Talk:Autism (incidence)
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[edit] Prevalence and Incidence
Prevalence is different from incidence. When I first drafted this I thought it was important enough to define at the top of the page, but that has been nibbled away. I think this predisposes to the continued confusion.
The prevalence of autism and spectral disorders may well be interesting, but it is the argument over the incidence of autism etc that is much more interesting and far more critical in disucssion of causes. If a cause is removed the prevalence will not be reduced rapidly or greatly, however the incidence will be.
Some of the confusion and conflation into "frequency" may be deliberate, some is acidental.
If an examination of the prevalence is desired then it is best to write one. Any remaining prevalence information in this article really should have been stripped out by now, but generating an article by removing everything that shouldn't be in it is is quite a large job. 13:16, 7 December 2007 (UTC)
The US section at present is purely prevalence - not incidence, not change in incidence with time - I think this was a momentary abberation since there has been a lot of good editing going on. Can we remove or revert that please?
One of the few bits of actual information on research-verified incidence in the US - Olmstedt COunty figures - with references that worked when I looked at them has gone away with no discussion. Was that a mistake, or did someone think there was a significant problem with them? Midgley (talk) 13:44, 7 December 2007 (UTC)
- As far as I can tell, all the data presented in this article is about prevalence, not incidence. Which makes sense, since almost all statistics-gathering uses prevalence. Much of the data is incorrectly presented as being about incidence; I haven't gotten around to fixing that. The title of this article is greatly misleading: it should be Autism prevalence rather than Autism (incidence). That will also require some cleanup, though. Eubulides (talk) 21:57, 7 December 2007 (UTC)
- I removed the Olmsted County reference in October because I thought it didn't add much to the U.S. section. Newschaffer et al. 2007's fine review of autism epidemiology (PMID 17367287) doesn't cite that study, which suggests they didn't think all that much of it either. However you are correct that it is about autism incidence (unlike most studies) and since the title of this article ia about incidence it's more relevant than some other studies, so just now I put it back in with a better summary and citation. Eubulides (talk) 22:28, 7 December 2007 (UTC)
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- Thanks. I disagree on two things:-
- 1. There is no preponderance of data on prevalence in the article, and the dicussion is of incidence, not of prevalence. Historically, the source of the article content was an article called variously "Autism Epidemic" or "autism frequency" which was incompletely clear about what it was discussing. I'm unsure what the proportions of statistics gathering on prevalence and on incidence are, even in my own area, but there is a specific reason for looking at incidence rather than prevalence (actually there are several, but this one is relevant) which is if the incidence is actually changing, or if something depends on whether the incidence is changing. The duration of the condition also affects this - prevalence of pneumonia is not very interested, since we don't tend to have beds for it rather than any other acute medical condition, but the incidence is very interesting, rising at this time of year in the N. hemisphere. The incidence of pneumonia or other respiratory conditions in travellers landed recently from aircraft is very interesting, the prevalence of respiratory illness in passengers currently on aircraft may well have something to do with it... but the two figures are not interchangeable. With conditions requiring long complex care the prevalence does affect how much one puts aside for providing it, but the changes in incidence affect how that is projected to change in subsequent years, and is reflected in the age-specific prevalence.
- Most specifically, if something that causes autism stops happening, then there will be almost no change in prevalence. However the cohort reaching the point or age of exposure to that environmental variable will show a sharp decrease in incidence. The incidence may not be measurable until a year or five after that event, but again, we are interested in incidence as a clue to cause, not prevalence.
- Thanks. I disagree on two things:-
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- 2. Autism (Prevalence) is a perfectly reasonable topic to write about, but it should not be this article, and it should not be redirected to this article. The two could be subsumed into an article called Autism (Epidemiology) but that should cover several other aspects and would be a large and probably difficult and unruly topic. Autism (Incidence and Prevalence) would be a reasonable article, I suggest it would best be approached by coalescing two Good Articles one on incidence and one on prevalence and start with a clear description of the difference between the two. Meanwhile I remain surprised that so much argument is present in WP about the rate of change of incidence with so little actual information on the incidence in particualr places at particular times. SOme of it arises from people who are so sure that there is an epidemic that such mundane matters as counting how many cases occur in the cohort born in each successive year is superfluous to their discussions. Midgley (talk) 19:52, 9 December 2007 (UTC)
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[edit] Incidence in sub-groups
The first and last sentences in this are clearly in the right place, the rest I suspect should be removed for the moment, unless there are actual incidence figures or discussions that can usefully be quoted. Midgley (talk) 20:05, 9 December 2007 (UTC)
[edit] Probably prevalence
"
Reports of autism grew dramatically in the U.S. in the 1990s and early 2000s. For example, in 1996, 21,669 children and students aged 6–11 years diagnosed with autism were served under Part B of the Individuals with Disabilities Education Act (IDEA) in the U.S. and outlying areas; by 2001 this number had risen to 64,094, and by 2005 to 110,529.[1]"
[edit] Wrong definition
- The incidence rate of a condition is the rate at which new cases occurred per person-year, for example, "2 new cases per 1000 person-years".
Er, no... Not here. Midgley (talk) 16:32, 10 December 2007 (UTC) I'd try for a definition along the lines of how many of the babies born in a particular place in a particular short time period eventually are shown to be autistic/spectral. The prevalence that is worth directly contrasting with that is the number of people of a particular sort currently living in a particular area. The "particular sort" thing I agree is without a good reference (there was a bad one at one time I think) but I think is a useful thing to put back in with a reference to the assertion that engineers or programmers who mate produce children with a higher risk, and incidence of autism, and I'd say at present the statement that this has not been shown. If we don't then someone will wander by and add it as though true... Midgley (talk) 17:18, 10 December 2007 (UTC)
- The quoted definition is the standard one used in epidemiology. See the cited textbook reference, which says incidence is defined by "relating the numbers of new cases to the person years at risk, calculated by adding together the periods during which each individual member of the population is at risk during the measurement period". A definition related to how many babies eventually have autism is equivalent to the standard definition if we assume that all cases of autism begin at birth, but such an assumption is controversial, as some theories hypothesize that cases of autism are caused by postnatal environmental factors, and a careful article should not make such an assumption without stating it. After all, this article started out as Autism epidemic and was based on environmental theories that are widely popular; we cannot simply ignore them merely because they lack scientific support. Infant mortality also messes up the proposed nonstandard definition. Eubulides (talk) 18:11, 10 December 2007 (UTC)
[edit] This article is actually about prevalence
I agree with much of what you say about incidence and prevalance and so forth, but I'm afraid that with autism things are a bit different than with influenza. Almost all the cited data in this article is about prevalence, not incidence. The article's discussion may be about incidence, but when you follow the references and see what actually is being measured, it's prevalance. And there are some good reasons for this. To quote Autism#Epidemiology, "Autism's incidence, despite its advantages for assessing risk, is less useful in autism epidemiology, as the disorder starts long before it is diagnosed, and the gap between initiation and diagnosis is influenced by many factors unrelated to risk. Attention is focused mostly on whether prevalence is increasing with time." This quote is backed by Newschaffer et al. 2007 (PMID 17367287), the most-recent high-quality review of autism epidemiology that I know of. Eubulides (talk) 20:12, 9 December 2007 (UTC)
- I'm surprised and a little perplexed. I've looked at the references. The word incidence occurs in the titles of several of them. The title of the article is "incidence". I wrote the first go of it by deliberately setting out to remove everything that did not relate to incidence. The last change made was to remove a chunk that doesn't clearly enough relate to incidence rather than prevalence, frequency or "service" in the USA and reinstate a piece specifically on the incidence in Olmstedt county. I'd be fascinated to read the article that I thnk we both agree is not without merit, on autism prevalence, with that being a good name for it. Attention may well be focussed upon prevalence, but I suggest applying a little ray of it to incidence. Midgley (talk) 16:28, 10 December 2007 (UTC)
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- The word incidence does appear in some titles, notably Honda et al. 2005 (PMID 15877763) and Barbaresi et al. 2005 (PMID 15630056), but if you read the sources you'll see that they are talking about cumulative incidence, not incidence rate. In a disorder where the cure rate is essentially zero, there is little practical difference between cumulative incidence and prevalence. For example, Honda et al. 2005 reported cumulative incidence up to age 7; under the reasonable assumption that death and cure rates were negligible, this is equivalent to the point prevalence at age 7. Eubulides (talk) 18:35, 10 December 2007 (UTC)
- This may help to explain why it would be a mistake to have separate articles on autism incidence and prevalence. There should be just one article, which talks about the frequency of autism, and which discusses both incidence and prevalence and clarifies the relation between the two. The vast majority of our audience doesn't care about the fine distinctions between cumulative incidence and point prevalence; what they care about is the risk that their child will be autistic, and whether that risk is increasing or decreasing with time. This audience will be far better served by one article rather than having two dueling articles on essentially the same subject. Eubulides (talk) 18:35, 10 December 2007 (UTC)
