Cardiovascular diseases are one of the primary causes of mortality worldwide. Paroxysmal atrial fibrillation is a specific type that is difficult to detect and diagnose in a short time frame. To overcome this, we investigated if long-term wearable data can be used for the detection of heart diseases. The BigIdeasLab_STEP dataset and long-term Fitbit data from the ME-TIME study were used to examine this. Our analysis showed a correlation between the window/stride size and accuracy when performing activity classification with the BigIdeasLAB_STEP dataset. Moreover, variability was found between subjects due to differences in the physical structure of their hearts. Normalization proved to be a crucial step to minimize the subject variability and significantly improved performance. Grouping subjects and performing classification inside a group helped to improve performance and decrease inter-subject variability. Integrating handcrafted features in deep learning networks also improved classification performance. Analysis of the long-term Fitbit data showed that there is a difference between individuals based on their health condition. Classification of individual peaks was possible and worked best when utilizing a time series-specific support vector machine and grouping peaks together. Grouping peaks per week from a person and calculating a percentage of heart disease-predicted peaks also worked relatively well to distinguish between heart disease and reference subjects. Like with the previous dataset, normalization proved to be a crucial step to minimize subject variability. The findings indicate that heart rate time series can be utilized for classification tasks like predicting activity or the detection of heart diseases. However, normalization and grouping techniques need to be chosen carefully to minimize the issue of subject variability.

IoT devices have grown rapidly over the past few years. IoT devices are mostly connected to a central server that stores the data and handles end-to-end communication. Due to the increase of IoT devices, the latency with the server increases. Furthermore, when using a central server the data is at risk of being deleted or tampered with. To mitigate these issues blockchain could be integrated with the IoT devices to create a decentralized framework. This paper discusses how IoT integrated with blockchain can solve the problems with data integrity and fault tolerance in current IoT frameworks. Furthermore, different consensus mechanisms are compared and improvements are given to make the mechanisms suitable for IoT devices. The paper concludes by stating that G-PBFT, BFT-SMaRt and Tangle/Jointgraph are the most suitable consensus mechanisms for IoT devices with regard to computational power, throughput, latency and Byzantine fault tolerance. Moreover, two improvements with regard to reducing the latency and increasing the trust in G-PBFT are given.