Figure 1.

Survival of aged mice undergoing weekly phase shifts of the light-cycle (A) Survival curves of aged mice undergoing a weekly 6h advance or delay adjustment of the light cycle, compared with unshifted aged controls. On Day 56 survival was 47% in advancers, 68% in delayers, and 83% in unshifted aged mice (group sizes are n=30 for controls and advancers and n=28 for delayers). The distribution of surviving mice at the end of Week 4 (p<0.05) Week 5 (p<0.025), Week 6 (p<0.01), Week 7 (p<0.01) and Week 8 (p<0.05) of the protocol is significantly different than chance (Chi square). Advancers died faster than controls (pairwise Chi square; p<0.01, Day 54) but were only different from Delayers at the ends of Weeks 6 (p<0.01) and 7 (p<0.025) (B) Death rate per week of the protocol. % mortality of remaining mice is plotted for each week in bold. Trend-lines (3-point moving average) for each dataset are shown with dotted lines of the same color. Advancers began dying sooner (all 3 groups chi-square; Weeks 3-4, p<0.025; Weeks 5-6 p<0.05) and the death rate remained higher than the other groups until the final week of the protocol. The death rate in unshifted animals was flat for the duration of the experiment. (C) Survival curves for mice shifted every 4 days. We found that advancers still died at a faster rate (p<0.05 on Day 32; group sizes: 13 advancers, 12 delayers).