Effect of insulating existing houses on health inequality: cluster randomised study in the community
BMJ 2007; 334 doi: https://doi.org/10.1136/bmj.39070.573032.80 (Published 01 March 2007) Cite this as: BMJ 2007;334:460
All rapid responses
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
Competing interests: No competing interests
Dear Editor
Howden Chapman et al(1) report significant improvement in perceived
health after insulation of homes in Otago New Zealand. What is not clear
is whether this improvement was caused by objectively measured increase in
indoor temperature and decrease in humidity, following insulation, or
whether it reflects psychological benefits of participation in this kind
of community intervention.
The associated editorial by Thomson and Petticrew(2) reports that
only 30% of participants in the intervention group received the full
insulation package, although Howden-Chapman’s previous paper(3) makes it
clear that almost all homes had at least ceiling insulation. Temperature
and humidity differences between the intervention and control houses were
very small, less than 1C in bedrooms (0.8C) and less than 3% difference in
humidity. Self reported change in health was large but was not confirmed
by data collected from GP records.
Curiously, this study may demonstrate that analysis by intention to
treat is not always the most rigorous method of evaluating a study’s
result. It would be reassuring to see a subanalysis within the intended
intervention group comparing homes which received the insulation package
versus those which did not, and showing that there was a dose response
effect on temperature, humidity and SF-36 change associated with actually
receiving insulation. Without this we cannot be confident that the health
effect reported was indeed due to the energy efficiency measures evaluated
in the study, and that health effects are mediated by temperature change.
We are sure that the authors can provide such a subanalysis, which
would answer these questions. It would be of great interest if this could
now be done.
Yours sincerely
Liesl M Osman
Senior Research Fellow, Department of Medicine and
Therapeutics, University of Aberdeen.
Graham Douglas
Consultant Chest Physician, Aberdeen Royal Infirmary.
Reference List
1. Howden-Chapman P, Matheson A, Crane J, Viggers H, Cunningham M,
Blakely T et al. Effect of insulating existing houses on health
inequality: cluster randomised study in the community. BMJ 2007;334:460.
2. Thomson H,.Petticrew M. Housing and health. BMJ 2007;334:434-5.
3. Howden-Chapman P, Crane J, Matheson A, Viggers H, Cunningham M,
Blakely T et al. Retrofitting houses with insulation to reduce health
inequalities: aims and methods of a clustered, randomised community-based
trial. Soc.Sci.Med. 2005;61:2600-10.
Competing interests:
None declared
Competing interests: No competing interests
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
Competing interests: No competing interests
As a former EHO that previously carried out housing inspections, I
read this research article with interest. The last English House Condition
Survey (EHCS)(1) estimating that 29% of our housing stock remains below
the ‘decent living’ standard, largely on the basis of thermal comfort.
Therefore, the Howden-Chapman et al study(2)highlighted an important
potential health concern.
The EHCS states that many of the occupants of these substandard
dwellings are already amongst the most deprived and vulnerable within the
population. Howden-Chapman's study findings would suggest that some basic
improvements in housing standards could have a disproportionately
beneficial health effect amongst these hard to reach populations.
Whilst, not suggesting that the medical profession should now
consider themselves responsible for an improvement in housing standards, I
do believe that an opportunity exists to develop a more coordinated
approach to tackling this potential source of ill health.
Last year the Housing Fitness Standard set out in the Housing Act
1985(3) was replaced by the Housing Health & Safety Rating System(4).
A key change contained within the new system relates to its ability to
require remedial action to be taken on the basis of the level of ‘health
risk’ posed to occupants of the premises, rather then particular defects
in the physical properties of the building.
It is in the identification of potential ‘health risks’ that a
combination of research such as Howden-Chapman et al and local medical
practitioners health knowledge can play a role in the improvement of local
housing standards. Addressing EHOs about the new rating system, Professor
David Ormandy, one of the architects of the system, said:
“Remember your PCTs are supposed to be looking at the health impacts
in housing. This local information should be informing the decent home
standard and programmes………Also, we should be able to demonstrate a few
years down the road that this work on housing has had an effect that is
beneficial to the health service”(5).
Consequently, issues of blinding and the reliability of self reported
responses aside, I welcome the publication of this paper in this Journal.
1)Department for Communities and Local Government, English House
Condition Survey 2004 Annual Report, HMSO, London, 2006
2)Howden-Chapman P, Matheson A et al. Effect of insulating existing
houses on health inequality: cluster randomised study in the community BMJ
2007. BMJ 2007; 334: 460
3) Housing Act 1985
4) The Housing Health and Safety Rating System (England) Regulations
2005, HMSO, London
5) Spear S, New light on risk, Environmental Health Practitioner, May
2006; 24-25
Competing interests:
None declared
Competing interests: No competing interests
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
Competing interests: No competing interests
I want to congratulate Howden-Chapman et al for completing such a
large study looking at the effects of insulating houses on the health of
occupants.(1) It is interesting to see research confirming what often
seems logical. Although one of the measures (the SF36) does collect some
information on mental health, I could find no further discussion of this
in the article.
Being in the business of mental health, I decided to look at the
issue of mental health and housing myself. I was reassured to find that
the quality of housing also predicts mental health.(2) It seems that the
reporting of 'dampness' can cause psychological problems,(3) as well as
the location and type of dwelling.(4) Although standard methods of
psychiatric history-taking include details of the home and home
environment, they do not include detailed questioning of the level of
insulation, presence of dampness or the type of neighbourhood. Perhaps
such questioning can now be included in the new Specialist Trainiing
curriculum for psychiatry. Dear PMETB ....
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.)
2. Evans GW, Wells NM, Chan HY, Saltzman H. Housing quality and
mental health. Journal of Consulting and Clinical Psychology
2000;68(3):526-30 (June.)
3. Hopton JL, Hunt SM. Housing conditions and mental health in a
disadvantaged area in Scotland. Journal of Epidemiology and Community
Health 1996;50:56-61
4. McCarthy P, Byrne D, Harrison S, Keithley J. Housing type, housing
location and mental health. Social Psychiatry 1985;20:125-30
Competing interests:
The author lives in a house that is insulated, but has some dampness
Competing interests: No competing interests
Are houses in NZ without insulation owned by people of a lower
socioeconomic group?
Competing interests:
None declared
Competing interests: No competing interests
How the results of the study apply to the UK - Health inequality, statistical significance, and ‘real’ significance
Dear Editor,
Randomised control trials, which are higher up in the hierarchy of
evidence, are more difficult to do in a community setting and the authors’
efforts are commendable. The title of the study clearly attracts the
attention of anyone passionate of reducing health inequalities by tackling
the wider determinants such as housing. Though there is clearly an
improvement in self reported health outcomes in the intervention group,
the difference is not statistically significant in terms of objectively
measured health outcomes like use of primary care and hospital admissions
which denotes a possibility of responder bias. Also, it is unclear whether
insulating existing houses had any effect on health inequality in terms of
reduction in the health gap between different socio economic areas.
The study clearly indicates that insulating houses can increase the
mean bedroom temperature from 13.6oC to 14.2oC, i.e. a 0.6oC rise due to
insulation, which is statistically significant (P=0.04) due to a large
sample size1. The energy usage in insulated households were only 81% of
the control households (P=0.0006). According to the UK fuel poverty
strategy, the recommended minimum temperature levels that maintain health
in the living and other used rooms are 18oC and 16oC respectively2.
Therefore, though there is a statistically significant evidence that
insulating houses can increase the indoor temperature by 0.6oC, it alone
cannot achieve a desired level of temperature rise of 4-5oC to maintain
health. Perhaps we need to consider both heating our homes as well as
insulating them and not just insulate them to reduce the winter related
morbidity and mortality.
1. Howden-Chapman P et al. Effect of insulating houses on health
inequality: cluster randomised study in the community. BMJ 2007; 334:460
2. Department of Trade and Industry and Department for Environment, Food
and Rural Affairs. 2001. The UK Fuel Poverty Strategy. London:Department
of Trade and Industry and Department for Environment, Food and Rural
Affairs.
Competing interests:
None declared
Competing interests: No competing interests