This glossary has been designed to provide definitions that take account of different disciplinary and policy traditions and to consider the aspects of housing that provide scope for possible concerted research and action.
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Every little habitation within the great foul nest of one high building—that is to say, the room or rooms within every door that opened on the general staircase—left its own heap of refuse on its own landing, besides flinging other refuse from its own windows. The uncontrollable and hopeless mass of decomposition so engendered, would have polluted the air, even if poverty and deprivation had not loaded it with their intangible impurities; the two bad sources combined made it almost insupportable. (Charles Dickens)1
Any common sense evaluation will tell us that causation in part goes from poor housing to bad moral, mental and physical health. (Gunnar Myrdal)2
We give shape to our buildings, and they in turn shape us. (Winston Churchill in a 1943 speech to the House of Commons).
In the 19th century, public health initiatives that focused on housing did so because of the terrifying rates of infectious diseases and the common concern that these were concentrated in tenement buildings, which were poorly constructed, rack-rented, and did not allow air and light to circulate. The miasma theory proposed that the resultant fetid, malodorous air led to diseases like malaria (“bad air”) or through fermentation to zoonotic diseases and that these were the cause of sickness.3 These views only needed minor adjustment to encompass the later biological theory that it was the lurking bacteria that caused illness. Underlying these theories of causation was a moral view that what the feckless poor needed most to improve their housing and health was hygiene; they needed to be taught to clean their houses better and not to crowd together.
A few writers of the time adopted more radical views of the health consequences of housing. In the first clear case of multilevel analysis, Friedrich Engels used both mortality and municipal records to calculate the ratio of the living to the dead by categorising people not only by the ranking of the individual houses, from best to worst in the street, but also by the class of the street they lived in. The survival ratio was highest among those living in the best houses in the best streets.4
These 19th century aetiological theories have their 21st century counterparts. There are a number of aspects of housing that are understood to have a direct impact on health: the structure of housing; internal conditions such as damp, cold, and indoor contamination; and the behaviour of the occupants.5 Indirect housing effects related to housing tenure, including wealth impacts, and neighbourhood effects are seen as increasingly important.
Housing as a neglected site for public health action has been identified in a number of recent national reports.6–8 These reports highlight that indoor and outdoor housing conditions, as well as the material and social aspects of housing, and local neighbourhoods have an impact on the health of occupants. Moreover, systematic improvements in housing can improve health and reduce inequalities in health.
Housing and health research draws on research from a large number of disciplinary fields. This glossary has been designed to provide definitions that take account of different disciplinary and policy traditions and to consider the aspects of housing that provide scope for possible concerted research and action.
THE PHYSICAL STRUCTURE OF HOUSING
The physical structure of housing is an important part of the built environment. It encompasses both building materials and design, both of which can affect health. Examples of construction material impacts are: formaldehyde emissions from fibre-board materials; the release of asbestos from textured ceilings; and fibres from glass insulation material, which are all hazardous for human health. Particular designs create distinct problems of structural integrity, such as the apartments constructed from concrete, with inadequate steel reinforcing, in the former communist countries of Eastern Europe. Other design health effects include inadequate ventilation, and damp and mould.
The indoor environment refers to the quality of air inside the dwelling—which can be contaminated from a number of different sources, principally from building materials; side effects of heating; moulds and environmental tobacco smoke.9 In dwellings located besides busy roads and intersections, outdoor air contaminants from motor vehicle exhaust can pollute the indoors by being sucked in through windows or air conditioning systems. Contaminants from work and waste sites can be tramped inside on footwear. All these factors may influence the development of disease, through inhalation or ingestion. In some areas radon is also a major problem.10
Indoor heating is a major contributor to the quality of the indoor environment by raising the indoor temperature and, in the case of open fires and unflued gas appliances, releasing particulates, which irritate the airways and may suppress immune functioning.11 The burning of fossil fuels in gas cookers and un-flued gas heaters generates nitrogen dioxide and sulphur dioxide. As a result of incomplete combustion a number of other harmful contaminants are produced (hydrocarbons, carbon monoxide and particulate matter from inorganic matter in the fuel). Liquid petroleum gas or natural gas is generally perceived to be cleaner, but the by-products listed above can still be produced from incomplete combustion of these fuels. Environmental tobacco smoke from occupants’ cigarettes also produces harmful particulates.
Exposure to nitrogen dioxide inflames airways and presents a small but significant excess risk to vulnerable populations, especially children.12 Several researchers have noted a connection between gas cooking and respiratory illness in children.13–15 There is evidence that exposure to nitrogen dioxide in the week before the start of a respiratory viral infection, and at levels within current UK standards, is associated with an increase in the severity of resulting asthma.16
Increased blood lead concentrations in children, which affect their kidneys, reproductive organs, nervous system, and cognitive functioning have been linked to the ingestion of flaking lead paint in poorly maintained housing.17–20 Lead contaminated water from lead pipes is the other main source of lead intake in older homes.21 Recognition and regulation have led to an abatement of this problem, so that blood lead concentrations in children have declined dramatically,22 although there are still areas where children are at high risk.23
DAMP AND MOULD
Dampness in houses can be caused by the location of the house, structural defects in the house construction or maintenance, and the behaviour of the occupants, such as not airing the house by opening windows or using extractor fans during showering and cooking. Un-flued gas appliances also release water vapour that can increase the relative humidity in the house and lead to excess moisture in the building.24–28 Both subjective and objective measures of dampness in houses are used in research, and criteria are being established for evaluating observations in relation to exposure and adverse health effects, but it can be assumed that an estimate of the size of moisture damage is a reasonable surrogate for the exposure.29 Damp housing is clearly related to respiratory conditions in both adults and children.25,30–33
Mould is more likely to grow in damp houses and is usually measured by the size of the visible mould patches, or the mass of active colonies.34 A mouldy smell is a good indication of mould activity. Mould and fungi have been shown to have a small, but significant respiratory effect on children.35–40 There is a dose-dependent risk increase of visible mould for respiratory infections, lower respiratory symptoms,29 and asthma.33 There have also been isolated cases of mycotoxins producing haemorrhagic effect in children.41 Other biological products are β glucins and endotoxins.42–44 It is not yet clearly known which micro-organisms, among the many species infecting moisture damaged materials in the home, are most important for causing ill health and disease.45 Dust mites, which are the major producers of domestic allergens that exacerbate asthma, also thrive in damp housing.46–48
COLD AND SEASONAL DIFFERENCES
The temperature of the indoor environment affects the health of occupants. The WHO recommends that indoor house temperatures be no lower than 18° and 20° for the very old and very young.49 There is strong evidence that there is a narrow comfort zone for humans with mortality rates lower on days in which the average temperatures range between 15° to 25° and rising progressively as the ambient temperature becomes hotter or colder. Below these moderate temperatures there is some evidence that cold is a risk factor in increasing asthma severity and COPD and may also delay recovery after discharge from hospital.50–56
Seasonal differences in temperatures have a greater impact on avoidable mortality in winter in temperate countries than in colder countries, where houses are more thermally efficient and outdoor clothing is worn more systematically.57–61 In Great Britain, for example, it is estimated that 40 000 extra winter deaths occur each year because of housing and deprivation.59 In Great Britain an “inverse housing law” has been shown—those areas where climate is colder tend to be those where housing is worse. This maldistribution of good housing creates an additional environmental risk for those people living in colder areas for long periods of time and is associated with poorer respiratory health and diastolic hypertension.62,63 More equal socioeconomic development61 and the improvement of the thermal standards of housing have both been demonstrated to be effective preventative interventions to curb excess deaths.60
Fuel poverty, the inability to heat the indoor environment to healthy levels, is likely to be a consequence of low income and poorly constructed housing. It is generally the poor who have to pay the most to keep warm in relation to income, but who are least able to improve the energy efficiency of their dwellings. Fuel poverty and keeping warm is a particular problem among the elderly population.54,64
Crowding in households refers to the number of people per room and is measured in a number of different ways, from simple measures of the number of people per bedroom to measures, such as the Canadian Overcrowding Index, with underlying normative expectations of social standards.65
Crowding has long been known to increase the risk of infectious diseases, such as meningoccocal disease,66 tuberculosis,67 and hepatitis B,68 but it also has an impact on mental health69 and seems to be a contributor at an ecological level to premature mortality.70
Excessive noise in overcrowded houses and from neighbouring houses and traffic is a common cause of sleep disruption, which can lead to impaired concentration and irritability.5
MULTIPLE HOUSING DEPRIVATION
Multiple housing deprivation refers to the experience of poor housing over the course of a lifetime. Poor housing conditions in infancy, childhood, and adulthood such as overcrowding and damp, cold dwellings, have a cumulative detrimental effect on physical and mental health. Multiple housing deprivation seems to pose health risks of similar proportions to smoking and, on average, greater than that posed by excessive alcohol consumption.72
Children seem to be particularly vulnerable to prolonged exposure to poor housing.73,74 A number of adult diseases, such as Helicobacter pylori, have been traced back to exposure to crowding in childhood.75 Associations between poorer housing conditions in childhood and mortality from common diseases in adulthood are not strong, but are distinguishable from other aspects of social and economic deprivation.73
HOUSING CONDITION SURVEYS
A housing condition survey is a systematic survey of the physical condition of a dwelling, which identifies remediable hazards that otherwise have a negative impact on health and wellbeing. Houses are usually categorised according to fitness standards by environmental health officers or building inspectors so that local authorities can monitor and enforce regulatory standards to promote acceptable healthy housing.76 For example, the 1996 English House Condition Survey showed that that 1 522 000 UK dwellings did not meet the required fitness standards.77
Tenure is the legal conditions under which people live in their dwellings. Homes can be rented or owner occupied. If they are rented they can be rented from a private or public landlord. If homes are owner occupied, they may be owned with or without a mortgage, but, unlike rental properties, they can provide some financial benefits. One key advantage for many home buyers is that paying off a mortgage is a regular, “forced” form of saving, which yields security in later years.
Those who own their own home, with or without a mortgage, are likely to be in better health than those who rent their house, either from private or public landlords. There is a strong relation between rental housing tenure and higher death rates even within social classes. Several British studies have shown more variation in mortality between owners and tenants within occupational social class groups than between social classes within tenure classes. These relations are also related to self perceived health, rates of long term illness, and general practitioner consultation rates.78,79
While home ownership may generate a degree of security and control, particularly in countries where such behaviour is financially rewarded through tax assistance, it may not always be health promoting. Those households that fall behind on their mortgage payments may suffer increased insecurity and poorer mental health.80
Social housing is subsidised public sector housing that is provided to tenants by local, state, or national governments or not for profit trusts. Housing is usually allocated according to a social allocation formula that takes account of the prospective tenants’ health and social circumstances. The rent may be determined as a proportion of the household income, in which case tenants are likely to have more disposable household income. Social housing can also be called affordable housing, council housing, or state housing. In some countries, housing subsidies are provided by welfare payments or vouchers as a way of offering those on low incomes greater choice of whether to rent privately or publicly, or become owner occupiers.81
The expansion of social housing as part of state welfare policies was thought to have weakened the link between housing and health. However, area effects remain whereby even in the same city, there are “good” and “bad” estates. In the good estates the health of the tenants is measurably better.82,83 This may be the result of health selection, whereby the social allocation system filters people with poorer health into certain estates, or it may be that the reputation of certain areas means that people become less attached to these communities. This can lead to more residential mobility, which further weakens these areas’ social structures and organisations.84 The recent sale of better quality social housing under neo-liberal governments may have reduced fiscal burdens, but has led in some countries to a further concentration of tenants with low incomes and poorer health in identifiably socioeconomically deprived areas.85
Sheltered housing is subsidised, social housing that is provided to tenants with serious, chronic health problems or disabilities. Those with chronic mental health problems are particularly vulnerable in the private rental housing market and have been shown to benefit from sheltered housing.86 Tenants are monitored by case workers and are provided with the necessary social supports and health services.
Half way housing is transitional sheltered housing that is provided by social agencies for people leaving closed institutions such as mental hospitals or prisons, who otherwise would be likely to face difficulties in budgeting to pay full housing costs, or may be discriminated against in the private rental housing market.
HOUSING RELATED INJURIES
Houses can have a number of potential hazards inside, such as stairwells and loose carpets,87,88 and outside such as driveways.89 Fires are a major cause of mortality, particularly among poorer people who because of their social and economic circumstances are more likely to smoke.90–93
Housing discrimination refers to the racism that some groups such as indigenous people, migrants, and ethnic minorities are more likely to suffer personally from private landlords if they are renting, and from institutional lenders if they are seeking a mortgage.94,95 People from ethnic minorities with disability are more likely to suffer double discrimination.96
Housing is the largest capital asset many families own and thus can be used to provide financial flexibility, for example, as collateral against a personal loan. Housing wealth is the net asset value of an owner occupied dwelling calculated as the market value, minus the mortgage debt. Housing costs are usually the largest item of household expenditure. To adjust for this, disposable income is sometimes calculated after housing costs have been accounted for.97,98 When interest rates rise, households with mortgages can face a decline in after-housing disposable income.
Older people are more likely to have mortgage free homes, but may not have the income to maintain them.99 However, there are various reverse mortgage or equity schemes that are designed to enable older people to trade their equity in their house for regular income during their lifetime, although these have a high potential for coercion.
HOUSING AS PSYCHOSOCIAL SPACE
Housing is a private space with a public face, which can be seen as a symbolic extension of self. Housing is both a material asset and a psychosocial symbol of achieved status. It affects how people see themselves and are seen by others.100 Homes provide a secure space free from outside surveillance.101 Expectations and aspirations are conditioned by experience so that poor housing and deprived neighbourhoods may lead to pessimism, passivity, chronic stress, and a general state of dissatisfaction.102 If housing is of a relatively low standard, young people may want to distance themselves from the indoors and spend more time outside their home with their peers than with their families, which can dilute the impact of parenting, educational achievements, and the development of social norms.
IMPACTS OF HOUSING ON MENTAL HEALTH
Housing has a moderately strong effect on the mental health of the occupants, particularly women, who through their child rearing roles spend more time at home on average than men.69,103–108 Some designs of housing such as high rise housing often cause undue problems for older people and women, carrying shopping and small children, and make it more difficult for parents to supervise their children playing outside.109 There is also a perception that high rise apartments are less safe from crime110 and housing height is associated with decreased levels of mental health.111
There is a demonstrated cumulative impact of poor housing on mental health. For example, women in damp housing are more likely than men to experience emotional upsets because of overcrowding leading to disturbed sleep and on-going frustration from attempts to get repairs made, or failing that, rehousing, and in the meantime to keep the dwelling clean.112
Housing is a readily available setting for a number of public health interventions, but there is a lack of research results from intervention studies alone to support improved housing as a robust means to improve health.113,114 Insulating existing homes, providing effective safe heaters, and where necessary subsidised power, has been shown theoretically115 and in practice, to increase older people’s health and wellbeing113,116–121 and the health of children with asthma.122 In some cases the intervention prevented only further deterioration in health.120 The construction of new “passive” houses that are well insulated, have no active heating or cooling systems and use passive solar energy even in winter time, costs around 10% more but reduces energy running costs by a factor of 10 over the building lifetime.123 Such sustainable housing can increase the disposable income of the households and help to reduce inequalities.
Housing renewal is often carried out on sub-standard housing in socioeconomically deprived neighbourhoods, although it is likely to be less discriminating than selecting individual houses through housing condition surveys.59 Several before and after studies have shown that the mental health of tenants has improved after housing renewal or community regeneration,103,120,124 although some have reported adverse effects on general health after rehousing.106,125 Preliminary results of experimental relocation of families from areas of deprivation to improved housing in middle income areas have shown social and health gains126 and in another study, when the shift was to private housing, an improvement in mental health.127
The social and physical characteristics of the area surrounding houses are important for maintaining the good health of the occupants. Following the evidence that improving housing alone is insufficient to greatly improve the health of occupants, the focus has shifted to the health of the community and the local geographical neighbourhood. Neighbourhoods have a small but consistent impact on health status.128 Various omnibus measures of area based deprivation have been developed to rank the social and economic deprivation of neighbourhoods. Some are census based, some rely on municipal or school records.129,130 Some are based on systematic videotapes of street life and have been used to develop concepts such as collective efficacy and structural constraints in order to explore different neighbourhoods’ shared expectations for the social control of public space.131 Systematic observational studies have also shown that both place and people, both the context and the composition of neighbourhoods, are important in determining health.132
Multilevel analyses using area based measures, and increasingly using geo-coding, have shown that neighbourhood effects have a small, but significant impact on mortality and premature mortality,133–136 self reported health status,137 diseases such as gonorrhoea,138 as well as being risk factors for morbidity such as low birth weight.139 Aspects of neighbourhoods that have been identified as having an impact on health are: the presence or absence of local amenities, such as parks and sports facilities; “incivilities” such as the presence of graffiti, boarded up houses, garbage accumulation, abandoned cars and broken windows, and the signalling effect of these physical features that no one cares102; the perception of neighbourhoods as “safe” and under effective informal social controls100,107,110,138; and the number of local organisations.140,141
Others have postulated that neighbourhood conditions directly influence habits of privacy, child rearing, house keeping, and study, which can have an indirect effect on health.142
HOUSING AND NEIGHBOURHOOD ATTACHMENT
Families who live for a long time in a particular house can be categorised as attached to their house and local community and contributing to residential stability. Neighbourhood attachment is likely to have benefits for the health of the family and the stability of the neighbourhood. Neighbourhood stability in childhood is associated with better self reported health in mid-life, but as this stability is linked to family stability, the effects are difficult to disentangle.143
Residential stability refers to the social reproduction of neighbourhood residential structures, when typically population gains offset losses and home values appreciate.131 When longstanding families and households leave a neighbourhood, there is the possibility of destabilising social norms through the disruption of social networks. However, the destabilising effects of high levels of mobility are likely to have differential effects on different groups, depending on their social position and life stage and the material, social, and cultural resources from which they can draw. Many impoverished neighbourhoods have a high level of residential stability, yet poorer health. However, if the location, such as an inner city suburb becomes desirable and “gentrification” occurs, the in-migration of affluent households to poorer neighbourhoods can improve the health status of a neighbourhood simply through compositional changes.
Moving can be a normal part of family formation or a planned sign of upward mobility, but it can also reflect desperation and a downward spiral in health and welfare.144 This is one of the areas where qualitative research is able to illuminate the interaction between the increasing complexity of family life and residential mobility.145 The ability to move houses is related to the distribution of wealth and income in a population and the availability of social housing. Economic cycles and the local housing market are an integral part of this process.97
FUTURE HOUSING RESEARCH DIRECTIONS
Households, houses, and neighbourhoods are nested in such a way that the analytical tools of multilevel modelling can ideally illuminate their interrelation. However, the guidance of plausible theoretical models is an essential prerequisite for such analyses, if the field of housing and health research is to conceptually advance. Such models should progressively take account of the indoor built environment, as well as social and ethnic relations and the formal and informal rules that govern them. Both the direct and indirect effects of housing are also important, particularly the differential impact on age groups. The long term impacts of housing conditions need to be considered more in longitudinal studies.
Houses and neighbourhoods are a very practical setting for public health action and by their nature combine both private and public interests. Housing studies are more likely to attract broad public, policy and political support than most other settings. Housing policy interventions provide opportunities for natural experimental studies that can provide some fruitful answers to the key public health question of how we can reduce social and economic determinants of health inequalities. However, current interventions are limited by their scope and their narrow definitions of housing and health. It is hoped that this glossary highlights useful terms of reference, which will contribute to a broader environmental approach to improving health.
Comments by Ralph Chapman and the anonymous reviewers were much appreciated.
Funding: The Health Research Council of New Zealand funds the Housing and Health Research Programme.
Conflicts of interest: none declared
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