Figure 2 reveals that late-neutered females at 7.4 percent were diagnosed with HSA over 4 times more frequently than intact females with 1.6 percent and early-neutered females with 1.8 percent, both significant differences (RR = 6.10, 95% CI = 1.18, 31.37 and RR = 7.48, 95% CI = 1.79, 31.30
What part of "significant differences" do you not understand?
And, for hemangiosarcoma and mast cell tumor, there wasnt much difference at all between animals neutered early and intact animals. In addition, the overall percentage of animals with those conditions were quite low, less than 5 to 10 per cent.
For female Golden Retreivers only, and which showed very little difference between spayed early and left intact! We're talking 4 or 5 dogs here, in a group of 70, which is quite a small group. There could very well have been a genetic predisposition for those conditions in those particular dogs. The results may very well not be reproducible in a larger population.
It remains to be seen how these results would translate to other breeds. Different breeds have very different rates of cancer, of different types. For some breeds, hemangiosarcoma, lymphosarcoma, and osteosarcoma are not major causes of mortality. For other breeds, they are. For example, in my breed, Irish Wolfhounds, osteosarcoma is very prevalent, it is one of the top three causes of death. Therefore, anything that may affect its occurrence, such as gonadal hormones, is very important to understand, and is one thing we can control. In other breeds, osteosarcoma is very rare, so owners need not worry so much. Hemangiosarcoma and lymphosarcoma are also not rare in IWs so we have to worry about that too.
Goldens though are also at a relatively high risk for some types of cancer, and it is interesting that Hart et al raise the question about whether Golden service dogs should be routinely neutered.
Given the small sample sizes in the GR study, I still question whether the results are truly statistically significant. Or clincially significant. And yes, those results were also statistically insignificant between dogs neutered early and dogs left entire in that analysis.
And, the Rottweiler study did not show a benefit for spaying later than one year.
Last edited by grayarabpony; Apr. 20, 2013 at 12:14 AM.
I found this regarding the use of ratio ratios in statistical analysis, the one used in the Golden Retreiver study: the rate ratio is most suited to study events in a constant domain while the denominator -i.e. the population at risk- is very large.
Overall, the Golden Retriever paper showed a rather modest to zero benefit to keeping a dog intact, for a few conditions. I hope you have changed your mind regarding the Rottweiler study, lol.
It's actually a pretty large study, 700 plus dog's.
The study revealed that, for all five diseases analyzed, the disease rates were significantly higher in both males and females that were neutered either early or late compared with intact (non-neutered) dogs.
Specifically, early neutering was associated with an increase in the occurrence of hip dysplasia, cranial cruciate ligament tear and lymphosarcoma in males and of cranial cruciate ligament tear in females. Late neutering was associated with the subsequent occurrence of mast cell tumors and hemangiosarcoma in females.
In most areas, the findings of this study were consistent with earlier studies, suggesting similar increases in disease risks. The new study, however, was the first to specifically report an increased risk of late neutering for mast cell tumors and hemangiosarcoma.
Furthermore, the new study showed a surprising 100 percent increase, or doubling, of the incidence of hip dysplasia among early-neutered males. Earlier studies had reported a 17 percent increase among all neutered dogs compared to all non-neutered dogs, indicating the importance of the new study in making gender and age-of-neutering comparisons.
The GR study paints an incomplete picture in any case. Why not look at dogs over 8 years of age? Too few left? Why not look at other conditions? The paper states too few cases to look at any other conditions.
You can believe whatever you want, including your incorrect thoughts on the Rottie study.
All due respect, but I tend to believe the results of this study as discussed by the UC Davis researchers, and at least they should be seriously considered. I do have a PhD and education in statistics and assume you do as well.
You are right though, more studies are needed with different breeds and and even broader look at health effects of gonadal hormones. The present studies, while valuable, have only begun to explore the role of gonadal hormones on the health of dogs of various breeds and ages, as I am sure the researchers would be quick to say.