Fig. 4

Hourly heart rate (HR) and 12-h HR of the dark and light periods of the day in a, b 3-month-old; c, d 5-month-old; e, f 14-month-old, g, h 18-month-old male (blue symbols/bars) and female (red symbols/bars) mice. i The change in HR from the dark to light period of the day in male (blue bars) and female (red bars) mice at 3, 5, 14, and 18 months of age. Shading indicates the 12-h dark/light cycle (lights off at 18:00). Hourly data were analyzed using repeated measured ANOVA with the factors sex, time, and their interaction. Twelve hours data were analyzed using a two-way ANOVA with the factors sex, time, and their interaction followed by Bonferroni’s post hoc tests. The dark/light change in HR data were analyzed using a two-way ANOVA with the factors sex, age, and their interaction followed by a Tukey’s post hoc tests. ^# P < 0.05, ^## P < 0.01, ^### P < 0.001, ^#### P < 0.0001 as compared to respective dark period. **P < 0.01, ***P < 0.001, ****P < 0.0001 as compared to respective period in male mice