Delirium is one of the most common and most frustrating syndromes we encounter in medicine. It is also one of the most normalized. Up to 30 to 50 percent of hospitalized older adults experience delirium, particularly in intensive care and post-acute settings, yet it is frequently treated as an expected complication rather than a reversible condition with identifiable drivers. We expect it. We document it. We treat around it. And too often, we accept it. But what if some cases of delirium are not just multifactorial noise, but a signal we are missing?
Over the past several months, I witnessed a series of events that fundamentally changed how I approach acute cognitive decline in medically complex patients. A close family member of mine developed recurrent episodes of severe delirium following a myocardial infarction complicated by acute kidney injury requiring dialysis. The presentation was classic: disorientation, visual hallucinations, fluctuating attention, and profound cognitive impairment. Each episode triggered appropriate evaluation. Infection was ruled out. Oxygenation was stable. Medications were reviewed. Metabolic panels were examined. Imaging was unremarkable. The workup was thorough and consistent with standard of care.
And yet, the delirium persisted. At that point, I began to consider a variable that is rarely prioritized in acute care settings: micronutrient depletion.
Micronutrient depletion as a metabolic signal
Specifically, thiamine deficiency. Thiamine is essential for glucose metabolism in the brain. Without it, neurons cannot generate the energy required to function. The result is not subtle. It can present as confusion, inattention, and, in more severe cases, the syndrome we recognize as Wernicke’s encephalopathy. We are trained to associate this condition with chronic alcohol use. But thiamine deficiency is not an alcohol diagnosis. It is a metabolic one. And it is likely underdiagnosed. Autopsy studies have suggested that Wernicke’s encephalopathy may be missed in up to 70 to 80 percent of cases during life, particularly in non-alcoholic patients.
The risk factors were all present: Prolonged poor oral intake, acute illness with increased metabolic demand, and importantly, renal replacement therapy. Dialysis has been shown to reduce circulating levels of water-soluble vitamins, including thiamine, contributing to deficiency states in vulnerable patients. Empiric high-dose intravenous thiamine was initiated. Within 24 hours, the change was striking. Cognition returned to baseline. Attention normalized. Executive function was restored. The delirium resolved.
Then it happened again. Following subsequent aggressive dialysis sessions, the same pattern emerged: acute delirium followed by rapid resolution after thiamine administration. The response was reproducible. In one instance, thiamine was not administered during hospitalization despite ongoing delirium. Symptoms persisted for a week. After discharge, intramuscular thiamine was given, and cognitive function again returned to baseline within a day.
The striking response to micronutrient administration
This was not a subtle effect. It was a reversible condition behaving like an irreversible one. We often describe delirium as multifactorial, and that is true. But “multifactorial” can become a cognitive shortcut, allowing reversible contributors to be overlooked. Thiamine deficiency is not rare in medically complex patients. Studies have shown that a significant proportion of critically ill and malnourished patients have low thiamine levels, even in the absence of alcohol use. And perhaps more importantly, it is treatable.
The risk of empiric thiamine administration is low. The potential benefit is profound. What happens when we miss these reversible contributors is not benign. Delirium is not just a transient inconvenience. It is associated with accelerated cognitive decline, prolonged hospitalization, increased risk of institutionalization, and higher mortality. In some patients, what begins as an acute confusional state does not fully resolve and becomes the new baseline.
The brain, particularly in older adults, does not always recover from prolonged metabolic stress. Ongoing neuronal dysfunction, inflammation, and energy failure can lead to lasting impairment. What may begin as a reversible deficiency state can, over time, contribute to irreversible injury.
Addressing the human cost of misdiagnosis
There is also a human cost that is harder to quantify. Families often witness a rapid and unrecognizable change in someone they know to be cognitively intact. They see confusion, agitation, or withdrawal and are told this is expected, or part of aging, or reflective of an underlying decline. Clinicians, working under time pressure and pattern recognition, may assume a baseline level of cognitive impairment that is not actually present.
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But many of these patients are, in fact, highly functional at baseline. They are independent, engaged, and cognitively sharp. The delirium is not who they are. It is something happening to them. When reversible causes are not identified and treated, we risk mislabeling an acute, treatable condition as chronic decline. And once that label is applied, the trajectory of care can change in ways that are difficult to undo.
Emerging research is also beginning to explore the role of thiamine in chronic neurodegenerative conditions, including ongoing investigations supported by the National Institutes of Health into its potential impact on cognitive decline in Alzheimer’s disease. While distinct from acute delirium, this line of research reinforces a broader point: The brain’s dependence on micronutrient sufficiency is more clinically significant than we often acknowledge. If we are willing to aggressively search for infection, structural abnormalities, and medication effects, we should be equally willing to consider whether the brain has the biochemical resources it needs to function. Because sometimes, what looks like irreversible decline is anything but. It is a reversible, treatable condition hiding in plain sight.
This essay is cited in the KevinMD record on aging and dementia.
Carrie Friedman is a dual board-certified psychiatric and family nurse practitioner and the founder of Brain Garden Psychiatry in California. She integrates evidence-based psychopharmacology with functional and integrative psychiatry, emphasizing root-cause approaches that connect neuro-nutrition and gut–brain science, metabolic psychiatry, immunology, endocrinology, and mind–body lifestyle medicine. Carrie’s clinical focus bridges conventional psychiatry with holistic strategies to support mental health through nutrition, physiology, and sustainable lifestyle interventions. Her professional writing explores topics such as functional medicine, autism, provider well-being, and medical ethics.
