HSP Prevalence

OK, so, in my internet trawl so far I have found several references to the prevalence of HSP in the general population. Some of these prevalence's have been referenced to studies and papers which provide further details. I've managed to find downloads for four different papers which give prevalence for HSP, and these papers all contain summaries to previous prevalence papers. This post combines all these papers together and tries to estimate the prevalence of HSP. I have found some further papers which have not been referenced in any of these four studies, but I'm going to leave those for inclusion in a further post.

So, the four papers I found in full are:
Erichsen et al, Norway, 2009: http://brain.oxfordjournals.org/content/132/6/1577.full.pdf
Monagle et al, Ireland, 2002: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1737699/pdf/v072p00043.pdf
Coutinho et al, Portugal, 1999: http://archneur.ama-assn.org/cgi/content/full/56/8/943
Polp et al, Spain 1991: http://brain.oxfordjournals.org/content/114/2/855.abstract?ijkey=c0472af598cf8de455d3b4f7839277c2f74d87be&keytype2=tf_ipsecsha (this sometimes asked for payment, but other times didn't)

From this, I get an overall list of the following studies into the prevalence of HSP:

Location	1st Author	Year	Cases	Population	Prevalence per 100,000
Guam	Chen	1968	7	37975	18.4
Denmark (Zealand)	Werderlin	1975	23	1179000	2
W. Norway	Skre	1980	31	725000	12.1
Italy (Reggio Emilia)	Lucci	1982	4	412324	1
Libya	Sridharan	1985	11	519000	2.1
Italy (Torino)	Brignolio	1986	31	2327996	1.3
Japan	Hirayama	1989	109	123000000	0.17
Spain (Cantabria)	Polo	1991	49	510000	9.6
Italy (Molise)	Filla	1992	9	335211	2.7
Italy (Valle d'Aosta)	Leone	1995	5	115270	4.3
Portugal	Silva	1997	5	250061	2
Portugal	Coutinho	1999	106	3786000	2.8
Ireland	Monagle	2002	69	5436000	1.27
Norway	Erichsen	2009	194	2633893	7.4

This shows some interesting things to me. Generally these studies all relate to separate geographic areas, apart from there being two Norway and two Portugal, so, I will exclude the earlier and smaller studies from each of these countries to avoid double counting.

The main outliers in the data sets are the studies from Japan and Guam, with the Japan study having by far the largest overall population. On the whole the other studies give broadly the same results, and (apart from Libya) relate to European populations. This gives opportunities for combining data sets:

Analysis	Cases	Population	Prevalence
All studies excluding Skre 1980 and Silva 1997	617	140292669	0.44
All studies excluding Skre 1980 and Silva 1997 and Japan	508	17292669	2.94
All European studies excluding Skre 1980 and Silva 1997	495	16985755	2.91

Some while ago I read Guns Germs and Steel (http://www.amazon.co.uk/Guns-Germs-Steel-history-everybody/dp/0099302780 - a very interesting read) and this leads me to think that conditions would have different prevalence's in different parts of the world. So, I'll concentrate my analysis on the area where the main proportion of studies have been done - Europe. I would suggest that the overall prevalence of HSP in the European population is about 3 per 100,000 population, but noting that several of the papers indicated they thought their studies presented an underestimate.

Perhaps with further analysis I'll be able to draw out some further thoughts...

I was able to find an abstract for all of the papers listed except the Lucci paper of 1982, which appears to be strangely elusive. I would welcome contact from anyone who has a full copy of these papers (or links to other locations) to add to my collection! For completeness, links to abstracts for the other papers follow:

Guam, Chen, 1968: http://archneur.ama-assn.org/cgi/content/summary/19/6/573
Denmark, Werderlin, 1975: http://onlinelibrary.wiley.com/doi/10.1111/ane.1986.73.issue-S106/issuetoc
Norway, Skre, 1980: http://onlinelibrary.wiley.com/doi/10.1111/j.1399-0004.1974.tb00647.x/abstract
Libya, Sridharen, 1985: http://brain.oxfordjournals.org/content/108/4/831.abstract
Italy, Brignolio, 1986: http://www.springerlink.com/content/39x4u4351261153v/
Japan, Hirayama, 1989: http://www.ncbi.nlm.nih.gov/pubmed/8059595
Italy, Filla, 1992: http://www.ncbi.nlm.nih.gov/pubmed/1512613
Italy, Leone, 1995: http://www.ncbi.nlm.nih.gov/pubmed/7793232
Portugal, Silva, 1997: http://www.jclinepi.com/article/S0895-4356(97)00202-3/abstract

The missing reference:
Italy, Lucci, 1982: Lucci B, Motti L, Guidetti D, Zucco R. Indagine epidemiologica descritiva delle eredoatassie nella provincia di Reggio-Emilia. In: Atti del III Convegno Nazionale di Neuroepidemiologia. 1982;p. 169–174