Health impact, and economic value, of meeting housing quality standards: a retrospective longitudinal data linkage study

Background Poor-quality housing adversely affects residents’ health but there is a paucity of high-quality evidence to support this. Objective This research investigated the health impact of bringing housing to a national quality standard. Design A natural experiment of improvements to housing quality analysed using repeated measures of health-care utilisation and economic outcomes at an individual person level. Setting Carmarthenshire, UK. Participants A total of 32,009 residents registered for a minimum of 60 days at 8558 social homes that received housing improvements between January 2005 and March 2015. Interventions Multiple internal and external housing improvements, including wall and loft insulation, windows and doors, heating system upgrades, new kitchens and bathrooms, garden path safety improvements and electrical system upgrades (adding power sockets, and extractor fans in kitchens and bathrooms). Main outcome measures Emergency hospital admissions for cardiorespiratory conditions and injuries. Primary health-care utilisation for respiratory and common mental health disorders, emergency department injury attendances and health-care utilisation costs. Data sources Carmarthenshire County Council home address and intervention records were anonymously linked within the Secure Anonymous Information Linkage databank to demographic information from the Welsh Demographic Service data set; hospital admission data from the Patient Episode Dataset for Wales; primary care contacts and prescribed medications from general practice data; emergency department attendances from the Emergency Department Data Set; and deaths from the Office for National Statistics mortality register. Methods The study used a longitudinal panel design to examine changes in standard of eight housing cointervention from intervention records, and linked to individuals registered at intervention homes. Health outcomes were obtained retrospectively for each individual in a dynamic cohort and were captured for up to 123 consecutive months. An additional local authority region could not be utilised as a comparator owing to different reporting pressures resulting in the recording of a different intervention. The exposure group for each cointervention was compared with an internal reference group of people living in homes that did not receive the cointervention during their tenancy. A multilevel modelling approach was used to account for repeated observations for individuals living in intervention homes. Counts of health outcomes were analysed using negative binomial regression models to determine the effect of each cointervention that reached housing quality standards during an individual’s period of tenancy, compared with those living in properties that did not. We adjusted for potential confounding factors and for background trends in the regional general population. A cost–consequences analysis was conducted as part of the health economic evaluation. Results Residents aged ≥ 60 years living in homes in which electrical systems were upgraded were associated with 39% fewer admissions than those living in homes in which they were not [incidence rate ratio (IRR) 0.61, 95% confidence interval (CI) 0.53 to 0.72; p < 0.01]. Reduced admissions were also associated with windows and doors (IRR 0.71, 95% CI 0.63 to 0.81; p < 0.01), wall insulation (IRR 0.75, 95% CI 0.67 to 0.84; p < 0.01) and gardens and estates (IRR 0.73, 95% CI 0.64 to 0.83; p < 0.01) for those living in homes in which these cointervention were upgraded. There were no associations of change in emergency admissions with upgrading heating (IRR 0.91, 95% CI 0.82 to 1.01; p = 0.072), loft insulation (IRR 0.98, 95% CI 0.86 to 1.11; p = 0.695), kitchens (IRR 0.98, 95% CI 0.83 to 1.17; p = 0.843) or bathrooms (IRR 0.93, 95% CI 0.81 to 1.06; p = 0.287). Limitations There was no randomisation, there were incomplete data on the scale of the intervention for individual households and there were no estimates for the impact of the whole programme. Conclusions This complex interdisciplinary study found that hospital admissions could be avoided through improving housing quality standards