Spatial and temporal indoor temperature differences at home and perceived coldness in winter: A cross-sectional analysis of the nationwide Smart Wellness Housing survey in Japan.

Residents themselves are responsible for controlling their living environment, and their perception of coldness is important to protect their health. Although previous studies examined the association between perceived coldness and indoor temperature, they did not consider the spatial-temporal differences in indoor temperatures. This study, conducted in Japan, measured indoor temperatures in 1,553 houses across several rooms (living room, changing room, and bedroom) and heights (at 1 m above the floor and near the floor) over two weeks and obtained the perceived coldness from 2,793 participants during winter. Results showed substantial temperature differences between rooms (horizontal differences): 3.8 °C between living and changing rooms, and 4.1 °C between living rooms and bedrooms. The average vertical and diel (evening-morning) temperature differences in the living room were 3.1 °C and 3.0 °C, respectively. Regional analysis revealed that the Tohoku region experienced larger horizontal and diel indoor temperature differences, primarily due to its practice of intermittent and partial heating in living rooms only, in contrast to Hokkaido's approach of heating the entire house continuously. Despite Hokkaido's comprehensive heating system, it exhibited the largest vertical temperature difference of 5.1 °C in living rooms, highlighting the insufficiency of heating alone and the necessity for enhanced thermal insulation. The multivariate logistic regression analyses showed that average temperatures and vertical temperature differences were associated with perceived coldness, while horizontal and diel differences did not show a significant association, further emphasizing the importance of improved thermal insulation. Moreover, factors like individual attributes (age and gender), and lifestyle choices (meal quantity, exercise habits, alcohol consumption, and clothing amount) were significantly associated with coldness perception. Notably, older adults were less likely to perceive coldness but more vulnerable to the health impacts of low temperatures, underscoring the necessity of not solely relying on human perception for indoor temperature management to protect cold-related health problems.

Role of housing in blood pressure control: a review of evidence from the Smart Wellness Housing survey in Japan.

Current countermeasures for preventing hypertension emphasize only improvements to lifestyle. Recently, improving life environment has attracted attention, in parallel with publication of the WHO Housing and health guidelines. We quantitatively evaluated the relationship between housing thermal environment and blood pressure (BP) in a real-world setting. We conducted a nationwide, prospective intervention study-the Smart Wellness Housing survey-in Japan, as a non-randomized controlled trial. The intervention was the retrofitting of thermal insulation in houses. Participant recruitment was done by construction companies in all 47 prefectures of Japan. Measurements of home BP and indoor temperature at 1.0 m above the floor in the living room, changing room, and bedroom were taken for 2 weeks before and after the intervention each winter (November-March) of FY 2014-2019. As of July 2022, over 2500 households and 5000 participants were registered in the database. We found that (1) about 90% of Japanese lived in cold homes (minimum indoor temperature <18 °C), (2) indoor temperature was non-linearly associated with home BP, (3) morning systolic BP (SBP) was more sensitive than evening SBP to changes in indoor temperature, (4) SBP was influenced by indoor temperature change particularly in older participants and women, (5) unstable indoor temperature was associated with large BP variability, and (6) insulation retrofitting intervention significantly reduced home BP, especially in hypertensive patients. We proposed that the BP reduction effect of the life-environment is comparable to that achievable by lifestyle.

[Environmental risks to housing and living arrangements among older survivors of the Great East Japan Earthquake and their relationships with housing type: The RIAS Study].

Objective　Over the course of their lives, people spend most of their time in the home environment. The Community-based Integrated Care System 2018 by the Ministry of Health, Labour and Welfare in Japan declared the importance of "housing" and "living arrangements" as essential elements to enable older adults to live independently and to protect their privacy and dignity in their communities. The present study aims to clarify the relationship between current housing type and "housing" and "living arrangements" among older survivors of the Great East Japan Earthquake (GEJE).Methods　We used data obtained from 3,856 participants, aged 65 years or older, in the Research project for prospective Investigation of health problems Among Survivors of the GEJE (RIAS). Housing types were categorized as follows: "same housing," "temporary housing," "disaster public housing," "new housing" (in a different area), and "others." Healthy housing scores were calculated using a housing health checklist from the Nationwide Smart Wellness Housing Survey in Japan. "Living arrangements" were assessed based on residential status, social network, and social capital. To determine the risks associated with each "housing" and "living arrangement" category, we used multivariate logistic and linear regression models.Results　The number of participants in each housing type was as follows: 2,531 in "same housing," 146 in "temporary housing," 234 in "disaster public housing," 844 in "new housing," and 101 in "others." Compared with those living in "same housing," those living in "disaster public housing," "new housing," and "others" had a significantly higher healthy housing score, whereas those living in "temporary housing" had a lower score. However, with regards to "living arrangements," the number of residents who were living alone was significantly higher among those in "disaster public housing," and those living in "disaster public housing" as well as "new housing" had low social capital compared with those living in "same housing." The likelihood of having a poor social network was substantially higher for those living in "disaster public housing." Sub-scale analyses indicated that "disaster public housing" was associated with less family support, whereas "new housing" was associated with less support from friends.Conclusion　The present results indicate that older survivors-regardless of whether they live in the existing community-find it challenging to establish new social capital and social networks in a new location without the presence of "someone" they knew before the disaster.

Association between Indoor Temperature in Winter and Serum Cholesterol: A Cross-Sectional Analysis of the Smart Wellness Housing Survey in Japan.

AIM: Issuance of the WHO Housing and health guidelines has paralleled growing interest in the housing environment. Despite accumulating evidence of an association between outdoor temperature and serum cholesterol, indoor temperature has not been well investigated. This study examined the association between indoor temperature and serum cholesterol. METHODS: We collected valid health checkup data of 2004 participants (1333 households), measured the indoor temperature for 2 weeks in winter, and divided participants according to whether they lived in a warm (average bedroom temperature ≥ 18℃), slightly cold (12-18℃) or cold house (＜12˚C). The relationship between bedroom temperature and serum cholesterol was analyzed using multivariate logistic regression models, adjusting for demographics, lifestyle habits and the season in which the health checkup was conducted, with a random effect of climate areas in Japan. RESULTS: The sample sizes for warm, slightly cold, and cold houses were 206, 940, and 858, respectively. Compared to those in warm houses, the odds ratio of total cholesterol exceeding 220 mg/dL was 1.83 (95%CI: 1.23-2.71, p=0.003) for participants in slightly cold houses and 1.87 (95%CI: 1.25-2.80, p=0.002) in cold houses. Similarly, the odds ratio of LDL/non-HDL cholesterol exceeding the standard range was 1.49 (p=0.056)/1.67 (p=0.035) for those in slightly cold houses and 1.64 (p=0.020)/1.77 (p=0.021) in cold houses. HDL cholesterol and triglycerides were not significantly associated with bedroom temperature. CONCLUSION: Besides lifestyle modification, improving indoor thermal environment through strategies such as installing high thermal insulation and appropriate use of heating devices may contribute to better serum cholesterol condition.

Frontotemporal EEG as potential biomarker for early MCI: a case-control study.

BACKGROUND: Previous studies using EEG (electroencephalography) as biomarker for dementia have attempted to research, but results have been inconsistent. Most of the studies have extremely small number of samples (average N = 15) and studies with large number of data do not have control group. We identified EEG features that may be biomarkers for dementia with 120 subjects (dementia 10, MCI 33, against control 77). METHODS: We recorded EEG from 120 patients with dementia as they stayed in relaxed state using a single-channel EEG device while conducting real-time noise reduction and compared them to healthy subjects. Differences in EEG between patients and controls, as well as differences in patients' severity, were examined using the ratio of power spectrum at each frequency. RESULTS: In comparing healthy controls and dementia patients, significant power spectrum differences were observed at 3 Hz, 4 Hz, and 10 Hz and higher frequencies. In patient group, differences in the power spectrum were observed between asymptomatic patients and healthy individuals, and between patients of each respective severity level and healthy individuals. CONCLUSIONS: A study with a larger sample size should be conducted to gauge reproducibility, but the results implied the effectiveness of EEG in clinical practice as a biomarker of MCI (mild cognitive impairment) and/or dementia.

[Descriptive epidemiology of winter indoor and outdoor temperatures and their relationships based on SWH survey].

Objectives　The purpose of this study was to make clear the descriptive epidemiology and the relationship between the room temperature of living room, bedroom, dressing room, and outdoor during winter, based on the climate areas in Japan.Methods　This study targeted 3,781 people, survey for 5 years from 2014, based on the Smart Wellness Housing (SWH) project, which was carried out nationwide with the support of the Ministry of Land, Infrastructure, Transport and Tourism. During winter, we recorded the outdoor temperature and living room, bedroom, and dressing room temperatures at 1 m above the floor and near the floor for two weeks. Covariance structure analyses were used to clarify the relationship between room temperature and outdoor temperature based on six climate areas in Japan. The analyses were performed using SPSS22.0 and AMOS22.0 for Windows.Results　The temperature near the floor inside the house was lower than the room temperature at 1 m above the floor, and both the room and near the floor temperature in the morning tended to be the lowest. The temperature disparity between the dressing room and living room was the largest. Based on climate areas, the room temperature in the Area 2 was the highest, while the room temperature in the Area 4 was the lowest. The outdoor temperature was more closely associated with the room temperature near the floor than the room temperature at 1 m above the floor, especially in the southern Areas, except Area 7.Conclusion　The temperature near the floor inside the house was lower than room temperature at 1 m above the floor. The temperature disparity between dressing room and living room was the largest. The room temperature and near the floor temperature were lowest in the energy-saving Area 4. The outdoor temperature was more closely associated with the room temperature near the floor than the room temperature at 1 m above the floor, especially in the southern Areas, except Area 7.

Prospective cohort study of bedroom heating and risk of common cold in children.

BACKGROUND: In countries with mild winter climates and inadequate heating, the relationship between housing conditions and health outcomes in winter have not been well studied. The purpose of the present study was to evaluate the relationship between heater type and temperature factors in the bedroom and incidence of the common cold among children in Japan. METHODS: In this prospective cohort study, we distributed baseline questionnaires and temperature loggers in December 2019 and administered follow-up questionnaires in March 2020. We recruited children under the age of 15 years. We performed Poisson regression analysis and logistic regression analysis. RESULTS: Of 297 participants, air conditioners were the most prevalent (n = 105, 35%), followed by gas or kerosene heaters (n = 50, 17%), and floor heaters (n = 31, 10%). Air-conditioners were associated with higher incidence of all events related to the common cold, especially having a fever (adjusted incidence rate ratio (aIRR) = 1.84, 95% confidence interval (CI): 1.41-2.40). Gas or kerosene and floor heaters showed a lower incidence rate of some events related to the common cold, such as school or nursery school absence (aIRR = 0.55, 95% CI: 0.37-0.82 and aIRR = 0.39, 95% CI: 0.23-0.67, respectively). Bedroom temperature did not show a positive association, but children who always felt cold showed a higher incidence of some events related to the common cold. CONCLUSIONS: Our findings imply that the heating approach and modal thermal comfort, such as location of heating appliances, humidity, airflow, and radiant heat, may be more important for the onset of common cold in children than bedroom temperature itself.

Perception of feeling cold in the bedroom and sleep quality.

Sleep disorders are drawing the attention of both medical and public health concern worldwide. In Japan, research suggests that one fifth of adults do not receive appropriate sleep and 40% of adults sleep less than 6 hours a day, and sleep rates are decreasing further year by year. Many studies show that cold indoor environments negatively affect sleep comfort and quality. Whereas these studies have focused on the effects of low bedroom temperature, few studies have focused on the effect of perception of coldness. Indoor temperature is typically much lower in Japan than in other countries. Therefore, the current study aimed to identify the effect of perception of bedroom coldness on sleep quality among Japanese adults. After controlling for covariates of age, presence of current disease and pain, smoking and consumption of alcohol (Model 1), participants who sometimes, often or always felt cold in the bedroom exhibited 0.57 (95% CI=0.32-0.83, p=<.0001), 1.08 (95% CI=0.82-1.35, p<.0001) or 2.25 (95% CI=1.83-2.67, p<.0001) higher PSQI scores compared to the group which didn't feel cold in bedroom. Our findings suggest keeping the bedroom thermal environment above a minimum limit as recommended by the World Health Organization or other organization during colder, winter nights when feeling cold during sleep. Additional deficiencies in the housing infrastructure, air quality issues due to the use of a heater, and micro bed environment need to be holistically addressed. Sleep quality can be improved by certain level via providing thermally comfortable sleeping environment.

Electrocardiogram abnormalities in residents in cold homes: a cross-sectional analysis of the nationwide Smart Wellness Housing survey in Japan.

BACKGROUND: Excess winter mortality caused by cardiovascular disease is particularly profound in cold houses. Consistent with this, accumulating evidence indicates that low indoor temperatures at home increase blood pressure. However, it remains unclear whether low indoor temperatures affect other cardiovascular biomarkers. In its latest list of priority medical devices for management of cardiovascular diseases, the World Health Organization (WHO) included electrocardiography systems as capital medical devices. We therefore examined the association between indoor temperature and electrocardiogram findings. METHODS: We collected electrocardiogram data from 1480 participants during health checkups. We also measured the indoor temperature in the living room and bedroom for 2 weeks in winter, and divided participants into those living in warm houses (average exposure temperature ≥ 18 °C), slightly cold houses (12-18 °C), and cold houses (< 12 °C) in accordance with guidelines issued by the WHO and United Kingdom. The association between indoor temperature (warm vs. slightly cold vs. cold houses) and electrocardiogram findings was analyzed using multivariate logistic regression models, with adjustment for confounders such as demographics (e.g., age, sex, body mass index, household income), lifestyle (e.g., eating habit, exercise, smoking, alcohol drinking), and region. RESULTS: The average temperature at home was 14.7 °C, and 238, 924, and 318 participants lived in warm, slightly cold, and cold houses, respectively. Electrocardiogram abnormalities were observed in 17.6%, 25.4%, and 30.2% of participants living in warm, slightly cold, and cold houses, respectively (p = 0.003, chi-squared test). Compared to participants living in warm houses, the odds ratio of having electrocardiogram abnormalities was 1.79 (95% confidence interval: 1.14-2.81, p = 0.011) for those living in slightly cold houses and 2.18 (95% confidence interval: 1.27-3.75, p = 0.005) for those living in cold houses. CONCLUSIONS: In addition to blood pressure, living in cold houses may have adverse effects on electrocardiogram. Conversely, keeping the indoor thermal environment within an appropriate range through a combination of living in highly thermal insulated houses and appropriate use of heating devices may contribute to good cardiovascular health. TRIAL REGISTRATION: The trial was retrospectively registered on 27 Dec 2017 to the University hospital Medical Information Network Clinical Trials Registry (UMIN-CTR, https://www.umin.ac.jp/ctr/ , registration identifier number UMIN000030601 ).

Impact of indoor temperature instability on diurnal and day-by-day variability of home blood pressure in winter: a nationwide Smart Wellness Housing survey in Japan.

Home blood pressure (HBP) variability is an important factor for cardiovascular events. While several studies have examined the effects of individual attributes and lifestyle factors on reducing HBP variability, the effects of living environment remain unknown. We hypothesized that a stable home thermal environment contributes to reducing HBP variability. We conducted an epidemiological survey on HBP and indoor temperature in 3785 participants (2162 households) planning to have their houses retrofitted with insulation. HBP was measured twice in the morning and evening for 2 weeks in winter. Indoor temperature was recorded with each HBP observation. We calculated the morning-evening (ME) difference as an index of diurnal variability and the standard deviation (SD), coefficient of variation (CV), average real variability (ARV) and variability independent of the mean (VIM) as indices of day-by-day variability. The association between BP variability and temperature instability was analyzed using multiple linear regression models. The mean ME difference in indoor/outdoor temperature (a decrease in temperature overnight) was 3.2/1.5 °C, and the mean SD of indoor/outdoor temperature was 1.6/2.5 °C. Linear regression analyses showed that the ME difference in indoor temperature was closely correlated with the ME difference in systolic BP (0.85 mmHg/°C, p < 0.001). The SD of indoor temperature was also associated with the SD of systolic BP (0.61 mmHg/°C, p < 0.001). The CV, ARV, and VIM showed similar trends as the SD of BP. In contrast, outdoor temperature instability was not associated with either diurnal or day-by-day HBP variability. Therefore, residents should keep the indoor temperature stable to reduce BP variability.

Housing quality and behavior affect brain health and anxiety in healthy Japanese adults.

Countless studies in animals have shown how housing environments and behaviors can significantly affect anxiety and brain health, giving valuable insight as to whether this is applicable in the human context. The relationship between housing, behavior, brain health, and mental wellbeing in humans remains poorly understood. We therefore explored the interaction of housing quality, weekend/holiday sedentary behavior, brain structure, and anxiety in healthy Japanese adults. Whole-brain structural magnetic resonance imaging (MRI) methods based on gray matter volume and fractional anisotropy were used as markers for brain health. Correlation tests were conducted, and then adjusted for multiple comparisons using the False Discovery Rate method. Housing quality and weekend/holiday sedentary behavior were associated with fractional anisotropy, but not with gray matter volume. Fractional anisotropy showed significant associations with anxiety. Lastly, both weekend/holiday sedentary behavior and housing quality were indirectly associated with anxiety through fractional anisotropy. These results add to the limited evidence surrounding the relationship among housing, behavior, and the brain. Furthermore, these results show that behavior and housing qualities can have an indirect impact on anxiety through neurobiological markers such as fractional anisotropy.

Effect of housing condition on quality of life.

This study examined the housing effect on quality of life among Japanese people. In the current cross-sectional study, we analyzed the 1-year of data (November 2015-March 2016) with 2533 participants. We used the Short Form-8 questionnaire, an 8-item instrument that measures general aspects of health-related QOL. Comprehensive Assessment System for Built Environment Efficiency housing checklist which was developed by Ministry of Land, Infrastructure, Transport and Tourism was used to assess the housing aspects. This checklist has six health elements including thermal comfort, acoustic environment, lighting environment, hygiene, safety, and security for 8 distinctive rooms/places of home. Multilevel analysis was done to identify the relationship between the perceived level of housing problem and PCS and MCS by clustering by sex. Compared to those who always felt unsafe at home due to interior design problem, participants who never felt unsafe showed an average of 10.51 (95% CI = 7.69-13.34, p < 0.0001) and 5.78 (95% CI = 2.90-8.65, p < 0.0001) higher physical and mental component score (better quality of life), respectively. Those who never had thermal, acoustic, lighting, hygiene, and security problems of housing also exhibited significantly better quality of life compared to participants who felt these problems.

Protein intake in inhabitants with regular exercise is associated with sleep quality: Results of the Shika study.

STUDY OBJECTIVES: Although associations between sleep quality and environmental factors and nutrient intake have been reported, interactions between these factors have not been elucidated in detail. Therefore, this cross-sectional study examined the effects of regular exercise and nutrient intake on sleep quality using the Pittsburgh Sleep Quality Index (PSQI), which is the most frequently used index for sleep evaluation. METHODS: The participants included 378 individuals aged 40 years or older living in Shika Town, Ishikawa Prefecture. Of these individuals, 185 met the inclusion criteria. The participants completed a self-administered questionnaire assessing lifestyle habits and frequency and duration of exercise, the PSQI, and the brief-type self-administered diet history questionnaire (BDHQ) on nutrient intake. RESULTS: A two-way analysis of covariance on regular exercise and PSQI scores indicated that protein intake (17.13% of energy) was significantly higher in the regular exercise and PSQI ≤10 groups than in the non-regular exercise or PSQI ≥11 groups (p = 0.002). In a multiple logistic regression analysis with PSQI scores (≤10 and ≥11), protein intake was a significant independent variable in any of the models adjusted for confounding factors such as age, sex, body mass index, current smoker, and current drinker (OR: 1.357, 95% CI: 1.081, 1.704, p = 0.009) in the regular exercise group but not in the non-regular exercise group.Conclusions We identified a positive relationship between sleep quality and protein intake in the regular exercise group. These findings suggest that regular exercise at least twice a week for 30 minutes or longer combined with high protein intake contributes to good sleep quality.

A Prospective Cohort Study of Bedroom Warming With a Heating System and Its Association With Common Infectious Diseases in Children During Winter in Japan.

BACKGROUND: Customarily, bedrooms in Japan are left unheated. Although several studies have reported that the use of a heating system has positive outcomes on respiratory infection and asthma, the preventive effect of heating systems against infectious diseases in children is not well known. METHODS: We conducted a cohort study using two questionnaire surveys, one before the winter season in November, 2018 and the second after winter in March, 2019. Participants were 155 children who did not use a heating system in the bedroom and 156 children who did. RESULTS: Having a heated bedroom with a heating system was associated with decreased odds for the frequency of cold (≥3 times) (adjust odds ratio [AOR] 0.35; 95% confidence interval [CI], 0.19-0.65), duration of fever (≥3 days) (AOR 0.38; 95% CI, 0.22-0.66), duration of medicine for a cold (≥3 days) (AOR 0.91; 95% CI, 0.87-0.95), hospital visit due to cold (≥3 days) (AOR 0.54; 95% CI, 0.31-0.94), absence from school or nursery (≥3 days) (AOR 0.43; 95% CI, 0.27-0.70), influenza infection (AOR 0.43; 95% CI, 0.26-0.71), and gastroenteritis (AOR 0.39; 95% CI, 0.21-0.72). Influenza vaccination reduced the odds of influenza infection (AOR 0.36; 95% CI, 0.22-0.59) and absence from school or nursery (≥3 days) (AOR 0.62; 95% CI, 0.39-0.99). CONCLUSION: This study implies that the heating of bedrooms may have a preventive effect against infections among children. Broader dissemination of this knowledge in Japan will require cultural change through public health awareness.

Impact of Cold Indoor Temperatures on Overactive Bladder: A Nationwide Epidemiological Study in Japan.

OBJECTIVE: To assess the relationship between overactive bladder (OAB) and indoor temperatures in the living room and bedroom. METHODS: Questionnaire data and indoor temperature measurements were obtained from a baseline survey collected during the winter months from November 2014 to March 2019. We performed multiple logistic regression to assess the relationships between OAB and indoor temperatures in the living room and bedroom. RESULTS: The prevalence of overactive bladder was 16.4% among 4782 participants living in 2453 dwellings. The odds of having OAB were higher for participants whose average living room temperature at bedtime was lower than 12°C than for those whose average bedtime living room temperature was at least 18°C (adjusted odds ratio = 1.44, 95% confidence interval: 1.03-2.00). No association was observed between bedroom temperature and OAB. CONCLUSION: These results suggest that thermal comfort in the living room-but not in the bedroom-may improve OAB symptoms. Additionally, using sufficient bedding may prevent cold bedrooms from having a negative impact in terms of OAB. Future studies should focus on housing interventions and education regarding lifestyle modification in patients with OAB.

Comprehensive Fungal Community Analysis of House Dust Using Next-Generation Sequencing.

Fungal community analyses in homes have been attracting attention because fungi are now generally considered to be allergens. Currently, these analyses are generally conducted using the culture method, although fungal communities in households often contain species that are difficult to culture. In contrast, next-generation sequencing (NGS) represents a comprehensive, labor- and time-saving approach that can facilitate species identification. However, the reliability of the NGS method has not been compared to that of the culture method. In this study, in an attempt to demonstrate the reliability of this application, we used the NGS method to target the internal transcribed spacer 1 (ITS1) in the fungal genome, conducted fungal community analyses for 18 house-dust samples and analyzed fungal community structures. The NGS method positively correlated with the culture method regarding the relative abundance of Aspergillus, Penicillium, Cladosporium and yeasts, which represent the major fungal components found in houses. Furthermore, several genera, such as Malassezia, could be sensitively detected. Our results imply that the reliability of the NGS method is comparable to that of the culture method and indicates that easily available databases may require modifications, including the removal of registrations that have not been sufficiently classified at the genus level.

Disparities of indoor temperature in winter: A cross-sectional analysis of the Nationwide Smart Wellness Housing Survey in Japan.

The WHO Housing and health guidelines recommend a minimum indoor temperature of 18°C to prevent cold-related diseases. In Japan, indoor temperatures appear lower than in Euro-American countries because of low insulation standards and use of partial intermittent heating. This study investigated the actual status of indoor temperatures in Japan and the common characteristics of residents who live in cold homes. We conducted a nationwide real-world survey on indoor temperature for 2 weeks in winter. Cross-sectional analyses involving 2190 houses showed that average living room, changing room, and bedroom temperatures were 16.8°C, 13.0°C, and 12.8°C, respectively. Comparison of average living room temperature between prefectures revealed a maximum difference of 6.7°C (Hokkaido: 19.8°C, Kagawa: 13.1°C). Compared to the high-income group, the odds ratio for living room temperature falling below 18°C was 1.38 (95% CI: 1.04-1.84) and 2.07 (95% CI: 1.28-3.33) for the middle- and low-income groups. The odds ratio was 1.96 (95% CI: 1.19-3.22) for single-person households, compared to households living with housemates. Furthermore, lower room temperature was correlated with local heating device use and a larger amount of clothes. These results will be useful in the development of prevention strategies for residents who live in cold homes.

Intervention study of the effect of insulation retrofitting on home blood pressure in winter: a nationwide Smart Wellness Housing survey.

OBJECTIVE: The WHO's Housing and health guidelines (2018) listed 'low indoor temperatures and insulation' as one of five priority areas, and indicated insulation retrofitting to help mitigate the effect of low indoor temperatures on health. However, there is still not enough evidence for the effect of insulation retrofitting based on an objective index. METHODS: We conducted a nonrandomized controlled trial comparing home blood pressure (HBP) between insulation retrofitting (942 households and 1578 participants) and noninsulation retrofitting groups (67 households and 107 participants). HBP and indoor temperature were measured for 2 weeks before and after the intervention in winter. To examine the influence of insulation retrofitting on HBP, we used multiple linear regression analysis. RESULTS: The analyses showed that indoor temperature in the morning rose by 1.4°C after insulation retrofitting, despite a slight decrease in outdoor temperature by 0.2°C. Insulation retrofitting significantly reduced morning home SBP (HSBP) by 3.1 mmHg [95% confidence interval (95% CI): 1.5-4.6], morning home DBP (HDBP) by 2.1 mmHg (95% CI: 1.1-3.2), evening HSBP by 1.8 mmHg (95% CI: 0.2-3.4) and evening HDBP by 1.5 mmHg (95% CI: 0.4-2.6). In addition, there was a dose-response relationship between indoor temperature and HBP, indicating the effectiveness of a significant improvement in the indoor thermal environment. Furthermore, there was heterogeneity in the effect of insulation retrofitting on morning HSBP in hypertensive patients compared with normotensive occupants (-7.7 versus -2.2 mmHg, P for interaction = 0.043). CONCLUSION: Insulation retrofitting significantly reduced HBP and was more beneficial for reducing the morning HSBP of hypertensive patients.

Cross-Sectional Analysis of the Relationship Between Home Blood Pressure and Indoor Temperature in Winter: A Nationwide Smart Wellness Housing Survey in Japan.

Mortality due to cardiovascular disease rises sharply in winter. Known as excess winter mortality, this phenomenon is partially explained by cold exposure-induced high blood pressure. Home blood pressure, especially in the morning, is closely associated with cardiovascular disease risk. We conducted the first large nationwide survey on home blood pressure and indoor temperature in 3775 participants (2095 households) who intended to conduct insulation retrofitting and were recruited by construction companies. Home blood pressure was measured twice in the morning and evening for 2 weeks. The relationship between home blood pressure and indoor temperature in winter was analyzed using a multilevel model with 3 levels: repeatedly measured day-level variables (eg, indoor ambient temperature and quality of sleep), nested within individual-level (eg, age and sex), and nested within household level. Cross-sectional analyses involving about 2900 participants (1840 households) showed that systolic blood pressure in the morning had significantly higher sensitivity to changes in indoor temperature (8.2 mm Hg increase/10°C decrease) than that in the evening (6.5 mm Hg increase/10°C decrease) in participants aged 57 years (mean age in this survey). We also found a nonlinear relationship between morning systolic blood pressure and indoor temperature, suggesting that the effect of indoor temperature on blood pressure varied depending on room temperature range. Interaction terms between age/women and indoor temperature were significant, indicating that systolic blood pressure in older residents and women was vulnerable to indoor temperature change. We expect that these results will be useful in determining optimum home temperature recommendations for men and women of each age group. Clinical Trial Registration- URL: http://www.umin.ac.jp/ctr/index.htm. Unique identifier: UMIN000030601.

Relationship between Perceived Indoor Temperature and Self-Reported Risk for Frailty among Community-Dwelling Older People.

This study investigated the relationship between perceived indoor temperature in winter and frailty among community-dwelling older people. This cross-sectional study included 342 people 65 years and older in Japan. Participants answered questions about demographics, frailty, housing, and perceived indoor temperature in winter. Participants were grouped based on perceived indoor temperature (Cold or Warm) and economic satisfaction (Unsatisfied or Satisfied). Differences in the frailty index between perceived indoor temperature groups and economic satisfaction groups were tested by using ANCOVA and MANCOVA. An interaction effect showed that people in the Cold Group and unsatisfied with their economic status had significantly higher frailty index scores (F(1, 336) = 5.95, p = 0.015). Furthermore, the frailty index subscale of fall risk was the specific indicator of frailty that accounted for this significant relationship. While previous research has shown the risks related to cold indoor temperature in homes, interestingly among those who reported cold homes, only those who were not satisfied with their economic situation reported being at increased risk for frailty. This highlights the potential importance of preventing fuel poverty to prevent frailty.