Influence of depression on the association between colder indoor temperature and higher blood pressure

Cold exposure accounts for more than 7% of all-cause mortality worldwide, and cold-induced blood pressure (BP) elevation and consequent cardiovascular events are partially responsible. For prevention, it is important to identify risk factors for exaggerated temperature-sensitivity of BP but this is not fully understood. This study investigated whether depressive symptoms affect the relationship between indoor temperature and BP.

We conducted a cross-sectional analysis of 1076 community-based individuals who were at least 60 years of age. Depressive symptoms were assessed using the 15-item Geriatric Depression Scale at a cutoff point of 4/5. We performed ambulatory BP monitoring and indoor temperature measurement on two consecutive days during the cold season in Nara, Japan.

When using daytime SBP as a dependent variable, multilevel linear regression analyses showed that lower daytime indoor temperature was significantly associated with higher daytime SBP in the depressive group (n = 216, β = -0.804, P < 0.001) but not in the nondepressive group (n = 860, β = -0.173, P = 0.120); moreover, a significant interaction between depression and daytime indoor temperature was observed (P = 0.014). These relationships were independent of potential confounders including age, gender, BMI, medications, and physical activity. Similar results were obtained for morning SBP, nocturnal SBP dipping, and morning BP surge.

The results suggest that depressive participants are more likely to have cold-induced BP elevation than nondepressive participants. Further longitudinal studies are warranted to determine whether people with depressive symptoms are at a high risk for cold-related cardiovascular events.