This study will recruit people who were infected with COVID-19 at least 2 months ago and continue to experience symptoms related to infection. Initially thought to be an acute illness like the flu, resulting in death for some or full recovery in most, scientists and clinicians are now appreciating that substantial numbers of COVID-19 illness survivors experience persistent, significant and sometimes disabling symptoms. Variously called Long-COVID, COVID long-haulers, or chronic COVID syndrome, some of the most prominent symptoms are neurologic and neuropsychiatric, including cognitive impairment ('brain fog'), headache, fatigue, muscle aches and weakness, shortness of breath, hair loss and pain, among others. In this research study the investigators want to learn about whether taking Niagen (also known as Nicotinamide riboside, or NR), a daily supplement containing a form of Vitamin B3, can improve recovery of cognitive function, mood, and physical health in individuals who were infected with COVID-19 and continue to experience brain fog and other neurological and physical symptoms. The investigators think that this supplement may help improve thinking skills and other symptoms, and improve quality of life, in individuals who had COVID-19.~Participants will complete the following at baseline and every 5 weeks: 1) a standard cognitive battery and subjective cognitive complaints scales; 2) mood measures; 3) assessments of physical functioning, as well as of other common COVID-19-related symptoms; 4) blood draw; and 5) 2 optional MRIs. Participants will also wear a Fitbit and complete questionnaires to assess sleep and physical activity.
The study will assess whether Niagen, a safe dietary supplement, improves recovery of COVID-19 related symptoms in individuals who were infected at least 2 months prior to study entry (Long-COVID Long-haulers). 60% of participants will receive Niagen and 40% will receive PBO. Outcomes will consist of standardized cognitive, neuropsychiatric, physical, functional and biomarker assessments.