SEASONAL-CHANGES IN AMBULATORY BLOOD-PRESSURE IN EMPLOYEES UNDER DIFFERENT INDOOR TEMPERATURES

Objective-The effect of indoor temperature control on summer and winte r ambulatory blood pressure levels at work was studied. Method-Ambulat ory systolic blood pressure (SBP) and diastolic blood pressure (DBP) w ere monitored once in summer and once in winter in 101 healthy normote nsive subjects aged 28-63 years, engaged in similar physical work, fro m two plants with and three without air conditioning. Subjects were in terviewed about health related habits, and measurements of environment al and occupational conditions were obtained. Results-After controllin g for possible confounders, mean SEP and DBP during work were signific antly higher in winter than in summer (Delta SBP = 3.4 mm Hg, P = 0.03 5; Delta DBP = 3.3 mm Hg, P < 0.003). The seasonal change in SBP and D BP showed an independent association with the presence or absence of a ir conditioning of the industrial plants (SBP: beta = 0.194, P < 0.000 1; DBP: beta = 0.054, P = 0.038). The percentage of subjects with incr eases of more than 10 mm Hg from summer to winter was higher in plants without than with air conditioning. Conclusions-(1) In normotensive s ubjects ambulatory working BP varies by season, with higher values in winter. If validated for hypertensive subjects, it may be necessary to tailor drug treatment to these variations. (2) The findings make it c lear that drawing valid conclusions from comparisons of BPs between gr oups requires controlling for several factors, particularly season of the year. (3) Climatic conditions in the industrial plant influence th e magnitude of seasonal variations in BP. Work in plants without air c onditioning places a considerable added load on the employee's cardiov ascular system.