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Publications

Publications by Daniela Santos

2025

A comparative analysis of unsupervised machine-learning methods in PSG-related phenotyping

Authors
Ghorvei, M; Karhu, T; Hietakoste, S; Ferreira Santos, D; Hrubos Strom, H; Islind, AS; Biedebach, L; Nikkonen, S; Leppaenen, T; Rusanen, M;

Publication
JOURNAL OF SLEEP RESEARCH

Abstract
Obstructive sleep apnea is a heterogeneous sleep disorder with varying phenotypes. Several studies have already performed cluster analyses to discover various obstructive sleep apnea phenotypic clusters. However, the selection of the clustering method might affect the outputs. Consequently, it is unclear whether similar obstructive sleep apnea clusters can be reproduced using different clustering methods. In this study, we applied four well-known clustering methods: Agglomerative Hierarchical Clustering; K-means; Fuzzy C-means; and Gaussian Mixture Model to a population of 865 suspected obstructive sleep apnea patients. By creating five clusters with each method, we examined the effect of clustering methods on forming obstructive sleep apnea clusters and the differences in their physiological characteristics. We utilized a visualization technique to indicate the cluster formations, Cohen's kappa statistics to find the similarity and agreement between clustering methods, and performance evaluation to compare the clustering performance. As a result, two out of five clusters were distinctly different with all four methods, while three other clusters exhibited overlapping features across all methods. In terms of agreement, Fuzzy C-means and K-means had the strongest (kappa = 0.87), and Agglomerative hierarchical clustering and Gaussian Mixture Model had the weakest agreement (kappa = 0.51) between each other. The K-means showed the best clustering performance, followed by the Fuzzy C-means in most evaluation criteria. Moreover, Fuzzy C-means showed the greatest potential in handling overlapping clusters compared with other methods. In conclusion, we revealed a direct impact of clustering method selection on the formation and physiological characteristics of obstructive sleep apnea clusters. In addition, we highlighted the capability of soft clustering methods, particularly Fuzzy C-means, in the application of obstructive sleep apnea phenotyping.

2024

CLUSTERING ANALYSIS OF OXIMETRY PARAMETERS IN MILD OBSTRUCTIVE SLEEP APNEA PATIENTS

Authors
Amorim, P; Ferreira-Santos, D; Drummond, M; Rodrigues, PP;

Publication
SLEEP MEDICINE

Abstract

2020

Identifying baseline clinical features of people with COVID-19

Authors
Ferreira-Santos, D; Maranhao, P; Monteiro-Soares, M;

Publication

Abstract
Objectives: To describe baseline clinical characteristics of adult patients with COVID-19. Methods: We conducted a scoping review of the evidence available at LitCovid, until March 23th, 2020, and selected articles that reported the prevalence of socio-demographic characteristics, symptoms and co-morbidities in adults with COVID-19. Results: In total, 1 572 publications were published on LitCovid. We have included 56 articles in our analysis, with 89% conducted in China, and 75% contained inpatients. Three studies were conducted in North America and one in Europe. Participants age ranged from 28 to 70 years, with balanced gender distribution. Proportion of asymptomatic cases were from 2 to 79%. The most common reported symptoms were fever [4-99%], cough [4-92%], dyspnoea/shortness of breath [1-90%], fatigue 4-89%], myalgia [3-65%], and pharyngalgia [2-61%], while regarding co-morbidities we found cardiovascular disease [1-40%], hypertension [0-40%] and cerebrovascular disease [1-40%]. Such heterogeneity impairs the conduction of meta-analysis. Conclusions: The infection by COVID-19 seems to affect people in a very diverse manner and with different characteristics. With the available data it is not possible to clearly identify those at higher risk of being infected with this condition. Furthermore, the evidence from countries other than China is, at the day, too scarce.

2024

Cool Solutions in Hot Times: The Case for Digital Health in Heatwave Action Plans (Preprint)

Authors
Loureiro, MD; Jennings, N; Lawrance, E; Ferreira-Santos, D; Neves, AL;

Publication

Abstract
UNSTRUCTURED

As climate change drives increasingly severe heatwaves, the strain on public health systems continues to grow, particularly for vulnerable populations. Our work argues for the integration of digital health technologies into heatwave action plans, drawing lessons from the COVID-19 pandemic's success in deploying such tools. It explores the potential of digital communication strategies, telemedicine, and data-driven simulations to enhance public awareness, maintain healthcare accessibility, and improve real-time crisis responses. Despite their effectiveness, digital solutions remain underutilized in existing European heat-health action plans. We emphasize the need for a proactive, systems-based approach to optimize heatwave management and ensure equitable healthcare access, particularly for at-risk communities. Integrating digital health innovations can transform heatwave response strategies, making them more flexible, efficient, and capable of saving lives.

2024

The Utility of Annual Reassessment of the International Working Group on the Diabetic Foot Diabetes-Related Foot Ulcer Risk Classification in the Primary Care Setting-A Cohort Study

Authors
Monteiro-Soares, M; Dores, J; Alves-Palma, C; Galrito, S; Ferreira-Santos, D;

Publication
DIABETOLOGY

Abstract
Background: We assessed the pertinence of updating the International Working Group on the Diabetic Foot (IWGDF) risk classification yearly in people with diabetes by quantifying the changes in the risk group and its accuracy in identifying those developing an ulcer (DFU) in a primary care setting. Methods: In our retrospective cohort study, we included all people with diabetes with a foot assessment registry between January 2016 and December 2018 in the Baixo Alentejo Local Health Unit. Foot-related data were collected at baseline after one and two years. DFU and/or death until December 2019 were registered. The proportion of people changing their risk status each year was calculated. Accuracy measures of the IWGDF classification to predict DFU occurrence at one, two, and three years were calculated. Results: A total of 2097 people were followed for three years, during which 0.1% died and 12.4% developed a DFU. After two years, 3.6% of the participants had progressed to a higher-risk group. The IWGDF classification presented specificity values superior to 90% and negative predictive values superior to 99%. Conclusion: Foot risk status can be safely updated every two years instead of yearly, mainly for those at very low risk. The IWGDF classification can accurately identify those not at risk of DFU.

2020

Identifying common baseline clinical features of COVID-19: a scoping review

Authors
Ferreira Santos, D; Maranhao, P; Monteiro Soares, M;

Publication
BMJ OPEN

Abstract
Objectives Our research question was: what are the most frequent baseline clinical characteristics in adult patients with COVID-19? Our major aim was to identify common baseline clinical features that could help recognise adult patients at high risk of having COVID-19. Design We conducted a scoping review of all the evidence available at LitCovid, until 23 March 2020. Setting Studies conducted in any setting and any country were included. Participants Studies had to report the prevalence of sociodemographic characteristics, symptoms and comorbidities specifically in adults with a diagnosis of infection by SARS-CoV-2. Results In total, 1572 publications were published on LitCovid. We have included 56 articles in our analysis, with 89% conducted in China and 75% containing inpatients. Three studies were conducted in North America and one in Europe. Participants' age ranged from 28 to 70 years, with balanced gender distribution. The proportion of asymptomatic cases were from 2% to 79%. The most common reported symptoms were fever (4%-99%), cough (4%-92%), dyspnoea/shortness of breath (1%-90%), fatigue (4%-89%), myalgia (3%-65%) and pharyngalgia (2%-61%), while regarding comorbidities, we found cardiovascular disease (1%-40%), hypertension (0%-40%) and cerebrovascular disease (1%-40%). Such heterogeneity impaired the conduction of meta-analysis. Conclusions The infection by COVID-19 seems to affect people in a very diverse manner and with different characteristics. With the available data, it is not possible to clearly identify those at higher risk of being infected with this condition. Furthermore, the evidence from countries other than China is, at the moment, too scarce.

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