Patients with FM experienced a worsening in their health status after confinement during the COVID-19 pandemic in our cohort. Because we initially excluded all patients who had had clinical manifestations compatible with COVID-19, the worsening of their health status may be attributed directly to the stressors surrounding the confinement.
To our knowledge, this is the first study specifically designed to analyze the impact of COVID-19 pandemic quarantine on the health status in patients with FM. In a recent study  evaluating the impact of confinement on patients with various chronic diseases, the authors found that 48% of them had worsened their perceived health status. Our findings show that the impact of confinement on FM patients is probably similar to that of any other chronic disease.
In patients who reported a worsening of their health status after confinement, the total score of ICAF, as well as the physical factor (which measures variables such as pain, sleep quality or daily life activities), and the emotional factor (which mainly measures anxiety and depression), showed no significant differences with the situation before confinement, suggesting that there had not been a clear worsening of the main clinical manifestations of FM. Only passive coping (which measures the patient's attitude towards their disease along with the coping strategies they are able to develop) was significantly worse both in the previous situation and after confinement. In this sense, 80% of the patients who were worse had already had a predominant passive coping before confinement.
It is noteworthy that passive coping has little influence on the total score of the ICAF questionnaire explaining only 6% of the variance in the construction of the questionnaire, with the physical and emotional factors being the most relevant . This suggests that the perceived worsening among FM patients in our study as a result of COVID-19 pandemic confinement depends primarily on how patients cope with their disease, without a real impairment of the clinical manifestations measured by physical or emotional factors. In the general population, some variables such as female sex, the absence of higher education, the number of people at home or lonely, are associated with a worse situation after confinement . On the other hand, in patients with chronic diseases the variables associated with worsening are also related to aspects of daily life and do not seem to be related to the clinical manifestations of the disease, except for the duration of the disease itself . In other situations of collective stress in society, such as the World Trade Center terrorist attack in 2001, there was also no significant worsening of symptoms in FM patients . In this study, previous depressive pathology was also unable to predict worsening of symptoms, as well as previous FM symptoms such as pain or other psychiatric symptoms .
In addition to the psychological impact of confinement, as we have studied here, there are other possibilities for the COVID-19 pandemic to produce an impairment in the health situation of FM patients. Currently it is not known whether the infection with corononavirus SARS-cov2 may produce long-term chronic clinical manifestations such as fatigue, myalgias, arthralgias or cognitive alterations compatible with chronic fatigue syndrome or FM, as we know to occur in other infectious viral diseases .
If the current COVID-19 pandemic lasts much longer, as it seems to be happening, an increase in new FM cases may occur, especially among the most predisposed patients or those with other chronic inflammatory disease that adds another major stressor for these patients.
The main strength of our study is that we have a measure of quality of life in FM patients prior to the confinement by the COVID-19 pandemic that has allowed us to compare with the situation after the confinement. Several limitations are present in our study. First, the low response rate of 57%, which may underestimate the impact of confinement on FM. Second, we did not collect other relevant variables such as level of education, the number of people at home or lonely, which have been associated with a worse situation after confinement in the general population. Third, our results need to be evaluated in other cohorts of FM patients.