The claim that nightmares may suggest the onset of chronic diseases like lupus is slightly misleading. People may see it as having frequent nightmares means you have lupus or another chronic disease when, in actuality, frequent nightmares could signal a flare-up or worsening of the disease for people who already have it when coupled with other symptoms. According to an article about the same study (https://www.ksl.com/article/51019316/horrific-nightmares-may-signal-oncoming-flare-of-these-chronic-diseases-study-says), although it is true that nightmares and "daymares," dreamlike hallucinations that appear when awake, maybe little-known signs of the onset of lupus and other systemic autoimmune diseases such as rheumatoid arthritis, these symptoms may also be a signal that an established disease may be about to worsen or "flare" and require medical treatment intensely. According to Melanie Sloan, a researcher in the Department of Public Health and Primary Care at the University of Cambridge in the United Kingdom, "We found that lupus patients who were classified as having organ involvement other than the brain, such as kidneys or lungs, often also reported a variety of neuropsychiatric symptoms in the lead up to their kidney/lung flare," "This suggests that monitoring these symptoms — such as nightmares and changing mood — as well as the usual rashes and protein in the urine (due to inflammation in the kidneys), etc., may help with earlier flare detection in many patients, not just those who go on to develop major brain involvement." While this is true for patients in the study with lupus, "It is indeed "perfectly normal" to have occasional nightmares and even daymares, or hallucinations, which "are also more common than we think." Sleep disorder specialist Dr. Carlos Schenck, a professor and senior staff psychiatrist at the Hennepin County Medical Center at the University of Minnesota in Minneapolis, added, "There is no reason for people with occasional nightmares or daytime dreams to be worried they may have an inflammatory autoimmune disease."
The eClinical Medicine study is posted below
https://www.thelancet.com/journals/eclinm/article/PIIS2589-5370(24)00213-X/fulltext