A Realist Review of Contexts and Mechanisms Enabling the Inclusion of Environmental Sustainability Outcome Measures in the Design of Lean Healthcare Interventions

Healthcare systems face increasing pressure to deliver high-quality care while reducing their contribution to environmental harm. Lean quality improvement methods are widely used to reduce waste; however, there is limited understanding of whether and how explicitly integrating environmental sustainability goals into Lean initiatives can generate environmental sustainability outcomes in healthcare. This study addresses this gap by developing program theory to explain how such integration can influence environmental outcomes under specific contextual conditions. A realist review was conducted in accordance with RAMESES publication standards to test and refine seven Initial Program Theories developed in an earlier phase of the inquiry. Environmental sustainability was conceptualized broadly, including reductions in waste, resource use, emissions, and wider system level impacts. Evidence from healthcare and selected non healthcare settings was synthesized to identify recurring patterns of contexts, mechanisms, and outcomes. Four refined program theories were developed: organization-driven, education-driven, individual-driven, and team-driven approaches. Environmental outcomes were more likely when sustainability goals were intentionally embedded within improvement aims and governance structures. Enabling contexts activated mechanisms such as professional motivation and legitimacy, while efficiency-focused Lean initiatives produced limited environmental benefits. The review provides an explanatory framework to guide the integration of environmental sustainability into Lean healthcare improvement practice.