. The impact of housing structures on filarial
infection. Jpn J Infect Dis. 2000; 53: 107-110.

8. United Nations. Universal declaration of human rights, Article 25.
Geneva: UN, 1948.

9. United Nations. International Covenant on Economic Social and
Cultural Rights. Geneva: UN, 1976

Competing interests:
None declared

The Howden-Chapman et al study (1) looking at the effects of
insulating houses on health is an important milestone in the study of
housing and health, and we congratulate the authors on their achievement.
To this straightforward intervention we would note that multiple
intervention pathways in the housing area can have further benefits.

The Healthy Housing programme is a joint project between Housing New
Zealand Corporation (HNZC – the provider of publicly-funded housing), and
Counties Manukau, Auckland, and Northland District Health Boards (DHBs).
It targets localities with high health needs, low income, and with high
concentrations of HNZC properties. It aims to assist families with high
rates of hospital admissions for preventable infectious diseases.

HNZC staff work directly with health professionals to identify
families that are living in conditions that may affect their health, and
then an assessment is carried out to see what can be done. This can
include a range of things – from educating families about health risks and
putting them in touch with local health providers (an average of 3
referrals per household), to making the house dryer and warmer by
installing insulation, or in some cases making the house physically
bigger. Over 4000 homes have been assessed from the programme’s
instigation in 2001. While not designed as a randomised study,
evaluations have found improvements in self-rated health, self-esteem, use
of primary care and reductions in the use of secondary care; all
consistent with the present study.

Examining acute hospital admissions, we performed a case-
counterfactual study on 5357 residents of 1276 homes involved in the
Healthy Housing Programme in the Counties Manukau DHB area. Almost all
participants were of Pacific ethnicity, living in some of the most
deprived areas of New Zealand (all NZDep01 decile 10). We used a pre-
determined set of “housing-related” potentially avoidable hospitalisations
(HR-PAH). HR-PAH includes acute admission for respiratory infections,
tuberculosis, gastroenteritis, ear, nose and throat infections,
meningococcal meningitis, asthma and COPD. A person was included as a
case for each day they were living in a modified house in the period 2003-
2004. People living in houses prior to modification were the
counterfactual (control group), again if they were in the 2003-2004
period. Houses that were modified prior to 2003 only appear as a case,
houses modified after 2004 only appear as a counterfactual. Houses
modified in 2003-4 will appear in both case and counterfactual. People
living in the modified houses had a 37% lower rate of HR-PAH than the
counterfactual householders, 36/1000 persons/year as compared to 23. For
the group of houses analysed this amounted to preventing around 120 acute
admissions to hospital per year. The largest decrease was seen in
respiratory conditions, particularly in children. Households that had
had interventions to reduce overcrowding (eg additions of bedrooms) had a
slightly larger fall (OR 0.61, 95% CI 0.43-0.86) than those that had
insulation/ventilation modifications only (OR 0.68, 0.53-0.89).

It is possible to work across agencies to directly impact on the
living conditions of the most deprived segments of our society. Multiple
interventions can have additive effects. Of particular note in this group
of low-income tenants is the obvious pride they take in their renovated
dwelling, as evidenced by very low turnover rates and very low
damage/maintenance requirements. This improved self-esteem will impact on
many aspects of the families’ lives, well beyond the effects seen in the
health care sector.

1) Howden-Chapman P, Matheson A et al. Effect of insulating houses
on health inequality: cluster randomised study in the community. BMJ
2007;334:460 (3 March.)

Gary Jackson, Public Health Physician, CMDHB

Jude Woolston, Project Manager (Intersectoral), CMDHB

Alan Bernacchi: Project Manager, Healthy Housing Programme,
Housing New Zealand Corporation

Competing interests:
None declared

Dear Sir

The authors have provided a caring intervention to people whose lives
are deprived of such. This aspect of the intervention applies to the
inhabitants of both the 'treated' and the 'untreated' homes. However, I
was surprised that the 'untreated' homes were not subject to modification
with inactive insulation; this would have enabled a more blinded research
protocol.

In light of this study and the comments about mental health and
physical health being affected, I would add that the 'mental' aspects of a
physical brain and its attendant control and communications systems are
all developed and delivered as physically as every other organ system in
the body.

Further emphasis of the importance of these connections are provided
in today's review by the Royal Commission on Environmental Pollution.
Despite Black, Jarman and Wanless, our Government is still ignoring many,
if not most, of these issues and their impact on developing brain-minds,
as detailed in the bleak overview provided by the UniCEF Report of a
fortnight ago and emphasized by Dr Des Spence's Opinion piece in this same
issue of the BMJ.

Yours
Dr Chris Manning

Competing interests:
None declared