Warmer Homes Could Reduce Cardiovascular Risk in Japan, Study Suggests

Winter brings increased health risks, particularly for cardiovascular conditions such as hypertension. A recent study from the Institute of Science Tokyo found that well-insulated homes, which help maintain warmer indoor temperatures, may significantly reduce the risk of cardiovascular diseases (CVDs) in Japan’s aging population. Published in BMJ Public Health, the research highlights that improved thermal insulation could not only boost health outcomes but also be a cost-effective strategy.

Evaluating Insulation Levels and Health Outcomes

The research team, led by Assistant Professor Wataru Umishio, compared homes with varying insulation grades, noting that over 90% of Japanese homes fall below the World Health Organization's recommended indoor temperature of 18°C (64°F). This is particularly concerning for Japan’s elderly population, who are more susceptible to cold-induced health risks. Using nationwide survey data, the researchers analyzed the relationship between indoor temperature, blood pressure, and CVD risk, creating five home scenarios with differing insulation levels and temperatures.

In scenarios where insulation was upgraded at the age of 40, lifetime costs increased slightly—by 0.26 million to 0.84 million JPY—but insulation costs were largely offset by savings on healthcare, with nearly 74% of costs recovered in Scenario 1–1 and about 58% in Scenario 1–2, primarily due to reduced CVD-related medical expenses. Furthermore, healthy life expectancy rose by up to 0.48 quality-adjusted life years (QALYs), showing significant health gains within Japan’s cost-effectiveness threshold of 5 million JPY per QALY.

Implications for Policy and Future Health Strategies

This study underscores the potential of insulation as a public health intervention, with findings indicating that early insulation upgrades are more cost-effective than retrofitting older homes. Retrofitting, though beneficial, was less financially favorable, as Scenario 2–2 was cost-effective only for those willing to pay 6.5 million JPY or more—exceeding Japan’s typical cost-effectiveness threshold. These results suggest that affordable partial retrofitting or other cost-efficient solutions should be considered for older residences. The study’s findings could inform policies that encourage better housing insulation, aligning with global health and sustainability goals.