About the research
Understanding the role that our homes play on our health is important for researchers and health policymakers, as we spend a large proportion of our time in our home environment, particularly if we live in a cold climate. Whilst seasonal fluctuations in weather are known to affect human health, particularly blood pressure and cholesterol levels, the effect that indoor temperature has on health has been less studied. Dr Ivy Shiue has carried out two pieces of research in this area, investigating the impact of indoor temperature on high blood pressure and other biomarkers.
In the first study Dr Shiue used the Scottish Health Survey 2010, a country-wide, population-based study of people living in Scotland, to compare blood pressure readings taken by nurses with the temperature participants kept their home at. This study found that individuals living in homes with an indoor temperature below 18 °C were at greater risk of high blood pressure and those who lived in homes with a temperature below 16 °C had an even greater risk. Dr Shiue concluded that 9% of hypertension in the Scottish population could be prevented if homes in Scotland were heated at above 18 °C.
Having undertaken this research, Dr Shiue has then expanded her research to include the temperature of homes in England. Her second study, this time using the English Longitudinal Study of Ageing 2012-12, considered adults over the age of 50 years and again compared health and home temperature. In this research the study was broadened to include other signs of poor health and alongside high blood pressure considered poor handgrip, lower vitamin D levels, higher cholesterol levels and worse lung conditions. The study found that one in six older adults in England live in what could be considered a cold home (one that is heated at less than 18 °C) and that these adults had an increased rate of markers for poor health. Those living in colder homes had high blood pressure readings, worse handgrip, lower vitamin D levels, higher cholesterol levels and worse lung conditions. These individuals were also less likely to have their blood pressure checked as well.
Methodology
In the first study, produced in collaboration with Dr Mercedes Shiue of McGill University, Canada, Indoor temperature below 18 °C accounts for 9% population attributable risk for high blood pressure in Scotland, data was extracted from the Scottish Health Survey 2010. This survey covers information on demographics, living and work conditions, lifestyle factors, blood pressure readings and indoor temperature measurements. The study covariates include age, sex, body mass index, education level, annual household income and marital status, which were based on previous work by Dr Shiue on the social factors that impact on hypertension. Analyses of the data involved chi-square test, t-test and logistic regresssion modelling, with adjustments made to control for covariates. Indoor temperature was used as a continuous variable and several different cut-offs were used to make the modelling binary. Effects were estimated by using odds ratios and 95% confidence intervals, with P<0.05 being considered statistically significant.
The second study, Cold homes are associated with poor biomarkers and less blood pressure check-ups: English Longitudinal Study if Ageing, 2012-2013, analysed biomarkers and room temperature recorded during nurse interviews with older adults. The study exposure variable was room temperature measured on the day of the interview, which was measured at the same time blood pressure was checked. As in the previous study, cold homes defined as those with a room temperature under 18 °C. Study outcomes were a series of biomarkers that were measured in the blood and lung. Differences were examined by using t test or chi-square test while associations were examined by using a generalised linear model, with P<0.05 considered to be statistically significant.
Impact
Findings for policy
This research shows a clear link between colder homes and poorer health, particularly for older adults. Encouraging warmer homes and increasing public awareness of the adverse effect of low indoor temperature could have a positive impact in reducing hospital admissions due to cardiac or respiratory conditions and have more a general effect of improving individuals’ health. Dr Shiue summarised the collective need to ensure warm homes:
“For clinical practice, maintaining an indoor temperature at 18 °C or above should be implemented throughout the year to optimize human health and wellbeing… designing homes that could retain sunshine for longer periods of time could be considered as well. These aspects would therefore need policymakers, clinicians, nursing staff, community workers, architects, urban planners and civil engineers to work together in order to protect the public’s health and to maintain wellbeing and quality of life when facing the extended life expectancy in the coming decades.”
Dr Shiue’s research has been included in an evidence review on minimum home temperature thresholds for health in winter carried out by Public Health England. The aim of this review was to provide evidence on the health impact of cold indoor temperature and to provide guidance for minimum home temperature. Public Health England recommended that homes should be heated at 18 °C, or slightly above, particularly for people over the age of 65 or with underlying health problems. This recommendation was included in the Keep Warm Keep Well leaflet produced for the general public by the government and incorporated into the 2015 Cold Weather Plan for England.
To read the reports in full:
Shiue. I., Shiue, M. (2014) ‘Indoor temperature below 18 °C accounts for 9% population attributable risk for high blood pressure in Scotland’, International Journal of Cardiology, 171(1), pp. e1-e2.