Objective: To assess how effectively measures adopted in extreme cold in Yakutsk control winter mortality.
Design: Interviews to assess outdoor clothing and measure indoor temperatures; regressions of these and of delayed cause-specific mortalities on temperature. Setting Yakutsk, east Siberia, Russia.
Subjects: All people aged 50-59 and 65-74 years living within 400 km of Yakutsk during 1989-95 and sample of 1002 men and women who agreed to be interviewed.
Main outcome measures: Daily mortality from all causes and from ischaemic heart, cerebrovascular, and respiratory disease.
Results: Mean temperature for October-March 1989-95 was -26.6 degreesC. At 10.2 degrees C people wore 3.30 (95% confidence interval 3.08 to 3.53) layers of clothing outdoors, increasing to 4.39 (4.13 to 4.66; P<0. 0001) layers at -20 degrees C. Thick coats, often of fur, replaced anoraks as temperature fell to -48.2 degrees C. 82% of people went out each day when temperatures were 10.2 degrees C to -20 degrees C, but below -20 degrees C the proportion fell steadily to 44% (35% to 53%) at -48.2 degrees C (P<0.001), and overall shivering outdoors did not increase. Living room temperature was 17.9 (17.2 to 18.5) degrees C at 10.2 degrees C outdoors, 19.6 (18.8 to 20.4) degrees C at -20 degrees C, and 19.1 (18.6 to 19.6) degrees C at -48.2 degrees C. Mortality from all causes and from ischaemic heart and respiratory disease was unaffected by the fall in temperature. Mortality from respiratory disease (daily deaths per million) rose from 4.7 (4.3 to 5.1) to 5.1 (4.4 to 5.7) (P=0.03), but this was offset by a fall in deaths from injury.
Conclusions: People in Yakutsk wore very warm clothing, and in extremely cold weather stayed indoors in warm housing, preventing the increases in mortality seen in winter in milder regions of the world. Only respiratory mortality rose, perhaps because of breathing cold air.