Mark Huisman

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BACKGROUND Variation in the incidence rate in epidemiological studies on amyotrophic lateral sclerosis (ALS) may be due to a small population size and under ascertainment of patients. The previously reported incidence decline in the elderly and a decrease in the male:female ratio in postmenopausal age groups have yet to be confirmed. METHODS ALS(More)
OBJECTIVES This study was performed in order to gather insight into the well-being of Dutch medical residents. METHODS In 2005, all Dutch residents registered through the Medical Registration Committee (n = 5245) were sent a self-report questionnaire to assess socio-demographic and work-related characteristics, burnout and engagement. RESULTS Of the(More)
OBJECTIVE To investigate the association between cigarette smoking, level of education, occupation, and the occurrence of sporadic amyotrophic lateral sclerosis (ALS). METHODS A total of 364 patients and 392 controls completed a questionnaire covering smoking habits, level of education, and occupational history. Main occupations were coded according to(More)
The collection of longitudinal data on complete social networks often faces the problem of actor nonresponse. The resulting incomplete data pose a challenge to statistical analysis, as there typically is no natural way to treat the missing cases. This paper examines the problems caused by actors missing as nominators, but still occurring as nominees, in(More)
In this paper we both describe and analyze the meeting process and the evolution of a friendship network among sociology freshmen in the Netherlands. We develop a theory that explains how changes in the network structure depend on one or more of four main effects: proximity, visible similarity, invisible similarity, and network opportunity. We formulate(More)
Analysis of social network data is often hampered by non-response and missing data. Recent studies show the negative effects of missing actors and ties on the structural properties of social networks. This means that the results of social network analyses can be severely biased if missing ties were ignored and only complete cases were analyzed. To overcome(More)
Sporadic amyotrophic lateral sclerosis (ALS) is believed to be a complex disease in which multiple exogenous and genetic factors interact to cause motor neuron degeneration. Elucidating the association between medical conditions prior to the first symptoms of ALS could lend support to the theory that specific subpopulations are at risk of developing ALS and(More)
Environmental exposure to chemicals and metals may contribute to the risk of sporadic amyotrophic lateral sclerosis (ALS). Two systematic reviews of the literature on these topics performed according to the well-established MOOSE guidelines are presented. Literature cited in MEDLINE, EMBASE, CINAHL, and Cochrane databases (up to March 2007) as well as(More)
BACKGROUND It has been hypothesised that physical activity is a risk factor for developing amyotrophic lateral sclerosis (ALS), fuelled by observations that professional soccer players and Gulf War veterans are at increased risk. In a population based study, we determined the relation between physical activity and risk of sporadic ALS, using an objective(More)