The present invention relates to an apparatus a system (100) a method (200) and a computer program for assessing the risk of an exacerbation and/or hospitalization. A patient s physical activity is measured (e.g. by an accelerometer (110)) during an active period of time (e.g. during awake hours) and during arest period of time (e.g. during sleep hours) to gather first and second activity data. A risk of exacerbation and/or hospitalization is assessed (e.g. by a risk assessment unit (120)) based on an expression involving the respective activity data duringactive and rest periods fulfilling a predetermined relationship with respect to a predetermined activity level. For instance low activity data during active periods and high activity data during rest periods indicates an increased risk of exacerbation and/or hospital readmission for the patient. FIG.7
