Research blog: Welsh care home study finds proportion of residents with dementia a significant risk factor for COVID-19 infection.

A new study using SAIL Databank suggests that environmental and social COVID-19 mitigation measures in care home settings may be more effective in reducing infection than focusing on individual risk factors.

People in the community with dementia have been more likely to be hospitalised with COVID-19, but there is a lack of evidence on  how dementia affects the risks of residents of care homes and how otherindividual and care home-level factors might affect those risks.

This examination of multiple factors shows that care homes with higher proportions of dementia residents across the whole care home setting, placed residents at a higher risk of COVID-19 infection. On an individual level however, only severely frail residents were at higher risk: there was no evidence that a dementia diagnosis put a resident at higher risk of infection compared with the general Welsh care home population.

The study was led by Public Health Wales’ Chris Emmerson and supported by teams at SAIL Databank and Population Data Science at Swansea University Medical School. The team used anonymised, individual-level, population-scale health and demographic records linked to COVID-19 testing data within SAIL Databank. A cohort of care home residents in Wales was created from the period of the pandemic’s ‘second wave’ from September to December 2020 – prior to the vaccination programme rollout.

The researchers studied individual factors such as age, sex, dementia and frailty, and care home setting factors such as the composition of the nursing provision, residential capacity, communal spaces and health board locality.

Lead researcher Chris Emmerson tells us more about the research and the implications of this latest work,

Why did you want to look at COVID, care homes and dementia together?

Care home residents have been particulary vulnerable to COVID-19 infection, so its really important to find good quality evidence for how we can best reduce the risks to them. The early evidence during the pandemic was mostly about how people with specific conditions associated with aging were more at risk. But we knew from early experiences of the pandemic that care homes had particular challenges to deal with, especially when it came to supporting people with dementia. So we wanted to get a clearer understanding of what the risks were in relation to environments, not just medical conditions.

What surprised you about the research findings?

The biggest surprise was that our findings suggest the proportion of residents with dementia in any given care home is much more important than whether an individual has dementia themselves. We’d expected higher risks in homes with more residents with dementia; the kinds of changes to routines and environments that the pandemic forced on care homes created an obvious risk for those with dementia. But the importance of that relationship and the fact that whether or not an individual had dementia didn’t seem to change their risks once that environment was taken into account was unexpected. The significance of dementia in care home covid risk?

A lot of focus on care homes and COVID has been on how individuals are supported: how staff work with each resident to minimise the risk of infection. That’s still important: our study suggests, for instance that those who are frail are more at risk, so we need to think about how to meet their needs. But this study suggests we need to think about how to manage the environment and the resident population as a whole: how are communal areas laid out, how can staff be supported to help those with dementia understand why changes are necessary during outbreaks?  We know these factors matter, but our study suggests they are crucial to planning and implementing infection prevention and control measures.

Why SAIL Databank is a useful tool for studies like this?

The SAIL databank allowed us to link each individual to their care home. This meant that we could use a multilevel design, which accounts for the fact that each indivdual’s risk of infection was related to the other residents. Obviously if you live in a home where lots of other residents have contracted COVID, your risks of infection are higher, quite apart from any other factors that might make you vulnerable. So SAIL allowed us to use a design that accounted for that issue.

But even more importantly, SAIL allowed us to link up a huge range of relevant clinical and care home level factors, so we could test a wide range of risk factors. We looked at age, frailty, dementia, size of the care home, how much communal space was available, the area the home was in: each of these variables had a theory behind it, so we were able to test the evidence for a large number of hypotheses at once. We were very lucky to be able to take advantage of many years of work from other researchers to link these data together; it is a huge privilege to be able to use a dataset like that.

Could the effect of dementia in care homes benefit from further analysis?

There are a number of questions this study raises that would benefit from further research. If we could look at staff across care homes, and see if there were differences between their rates of infection in care homes with with different proportions of residents with dementia we would have even stronger evidence for the importance of that factor, given that staff are not frail or diagnosed with dementia themselves. It would also be very useful to consider patterns of infection amongst residents to see whether initial cases were more or less likely to have a diagnosis of dementia and whether initial cases with dementia were associated with more rapid or widespread infection within the setting. Answers to these questions would help us build a more complete picture of what happens in care homes affected by COVID.

Read the full paper here: