Brewer, D. D., & Roberts, J. M., Jr. Investigating spatial mobility and social predictors of common illnesses. Presentation at the 32nd International Sunbelt Social Networks Conference, Redondo Beach, CA, March 16, 2012. Presentation available at SSRN: http://ssrn.com/abstract=2817141.

Public health advice about preventing common respiratory and gastroenteric illnesses has little empirical basis. To add to the limited epidemiologic research in the general population, we conducted a long-term prospective study of time-varying factors associated with common illnesses in natural circumstances.

An open cohort of volunteers participated in the Health Tracking Network, reporting on their illness symptoms and potentially related factors in daily to weekly web surveys. We analyzed data from 49 adult participants who lived in the northern hemisphere (82% in North America, 18% in Europe) during the winter of 2011-2012 and had multiple weeks of reports. These participants contributed 474 person-weeks of observations (median = 11, range = 2-13).

There were 8 cases of gastroenteritis in the 49 participants, and 17 cases of the common cold in 26 participants who also reported on respiratory symptoms. Travel more than 100 kilometers from home was not longitudinally associated with subsequent illness of either type. Visiting others' homes was modestly longitudinally associated with subsequent common cold and gastroenteric illnesses. Having a symptomatic household member was moderately longitudinally associated with a subsequent common cold illness, even after adjusting for other exposures and some demographic characteristics. However, most cases of the common cold did not involve prior exposure to a symptomatic household member.

The results from our small study allow multiple interpretations and also suffer from several limitations. Future epidemiologic research should be designed to lessen these shortcomings.

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