Fatigue and its Longitudinal Associations with Mood, Stress, Anxiety, and Hair Cortisol During the Lockdowns of the COVID-19 Pandemic: A Cohort Study with Ecological Momentary Assessment

Objectives: Fatigue is a debilitating symptom common to many disorders and diseases (including COVID-19) with chronic fatigue affecting an estimated 10.1% of adults. However, fatigue in the general population remains understudied, especially during periods of crisis or sustained societal stress. We aimed to identify psychological and biological factors of fatigue during the COVID-19 lockdowns in the general population and to examine whether early fatigue predicted later fatigue, stress, anxiety, and mood. Methods: In this ecological momentary assessment (EMA) study, 292 participants reported fatigue, stress, anxiety, and mood five times a day for two seven-day measurement periods (20,343 observations) during the two national lockdowns in Austria and Germany. Hair cortisol was obtained from 85 participants as a marker of long-term HPA activity. Results: Fatigue was associated with younger age ( b =−0.27, P <0.001), higher perceived stress over the past month ( b =0.50, P <0.001), higher loneliness ( b =0.29, P <0.001), and lower income ( P <0.001). Lower hair cortisol levels were related to a steeper diurnal increase in fatigue during the first lockdown ( P =0.014). Finally, higher fatigue during the first lockdown was related to higher fatigue, higher stress, and higher anxiety and worse mood during the second lockdown (all P <0.001). Conclusions: Factors associated with high fatigue during the lockdowns of the COVID-19 pandemic were young age, low socioeconomic status, higher perceived stress over the past month, and higher loneliness. Results further suggest hypocortisolism in fatigued individuals during COVID-19. Early fatigue may signal psychological vulnerability during large-scale stressors.