While the lifespan advantage of small body size and mixed breed status has been documented repeatedly, evidence for an effect of genetic diversity across dog breeds is equivocal. We hypothesized that this might be due to a strong right-censoring bias in available breed-specific lifespan estimates where early-dying dogs from birth cohorts that have not died off completely at the time of data collection are sampled disproportionately, especially in breeds with rapidly growing populations. We took advantage of data on owner reported lifespan and cause of death from a large public database to quantify the effect of size and genetic diversity (heterozygosity) on mortality patterns across 118 breeds based on more than 40,000 dogs. After documenting and removing the right-censoring bias from the breed-specific lifespan estimates by including only completed birth cohorts in our analyses, we show that small size and genetic diversity are both linked to a significant increase in mean lifespan across breeds. To better understand the proximate mechanisms underlying these patterns, we then investigated two major mortality causes in dogs — the cumulative pathophysiologies of old age and cancer. Old age lifespan, as well as the percentage of old age mortality, decreased with increasing body size and increased with increasing genetic diversity. The lifespan of dogs dying of cancer followed the same patterns, but while large size significantly increased proportional cancer mortality, we could not detect a significant signal for lowered cancer mortality with increasing diversity. Our findings suggest that outcross programs will be beneficial for breed health and longevity. They also emphasize the need for high-quality mortality data for veterinary epidemiology as well as for developing the dog as a translational model for human geroscience.

虽然体型小和混种状态的寿命优势已被反复记录，但遗传多样性对犬种影响的证据是模棱两可的。我们假设这可能是由于在可用的特定品种寿命估计中存在强烈的右删失偏差，其中在数据收集时尚未完全死亡的出生队列中早死的狗被不成比例地抽样，特别是在快速死亡的品种中不断增长的人口。我们利用大型公共数据库中有关所有者报告的寿命和死亡原因的数据，量化了体型和遗传多样性（杂合性）对基于 40,000 多只狗的 118 个品种的死亡率模式的影响。通过在我们的分析中仅包括完整的出生队列，记录并消除特定品种寿命估计的右审查偏差后，我们表明小尺寸和遗传多样性都与品种平均寿命的显着增加有关。为了更好地理解这些模式背后的近似机制，我们随后调查了狗的两个主要死亡原因——老年和癌症的累积病理生理学。老年寿命以及老年死亡率的百分比随着体型的增加而减少，并随着遗传多样性的增加而增加。死于癌症的狗的寿命遵循相同的模式，但虽然大尺寸显着增加了癌症死亡率的比例，但我们无法检测到随着多样性增加而降低癌症死亡率的重要信号。我们的研究结果表明异型杂交计划将有益于品种健康和长寿。他们还强调兽医流行病学需要高质量的死亡率数据，以及将狗开发为人类老年科学的转化模型。