Egenvall A, Bonnett B N, Shoukri M, Olson P, Hedhammar A, Dohoo I
Department of Small Animal Clinical Sciences, Faculty of Veterinary Medicine, Swedish University of Agricultural Sciences, PO Box 7037, SE-750 07, Uppsala, Sweden.
Prev Vet Med. 2000 Jul 3;46(1):1-14. doi: 10.1016/s0167-5877(00)00135-5.
The objective of this study was to use several methods to describe the age patterns for risk of death in selected breeds of dogs insured for life in a Swedish animal-insurance company in 1996. Data on eight breeds were analyzed for age at death (including euthanasia). If dogs left the insurance for reasons other than death, they were regarded as censored. Dogs were only insured up to 10 years of age. Four analytical approaches were used. First, descriptive statistics of age distributions (e.g. breed-specific median ages at death, breed- and age-specific mortality risks) were computed. Second, age-specific estimates of survival were calculated using the formula: survival=(1-risk(age<1 year))(1-risk(age 1<2 year))... (1-risk(age 9<1 0 year)). Third, Cox regression (proportional-hazards model) was used to estimate survival and hazard functions. Finally, hierarchically coded Poisson regression was used to determine age-specific cut-points in the risk of death. The hazards from Cox and the incidence-density rates from the hierarchically coded models were transformed to estimates of risk: risk=1-exp¿-(hazard)¿ or 1-exp¿-(incidence-density rate)¿. The breeds studied were Beagle, Bernese mountain dog, Boxer, Cavalier King Charles spaniel, Drever, German shepherd dog, Mongrel and Poodle, together representing over 50000 dogs each year. The yearly breed-specific mortality risk varied between 1.7% (Poodle) and 6.5% (Bernese mountain dog). In all breeds, the risk of death increased with age but the pattern varied by breed. The probability of survival at 5 years of age varied between 94% (Cavalier King Charles spaniel and Poodle) and 83% (Bernese mountain dog, Drever, German shepherd dog) and the survival at 10 years between 83% (Poodle) and 30% (Bernese mountain dog). The survival estimates from Cox and those derived using the combined-risk formula were similar. The cut-point risk estimates provided a simplified picture of when the risk of death changed significantly compared to previous age categories. As anticipated, breeds differed widely in survival up to 10 years of age and there were marked differences in age patterns of mortality. The implications of these findings should be considered in multivariable analyses, where the confounding effect of age is often controlled for using a single age variable common to several breeds.
本研究的目的是运用多种方法描述1996年在瑞典一家动物保险公司投保终身险的特定犬种的死亡风险年龄模式。分析了八个犬种的死亡年龄（包括安乐死）数据。若犬只因非死亡原因退保，则视为删失数据。犬只仅在10岁之前可投保。使用了四种分析方法。首先，计算年龄分布的描述性统计量（例如特定犬种的死亡中位数年龄、特定犬种和年龄的死亡风险）。其次，使用公式计算特定年龄的生存估计值：生存 =(1 - 风险(年龄 < 1岁))(1 - 风险(年龄1 < 2岁))...(1 - 风险(年龄9 < 10岁))。第三，使用Cox回归（比例风险模型）估计生存和风险函数。最后，使用分层编码的泊松回归确定死亡风险的特定年龄切点。将Cox回归的风险和分层编码模型的发病密度率转换为风险估计值：风险 = 1 - exp[-(风险)]或1 - exp[-(发病密度率)]。所研究的犬种有比格犬、伯恩山犬、拳师犬、卡瓦利埃国王查尔斯猎犬、德雷弗犬、德国牧羊犬、杂种犬和贵宾犬，每年这些犬种的犬只数量总计超过50000只。每年特定犬种的死亡风险在1.7%（贵宾犬）至6.5%（伯恩山犬）之间变化。在所有犬种中，死亡风险均随年龄增加，但模式因犬种而异。5岁时的生存概率在94%（卡瓦利埃国王查尔斯猎犬和贵宾犬）至83%（伯恩山犬、德雷弗犬、德国牧羊犬）之间变化，10岁时的生存概率在83%（贵宾犬）至30%（伯恩山犬）之间变化。Cox回归的生存估计值与使用综合风险公式得出的估计值相似。切点风险估计值提供了与先前年龄类别相比死亡风险何时发生显著变化的简化情况。正如预期的那样，各犬种在10岁之前的生存情况差异很大，死亡年龄模式也存在显著差异。在多变量分析中应考虑这些发现的影响，在多变量分析中，年龄的混杂效应通常通过使用几个犬种共有的单个年龄变量来控制。
