Figure 2.

Maximum survivorship in response to diet restriction (DR) is comparable in CByB6F1/J and UM-HET3 (HET3) mice. The figure shows the effect of DR on the proportion of diet-restricted mice in the longest-lived 40% of females and 40% of males for each stock. Statistical analysis employed a nominal logistic model to compare the proportion of diet-restricted mice in the longer-lived 40% survivorship with the proportion of DR mice in the shorter-lived 60% survivorship. Because the effect of DR was sex dependent (interaction of sex and diet, p = .04, likelihood ratio chi-square test), further analysis was separated by sex. Among both males and females, DR increased maximum life span (p < .0001, likelihood ratio chi-square test) comparably in both HET3 and CByB6F1 mice (no significant interaction of stock with diet for either sex). Mice are the same as in Figure 1, except that we dropped all censored mice but one (the “longest-lived” censored mouse) because they could not be unequivocally assigned to a survivorship group. Group sizes were as follows: CByB6F1 females, 32 mice; HET3 females, 29 mice; CByB6F1 males, 29 mice; and HET3 males, 28 mice. Numbers of mice in the lower 60% survivorship were as follows—CByB6F1 females: 16 AL, 3 DR; HET3 females: 13 AL, 4 DR; CByB6F1 males: 13 AL, 4 DR; and HET3 males: 11 AL, 6 DR. AL = ad lib.