PROTOCOL: Housing improvements for health and associated socio‐economic outcomes

Hundreds of studies have investigated the health of populations and their housing conditions, resulting in a body of evidence which displays strong associations between poor health and poor housing (Bonnefoy 2003; Fuller-Thomson 2000; Holmes 2000; Hopton 1996; Humfrey 1996; Hunt 1993; Macintyre 2003; Martin 1987; Peat 1998; Raw 1995; Raw 2001; Revie 1998; Wilkinson 1998; Wilkinson 1999). Despite this, there remains some ambiguity about the strength of evidence and also the nature of the link between poor housing and poor health (Dunn 2000; Howden-Chapman 2002; Thiele 2002). This may be largely explained by the inextricable links between poor housing and other determinants of poor health such as poverty and pre-existing poor health. For example, vulnerable groups such as the sick, the elderly, and the unemployed are among those most likely to live in poor housing and who also tend to spend long periods of time indoors exposed to potentially hazardous environments (BMA 2003). Poor housing conditions may comprise a number of factors and the prevalence and relevance of specific factors may vary according to context. For example, temperature control is related to health. in colder countries there is a need to provide adequate, affordable warmth while in warmer countries the emphasis may be on keeping occupants cool in hot summers. The aspects of poor housing which are most commonly linked to adverse health outcomes (Raw 2001) are detailed in Box 1 (UK data). Box 1. Most significant housing hazards associated with health effects * (Box 1a) plus type of health effects commonly linked to poor housing (Box 1b) Poor housing is both an indicator of poverty and a common target for interventions to improve public health and reduce health inequalities (Gauldie 1974). For example the WHO Knowledge Network on Urban Settings and the WHO Commission on the Social Determinants of Health have highlighted the need to create healthy housing and healthy neighbourhoods for future health (Kjellstrom 2007). Within public health more generally, housing policy is regularly cited as both a determinant of health and health inequalities (Shaw 2004; Thiele 2002) and a means by which inequalities may be tackled (Best 1999; Howden-Chapman 2002). Interventions to improve housing conditions may involve changes to the physical fabric of the housing, equipment and educational interventions to reduce exposure to hazards, in particular air pollutants and allergens, and to reduce domestic injury. This review will focus on interventions to improve the physical fabric of housing. These interventions vary and may comprise demolition of substandard slum housing and rehousing of occupants to new build housing with modern facilities; refurbishment of existing housing; remediation of damp or mould problems; provision, repair or upgrading of heating or energy efficiency measures such as insulation. The well-established associations between poor housing and poor health suggest that housing improvement may well be justified on health grounds alone. Interventions to upgrade the housing fabric typically involve substantial changes to housing and may affect, intentionally or not, exposure to a range of potential hazards. For example, energy efficiency measures may result in improved warmth, elimination or containment of mould or damp, and improved air quality as well as reduced fuel costs. It is hypothesised that reduction in exposure to housing conditions associated with poor health will result in health improvement, although the timescale for the impact on health is not clear and may not be immediate. In addition, associated socio-economic factors may mediate between the potential for health improvement and housing improvement. Thus improved housing conditions may be regarded as an intervention which can tackle the complex dynamic between poverty and poor health. Much of the existing research investigating the links between housing and health has been cross-sectional. These studies have often demonstrated strong independent associations between housing conditions and health; however the lack of control for confounders means that their results remain open to debate and interpretation (Wilkinson 1999). In addition, reports of links between poor housing, deprivation and ill health may have only a limited role in informing specific policy decisions around the nature of investment or housing improvement required to improve health (Maclennan 1999; Thunhurst 1993). Experimental studies of the health impacts of housing would provide stronger evidence. However, the experimental approach to housing research has been criticised for being reductionist and ignoring the multi-factorial nature of causality in housing, deprivation and health (Hunt 1993). In addition to this objection there are substantial methodological, pragmatic and ethical obstacles to the conduct of trials in this field. The key issues are outlined below. Principles of social justice dictate that it would be unethical to withhold an available benefit, such as improved housing, from those deemed eligible simply for the purposes of research. Randomisation may only be justifiable where there is a natural delay or waiting list in distributing the housing improvement to eligible participants (Thomson 2004). Such studies are rare. It is most often impossible to blind participants or assessors to the allocation to intervention group or control group, resulting in high levels of recall bias (Rothman 1998). In cases where randomisation is not possible, identifying a suitable control group which is similar both socio-demographically and in terms of eligibility for a housing improvement is difficult. There may be a time delay between exposure to a housing hazard and emergence of the health effect. Furthermore, housing improvements are often accompanied by wider neighbourhood improvements and it is therefore difficult to attribute changes in outcomes to housing improvement alone. Although experimental and quasi-experimental trials of housing improvement may still be possible, the issues raised above may partly explain why trials of housing improvements, randomised or not, have rarely been conducted. In light of these problems and the current lack of data from randomised trials, it would appear that data from small uncontrolled studies may be considered valuable to establish the nature and extent of possible health impacts following housing improvement. A number of reviews have examined the strength of association between housing specific hazards and health (Institute of Medicine 2004; Peat 1998; Rauh 2008; Raw 2001; Revie 1998; Wilkinson 1999). A recent review of reviews identified nine systematic reviews of housing related interventions which had examined impacts on health outcomes and health inequalities (Bambra 2008; Bambra 2010). Three of these reviews were of measures (including equipment and exercise regimes) to reduce falls at home amongst the elderly (Chang 2004; Gillespie 2003; McClure 2005); two reviews involved community and housing based interventions to reduce community and domestic injury (Nilsen 2004) and firearm injury (Hahn 2005); two reviews were of rental assistance programmes (Acevedo-Garcia 2004; Anderson 2003); one review examined UK investment in area based renewal, some of which included housing-led renewal (Thomson 2006); and one review assessed the health impacts of physical improvements to the housing fabric (Thomson 2001). These latter two reviews (Thomson 2001; Thomson 2006) were conducted by the authors of this protocol. Other systematic reviews of housing interventions for health which we have identified, including Cochrane reviews, have focussed on equipment or behavioural interventions, or both, to reduce exposure to allergens amongst asthmatics (Gøtzsche 2008) and to reduce domestic injury and fires (DiGuiseppi 2000; Kendrick 2007Lyons 2006). Two further reviews conducted in the USA have been identified (Jacobs 2009; Saegert 2003). Neither of these reviews were systematic reviews, and they focussed on interventions aimed at minimising exposure to specific hazards, for example pest management, cleaning treatments, dehumidifiers and behavioural interventions to reduce domestic injury. In addition, both these reviews were limited to US literature. The 2001 review by Thomson et al is the only international systematic review of improvements to the physical fabric of housing which has been identified to date (Thomson 2001). The review, conducted in 2000, included all quantitative studies of housing improvement, of any design, which took a measure of health, illness or wellbeing; 18 completed studies and 14 ongoing studies were identified. Of the 18 completed studies, eight were identified from electronic databases including databases of unpublished literature. The remaining 10 studies were identified through personal communication, conference attendance and handsearching bibliographies of books. Of these 10 studies, eight were conducted in the UK and two in the USA (Thomson 2002). Although this distribution between studies in the UK and the USA reflects the distribution of study locations identified through the electronic databases, it is possible that unpublished studies from beyond the UK were missed and this may have introduced some bias into the review. Many of the ongoing studies identified are now due for completion and an update to this review is required. Extra efforts to identify unpublished studies carried out beyond the UK will be made. A Cochrane review of remediation of damp and mould to buildings, including housing, is also currently underway. To assess the health and social impacts on residents following improvements to the physical fabric of housing. Prospective, retrospective, controlled, uncontrolled, randomised (including cluster randomised trials) and non-randomised studies of the health and social effects of housing improvements will be included in the review. Cross-sectional studies that do not investigate the effects of housing improvement will not be included, that is cross-sectional surveys reporting associations between housing conditions and health. Intervention studies reporting both quantitative and qualitative data will be reported in the review. The study designs and names used to describe study designs are defined in Appendix 1. The review will not exclude any participants on the basis of family type, socio-economic status or other equity indicators such as race or ethnicity, occupation, education or religion. Studies from any region of the world and from both industrialised and non-industrialised countries will be included. Outcomes for both adults and children will be included in the review. Included participants will be in receipt of a discrete programme of rehousing or housing improvement. Where households experience a change of housing conditions as an indirect result of some other life event, for example employment relocation, natural disaster, and the housing improvement is not part of a discrete programme these participants and the studies will not be included. All physical house types which are static (that is not caravans or house boats) will be included, this may include residential establishments providing permanent accommodation and sheltered housing. Housing interventions will be defined as rehousing and any physical change to housing infrastructure, for example heating installation, insulation, double glazing and general refurbishment where aspects of the housing fabric is improved. Physical improvements tailored to meet the needs of the resident will be included, for example medical priority housing. Where these improvements are limited to provision of indoor furniture or equipment, such as vacuuming, mattresses and air purifiers, these will be excluded. Studies which provide no specific information on the nature or extent of the physical housing improvement or focus on non-physical aspects of being rehoused will be excluded. For example, a study may report on the health effects of former residents of supported living quarters being relocated to live independently. It may be mentioned that the physical quality of the new housing is superior to previous accommodation but details of what the actual physical improvements are may be omitted as the intervention of interest to such a study is primarily the move to independent living. Such a study would be excluded. Studies will be included if they have investigated changes in health, illness or wellbeing related outcomes among the residents following the delivery of a discrete housing improvement programme which has been delivered following and as a consequence of a natural disaster or labor migration. It is possible that following and as a consequence of such an event some of the population will live in improved housing. However studies will not be included where the study investigates the health and socio-economic effects of an event such as a natural disaster or economic migration but where no discrete programme of housing improvement has been delivered to the population. Environmental studies of the adverse effects of lead, urea formaldehyde foam, air quality, allergens or radon will not be included. These studies assess the impact of exposure to the potential hazard rather than any impact of housing improvement. In addition, evidence of the harmful effects of radon, lead and asbestos are now accepted (Wilkinson 1999). Primary outcomes Outcome measures will include any measure which can be interpreted as a direct measure of health, or mental and physical illness, general measures of self-reported wellbeing and quality of life measures. Data on health service use will be extracted and reported but will not be included in the final synthesis. Studies which only report health service use outcomes will be reported to ensure provision of a comprehensive list of studies which have assessed heath related outcomes. These studies will not be included in the final synthesis. There will be no minimum follow-up period to assess health effects. Where a study reports on health impacts at multiple time points all impacts will be extracted and reported. The final impact will be used as the study's findings. In the case where synthesis across more than one study is possible, the outcomes from the most similar time point across the studies will be used. Secondary outcomes Additional social and socio-economic outcomes which can be interpreted as determinants of health will be extracted, where reported; for example fuel costs, household income, measures of social contact, social exclusion, education, employment, time off work. An example of the search strategy illustrating the search terms to be used is available in Appendix 2. The strategy and combination of terms used will be amended as required for each database. The search strategy will not be limited with respect to population characteristics such as age, gender, language, or race. The search strategy will include terms relating to public provision of housing aimed at low-income populations. Bibliographies of screened papers and identified reviews will be searched for eligible studies. Efforts to identify relevant grey literature will include contacting experts, searching SIGLE/COPAC, handsearching IDOX (formerly PLANEX), and searching relevant websites both within the UK and beyond. A list of experts from the lead review authors' own contacts and authors of housing studies will be contacted by e-mail to request any information about completed or ongoing studies which might be relevant to the review. The results of the searches will be screened independently by two review authors to identify studies which meet the review's inclusion criteria. The initial screening will be based on study title and abstract. Where there is disagreement or ambiguity about inclusion the full reference will be obtained to allow further scrutiny of the eligibility of the study. The review authors will meet to discuss studies where there is disagreement over inclusion or exclusion of a study. Citations will be stored in EndNote (bibliographic software). Assessment of risk of bias will be conducted by two review authors independently and disagreements resolved by discussion. The reported findings from each study will be extracted by one review author and checked by a second review author with disagreements or inaccuracies to be discussed between the authors. All data will be entered into an Access database and checked by a second review author. The final agreed data extraction will be entered into RevMan by one review author. A list of data extraction fields is available in Appendix 3. The data extraction will include extraction of intervention context and the socio-demographic characteristics of the study sample, such as gender, race, age, and socio-economic status. Quantitative studies We will complete the Cochrane risk of bias tool for each study. It is expected that this tool will not be sensitive to the variations in study quality across the various study designs included in this review, such as non-randomised studies and uncontrolled studies. For this reason, studies will also be assessed for risk of bias using a critical appraisal tool developed by a group of systematic reviewers in Hamilton, Canada (Hamilton Assessment Tool) (Thomas) and that has been recommended by the Cochrane Public Health Group for use in reviews of public health interventions where non-randomised studies are included (Armstrong 2008). We propose amending the Hamilton Assessment Tool to ensure that it is appropriate to studies of housing interventions, for example by including an assessment of key confounders accounted for beyond socio-demographics, such as eligibility for housing improvement and housing condition at baseline. Also, the Hamilton Assessment Tool (HAT) does not differentiate between prospective controlled study designs and other non-randomised study designs; we propose to amend the tool to allow distinctions between controlled and uncontrolled study designs. Our proposed amended HAT to assess risk of bias is presented in Appendix 4. Using this tool, each study will be assessed for the extent of bias introduced to the study with regard to selection of study population, study design, control for confounding, data collection measures and methods, blinding of assessor and participants, and withdrawals by final follow up. Each of these potential areas of bias will be graded as A, B, or C (A indicating minimal potential bias and C indicating considerable potential for bias) according to the criteria outlined in Appendix 4. The quality assessment for each study will be carried out by two independent review authors and entered onto a Microsoft Access© database. Disagreements in any one of the six points of assessment (selection, study design, confounding, data collection, blinding, withdrawals) will be resolved through discussion between the two review authors. Each study will be assigned to a summary category (A, B, or C) indicating the overall potential for bias. The criteria for this summary category are outlined in Appendix 4. Qualitative studies Qualitative studies, including studies reporting qualitative data supplementary to quantitative data, will be included in the review. There is much unresolved debate about appropriateness of assessments of the quality of qualitative studies and their data. Despite this, it is important to present details of the study design, sample, and data collection methods, as well as an indication of the review authors' appraisal of the validity of the reported findings and their interpretation. Data on the study aims and methods, including sampling details and data collection methods, will be extracted and tabulated to provide an overview of the study design and methods. In addition, a critical appraisal tool developed for qualitative studies and previously recommended for use in systematic reviews will be used, such as the tool developed by the Joanna Briggs Institute. Intervention implementation and performance bias Variation in the ways in which an intervention is implemented may introduce bias and explain variance in the reported effects within a study (Type III error) (Dobson 1980). This may be referred to as performance bias. It cannot be assumed that the housing improvements were implemented as originally planned, or that all recipients of the intervention used the intervention in the same way. Variation in intervention implementation may result in variation in exposure to the critical changes that the intervention aims to affect and will result in variation in the potential to benefit within a study. For example, the extent of housing improvement may be tailored according to individual household need and will vary, therefore, by the housing condition at baseline. In addition, delivery of a housing improvement may not result in exposure to improved housing conditions. For example, fear of costly fuel bills may prevent use of a new central heating system, or if an intervention is implemented without assessment of need there may be households where the potential to improve housing conditions is limited if housing conditions are satisfactory at baseline. Included studies will be assessed for within study heterogeneity with respect to intervention implementation and also for heterogeneity in the extent of improvement in housing conditions actually experienced by participants (see Appendix will be used to for all health outcomes from controlled studies which report data. These outcomes will be likely to include and and the will be reported as an and Housing interventions are and implemented at a household to households eligibility criteria or to all households within a However, health outcomes are assessed at an individual In some studies health outcomes are only assessed for one and in health outcomes are assessed for more than one or for all occupants these assessments may be on of other occupants by a The type is likely to vary across the identified studies. We will all reported health and socio-economic outcomes for however occupants have been included in the study. Where a study data for the are likely to be or gender, with specific illness for example or not Other of interest with respect to equity indicators are race or ethnicity, occupation, socio-economic education, religion. For the and data will be reported and Data and on other mentioned in particular those with equity will be extracted, reported and where there are similar data. We will authors of studies to data. We will report withdrawals and levels of for each study and these into the overall indication of study will be used to for controlled studies which report the data. heterogeneity will be assessed using the and a of will be conducted using a a will be within and between the studies will be investigated and reported with respect to study design, study quality, and implementation of the the on and of for a more detailed of heterogeneity between the studies will be and also implementation and performance for details of heterogeneity with respect to implementation and performance bias will be We will investigate the impact of bias by a and if there are studies which report for the Quantitative data Data from the quality studies will be and the final synthesis will the of evidence within each group of studies. It is that there will be levels of heterogeneity within the collection of studies identified. It has previously been recommended that measures to heterogeneity be where possible, to a These measures include of of studies with respect to interventions and and use of a 2008). from studies will be for all prospective controlled studies identified using Where data for similar outcomes following similar housing improvements and interventions as outlined in and of are available these will be Where the same is reported across more than one study a will be the software). These will be in a to a Where a is an will be will be assessed using and a of will be conducted using a a will be considered for Where are not to due to a will be used to the range of Where the outcomes within a category are similar but not the for example measures of health, and they are a of and we will present as and present in a to allow all the to be The data from both and outcomes will be using the of experimental and quasi-experimental studies will be For groups of studies where a synthesis of the data is not appropriate the data will be according to the 2006). The of the synthesis will involve a of housing improvement might lead to health impacts (see the intervention might a synthesis to the the in the data and between similar and the of the synthesis. The data from each study will be tabulated to provide a as well as a summary of the this will the synthesis by illustrating with respect to reported impacts and study characteristics as well as the of the synthesis. To present a clear of what studies have been identified, these studies to quality studies, and why they have not been included in the final a of all studies, of study design, will be included in the final review with an of all studies and reported impact data. This information will provide a of intervention research in this and to point to future research design be improved within this field. Qualitative data The synthesis of data from multiple qualitative studies has been as to the qualitative approach and It has been that between studies with respect to and means that to data will the and of the data that the of specific individual and However, that qualitative data can impacts not or by quantitative studies and also light on important factors and which may explain the variance in health these data may be to other similar populations and It is expected that the qualitative studies will be with respect to context and population, as well as and study For these we propose to conduct a synthesis of the qualitative data in with the on synthesis 2006). The findings from each study will be tabulated to provide a summary of the data. This will a and of with respect to reported and health We will assess heterogeneity for aspects including respect to heterogeneity of interventions, the synthesis will be carried out for groups of studies which include similar interventions, as below. methods, population, and outcomes The of this review will that the identified studies will variance in the used, the interventions being the study and in which the intervention is being and

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