Differential longevity in mouse stocks selected for early life growth trajectory

Small body size is associated with superior longevity in several intraspeci es comparisons, including dogs bred for specific forms of work, mice and ra ts fed diets low in calories, rats fed diets low in methionine, and mutant mice whose levels of growth hormone and thyroid hormone are atypically low. To further investigate the interactions among body size, genetic endowment , and longevity, we measured the life span of female mice selectively bred from Institute for Cancer Research stock for differences in rate of body we ight gain. These mice were selected for differential rates of growth either early (0-10 days) or later (26-56 days) in the first 2 months of life. The data show a good correlation between the average weight of the stock and i ts mean longevity, with low body size associated, as predicted, with longer life span. Weight at 3, 6, and 12 months, and weight at peak body weight, are all significant predictors of longevity (among stocks) in univariate re gressions; weight at 6 months has the strongest association in stepwise mul tiple regression. There Is no significant correlation between the life span for the stock and the proportion of deaths attributable to neoplasia in th is group of mice. The data provide support for the hypothesis that genetic factors that influence early life growth trajectories can have a strong inf luence on life span. These size-selected mice provide useful tools for anal ysis of the genetic factors that influence life history parameters, includi ng maturation and aging rates.