Figure 1

Rectal temperature. Changes in rectal temperature (means ± standard error) in summer D (●; n = 7), summer non-D (○; n = 8), winter D (■; n = 7), and winter non-D (□; n = 8) groups. * P < 0.05 compared with summer D (●) and summer non-D (○), ^aP < 0.05 compared with summer D (●) and winter D (■), and ^bP < 0.05 compared with summer non-D (○) and winter non-D (□). In a post hoc test, rectal temperatures at rest (0 min) were lower in winter than in summer for both groups. Rectal temperatures of haplogroup D subjects when exposed to cold during winter were significantly lower at all time points than exposure during summer ( P < 0.05). In contrast, non-D subjects had significantly lower rectal temperatures 0 to 40 minutes after the start of exposure compared with summer ( P < 0.05), but no seasonal difference was seen after 50 minutes. In summer, haplogroup D subjects had higher rectal temperatures than haplogroup non-D subjects 70, 80, and 90 minutes after the start of cold exposure ( P < 0.05)