A negative correlation was observed between height and longevity (r = −0.603, p < 0.05), and between weight and longevity (r = −0.679, p < 0.05). Weight was the significant predictor of life span (p < 0.001), revealing that breeds smaller by weight generally live longer than heavier breeds.
In most animal taxa, longevity increases with body size across species, as predicted by the oxidative stress theory of aging. In contrast, in within-species comparisons of mammals and especially domestic dogs (e.g. Patronek et al., '97; Michell, '99; Egenvall et al., 2000; Speakman et al., 2003), longevity decreases with body size.