A total of 4957 sworn police officers in North America (United States 97%, Canada 3%) volunteered to participate in either the online or on-site study component. The on-site portion of the study included intense investigations of amunicipal police department serving 1 of the 10 largest US cities and a state police department serving 1 of the 10 most densely populated states. The participating police departments were not from the same state. The on-site cohort was included to achieve a high cooperation rate within those departments and to compare characteristics of responders and nonresponders (in the municipal police department). The online cohort was included to provide a comparison group of police officers from across North America. Both cohorts included monthly follow-up surveys. To recruit for the online cohort, we corresponded with large law enforcement agencies across North America to solicit participation and placed advertisements in police magazines and newsletters and on police-focused Web sites. For the on-site cohorts, we solicited participation from several municipal and state police departments. Ultimately a municipal department and a state department were selected and agreed to participate in the study protocol. Of the 3329 potential attendees from the departments participating in the on-site study, 2004 participated in informational sessions. In addition, 4018 registered for the online study. Of these police officers, 4957 completed the baseline survey, which included a sleep disorders screening: 1264 (63.1%, cooperation rate18) in the on-site cohort and 3693 (91.9%, participation rate18) in the online cohort, which made them eligible for the crosssectional analyses.18 In both cohorts, the 3545 officers who had completed at least 1 of the monthly follow-up surveys were eligible for the prospective analyses: 1264 in the on-site and 2281 in the online cohort. This represents a 63.1% cooperation rate and 56.8% participation rate, respectively; these were deemed the prospective study cohort. The study protocol was approved by the Partners Human Research Committee and was conducted between July 2005 and December 2007. Participants provided written or electronic informed consent and were not informed about study hypotheses. For reporting purposes to the human research committee and to funding agencies, participants were required to self-report race and ethnicity using prespecified categories. Participants selected for polysomnography studies received up to $440, and survey participants were eligible for a prize drawing valued at up to $1000.
Design
In a cross-sectional baseline survey, we assessed demographics, physical
and mental health status, and the risk of sleep disorders. For up to 2
years following the baseline screening, each month we sent all
participants an e-mail with a link to a short online survey assessing
work-related performance, work hours, and safety. Reminder e-mails were
sent to those who did not immediately complete the survey. (The baseline
screening questions and follow-up surveys are available from the
authors.)