**1. Introduction**

The mission of the United States (U.S.) Centers for Disease Control and Prevention's National Institute for Occupational Safety and Health (CDC/NIOSH) is rooted in its dedication to preserving and enhancing the total health of workers. This mission—to generate knowledge in the field of occupational safety and health and to transfer that knowledge into practice for the betterment of workers—generated the *Total Worker Health*® (TWH) program. As of 2015, the TWH framework is defined as policies, programs, and practices that integrate protection from work-related safety and health hazards with promotion of injury and illness prevention efforts to advance worker well-being [1]. TWH efforts protect the safety and health of workers and advance their well-being by fostering safer and healthier workplaces and by addressing work organization, employment and supervisory practices, and workplace culture. Integration can ensue through collaboration and coordinated programming around organizational leadership and commitment; supportive organizational policies and practices; management and employee engagement strategies; supportive benefits and incentives; accountability and training; and integrated real-time evaluation and surveillance that bring about corrective action where required [2]. Frameworks and models have been published to help describe what integration is like in practice [3–5].

The original emergence of the TWH approach at NIOSH began years prior with the Steps to a Healthier U.S. Workforce Initiative in 2003, which explored the benefits of integrating worker safety and health protection efforts with health promoting ones [6]. As research developed and implementation increased, the focus on the integration of health protection and health promotion expanded to a framework with a greater appreciation of (and demand for) a growing set of worker well-being determinants that impact safety and health. In 2014, as initiatives evolved and more research and information became available, NIOSH launched the Office for TWH Coordination and Research Support (Office for TWH) to coordinate and advance research, programs, policy, and training in collaboration with intramural and extramural partners [7]. A comprehensive history on the evolution of the TWH program prior to 2014 is available elsewhere [6,8].

Some traditional occupational safety and health (OSH) and worksite wellness programs (that is, non-integrated, stand-alone, siloed approaches) have had a favorable impact. However, scientific evidence has increasingly found that for tackling the wide-ranging, complex concerns of workers, integrating OSH protection activities with health-enhancing ones may be more efficacious than concentrating on either of these activities alone [2,8–10]. More specifically, studies have shown that emphasizing a TWH or integrated approach to jointly and comprehensively address work-related hazards and other exposures addresses the synergistic risks that exist, engendering more promising efforts and results [8].

There has been much headway in the field of TWH over the past several years, and the TWH program has continued to develop. Integration efforts have expanded to consider the synergistic opportunities between and among the health of workers at and away from work and a broader look at the interplay of work and non-work factors and influences on the well-being of workers. This article provides an update on the TWH program since the 2013 publication by Schill and Chosewood [6] and describes its evolution from 2014 to 2018—including major program accomplishments and stakeholder and partnership activities—as well as highlights of future directions.

#### **2. Discussion**
