## 1 Introduction  
It is undeniable that cloud computing has a prominent role in the way markets and businesses operate. From the banking and finance industry [1] to manufacturing [2], among others, its adoption is helping leading companies improve their performance across a broad range of services. Typically, a new term is also introduced--Industry 4.0 [3]--in order to describe the Fourth Industrial Revolution and to frame the impact of cloud computing and other emerging technologies, such as the Internet of Things (IoT).  
This, however, could not leave the health sector unaffected. Over the last few years and the evolution of the healthcare sector along with already established technologies such as cloud and edge computing and the Internet of Things (IoT), a significant turn toward the citizens' health data ownership was identified [4, 5]. For this reason, more and more technology companies have been turning toward that direction [6, 7] in order to allow their users to own and be responsible for their own Personal Health Records (PHR), and even countries [8] have already developed patient-oriented systems that provide new capabilities to the citizens, namely allowing them to combine health data from various sources and healthcare institutions in order to provide them complete pictures of their health. However, while the abovementioned initiatives certainly are steps in the right direction, there is still a significant lack of cloud solutions that are citizen- [9] and not healthcare professional-centered [10; 11].  
Not only that, even the works that put the citizen in the front are yet to be engaged in the health sector in a way that the health data obtained and kept by the citizen can be utilized by healthcare professionals and vice versa. While most of the performed research only tried to either assist solely the healthcare professionals or help citizens and individuals to be engaged with their health data [6; 7], our research focuses on merging these two currently separated areas and providing to citizens a better and more secure way of managing their own health data, while also enabling and promoting communication with the professionals.  
In addition, to the best of our knowledge, a lack of services that will assist and accelerate overall communication is identified. Although there exist numerous data prefetching and replication methodologies proposed in the state of the art, there exist none that are entirely health data-related.  
For this reason, this paper proposes a storage cloud solution allowing the citizens to safely store their health data in an encrypted manner using only their mobile devices. In addition, this research work allows the citizens to share this health data with authorized healthcare professionals (HCPs) via their healthcare system during emergency situations. Not only that, in order to significantly reduce the data transmission delay between the storage cloud and the HCPs' system, we propose a novel prefetch engine scheme integrated within the proposed storage cloud. This prefetch engine scheme interacts with the storage cloud when requests are performed by physicians and uses this sequence of requests in order to predict the upcoming request. Once predicted, the predicted health record is replicated to the deployed prefetch component, while the storage cloud is notified to request the file from it.  
The remainder of this paper is constructed as follows. Section 2 presents in detail the state-of-the-art analysis that was conducted prior to the design of both the proposed prefetching scheme as well as the design of the health storage cloud. Section 3 describes the proposed prefetching scheme, the offered storage cloud solution, and how these services are integrated, while Section 4 presents the experiments that were conducted in order to evaluate the prefetching scheme and the overall storage cloud solution and discusses the results. Finally, Section 5 concludes the paper and proposes the next steps based on the current research.