Is space-time clustering evident in CD?

Cluster (epidemiology) from Wikipedia
"A cluster refers to a grouping of health-related events that are related temporally and in proximity."

Epidemiology from Wikipedia

"Analysis of space time patterns of disease risk" from The Department of Epidemiology and Public Health, Imperial College London

"Crohn's disease in Nottingham: a search for time-space clustering" in Gut (1975)
"Applying the Knox and Pike and Smith tests for clustering of patients in time and space, no significant results were observed. "

"Clustering of Crohn's disease in a Cotswold village" in Q J Med (1986)
"The identification of such a cluster suggests that environmental factors may be important in pathogenesis."

"Crohn's disease--is there a long latent period?" in Postgrad Med J (1986)
"Four cases of Crohn's disease developing in adult females, who had been in close contact during their teens, are described. It is suggested that this could indicate an infective causation for Crohn's disease with a long latency."

"Is There Clustering of Inflammatory Bowel Disease at Birth?" in Am. J. Epidemiol. (1991)
"Results from the entire study penod and after 1944 thus provide evidence for clustering by birth (including seasonality) among Crohn’s disease cases and also, to a lesser extent, among ulcerative colitis cases."

"A Population-based Ecologic Study of Inflammatory Bowel Disease: Searching for Etiologic Clues" in Am. J. Epidemiol. (2006) [full article]
"Incidences of Crohn's disease and ulcerative colitis were observed to be highest among non-Aboriginal persons, persons of high socioeconomic status, persons with the lowest rates of enteric infection, and persons with the highest rates of multiple sclerosis. ...

Thematic maps have shown a pronounced geographic concentration of both Crohn's disease and ulcerative colitis incidence in the outer suburbs of Winnipeg and in southwestern Manitoba. ...

We found a positive association of both Crohn's disease and ulcerative colitis with higher socioeconomic status, paralleling our findings in a previous ecologic study (5). This observation is consistent with the “hygiene hypothesis,” which suggests that persons with higher living standards may be protected from childhood infections because of cleaner environments and smaller households but are more susceptible to chronic intestinal inflammation in adulthood as a result of responding to infectious agents later in life. ...

[T]here may be important differences as to the timing of infection in childhood when infections are contracted. Infections acquired during the immediate perinatal period or early infancy may establish aberrant immune responses to microbes encountered at a later time, while early- to mid-childhood infections may promote tolerance to like organisms. ...

The most novel finding of interest is the significant association between areas with a high incidence of IBD and areas with a high incidence of multiple sclerosis. ... Multiple sclerosis, like IBD, is thought to possibly be a complex T-cell-mediated disorder. ...  This nonrandom clustering supports the notion that susceptibility to clinically distinct autoimmune diseases may be influenced by a common set of genes.  ... Recently, it was proposed that refrigeration and proliferation of psychrotropic bacteria might be responsible for the upswing in Crohn's disease in developed nations during the latter half of the 20th century"

"STUDY APPROVED – Northport Crohn’s/Colitis/IBD – Past & Present Residents info Needed!"

"Dr. Josh Korzenik and Dr. Sharyle Folwer from Massachusetts General Hospital’s, in cooperation of the Crohn’s and Colitis Foundation of America, received the funding and approval to conduct an epidemiological study of Northport residents, both current and past, who have been diagnosed with ulcerative colitis, crohn’s, or any other IBD disease. "