What investigations should be sent in a patient with suspected sundowning-like phenomenon?

Investigations for Suspected Sundowning-Like Phenomenon

In a patient with suspected sundowning, send baseline blood work (electrolytes, renal function, thyroid function, calcium, HbA1c), perform a comprehensive neurological examination, and systematically screen for underlying medical conditions using the SCREeN framework (Sleep, Cardiovascular, Renal, Endocrine, Neurological disorders) that may be driving the behavioral disturbance. 1

Initial Laboratory Investigations

Core baseline tests should include:

• Electrolytes and renal function to identify metabolic derangements or chronic kidney disease 1
• Thyroid function tests to detect hypo- or hyperthyroidism 1
• Serum calcium to rule out hypercalcemia (which may indicate parathyroid disorders or malignancy) 1
• HbA1c to screen for diabetes mellitus 1
• Urine dipstick and albumin:creatinine ratio to assess for renal disease 1

These investigations target the most common reversible medical causes that can manifest as evening behavioral disturbances, particularly in elderly or cognitively impaired patients.

Neurological Assessment

Perform a detailed neurological examination looking for:

• Lower limb weakness, abnormal gait, or tremor that may indicate Parkinson's disease or other neurodegenerative conditions 1
• Speech disturbances suggesting neurological pathology 1
• Orthostatic blood pressure measurements (taken within 1 minute and at 3 minutes of standing) - a drop of 20 mmHg systolic or 10 mmHg diastolic indicates orthostatic hypotension and autonomic failure 1
• Cognitive impairment or memory loss as "suspicious" symptoms requiring neurology referral 1

Sundowning typically occurs in the context of dementia and represents worsening confusion and agitation in late afternoon/evening 1, 2, 3. The neurological examination helps identify the underlying neurodegenerative process.

Sleep Disorder Screening

Systematically assess for sleep disorders that can mimic or exacerbate sundowning:

• Ask screening questions for obstructive sleep apnea (OSA): "Do you snore and wake up choking?" "Does your partner say you stop breathing?" 1
• Screen for restless legs syndrome (RLS): "Does it vary over the day and worsen in evening?" "Is it relieved by movement?" 1
• Check ferritin levels if RLS suspected - supplementation indicated if below 75 ng/ml 1
• Consider overnight oximetry if OSA is suspected, with referral to sleep clinic 1

Sleep disorders are highly prevalent in patients with dementia and can significantly worsen evening behavioral symptoms 1, 3.

Cardiovascular Evaluation

Screen for cardiac causes of nocturnal symptoms:

• Blood pressure measurement (if not already documented) 1
• Assess for peripheral edema suggesting heart failure or fluid retention 1
• If heart failure suspected: obtain ECG and brain natriuretic peptide; proceed to echocardiogram if positive 1

Cardiovascular disease, particularly congestive heart failure, can contribute to nocturnal restlessness and confusion through impaired cerebral perfusion 1.

Medication Review

Critically evaluate all medications for:

• Drugs causing xerostomia (dry mouth) that increase fluid intake and nocturnal awakenings: anxiolytics, antidepressants (especially tricyclics), antimuscarinics, antihistamines, decongestants, antiparkinsonians, antipsychotics 1
• Diuretics, calcium channel blockers, lithium, NSAIDs that may worsen nocturnal symptoms 1
• Timing of medication doses - particularly diuretics, diabetes medications, and antiparkinsonian drugs relative to bedtime 1

Polypharmacy is a major contributor to sundowning-like phenomena and represents a readily modifiable factor 1.

Additional Investigations Based on Clinical Suspicion

If specific conditions are suspected:

• Morning urine osmolarity after overnight fluid restriction if polyuria >2.5 L/24h despite fluid restriction (concentrations >600 mosm/L rule out diabetes insipidus) 1
• Parathyroid hormone if hypercalcemia detected 1
• Renal ultrasound if chronic kidney disease newly diagnosed 1

Critical Clinical Pitfalls

Common mistakes to avoid:

• Do not assume sundowning is purely behavioral - it often reflects underlying medical derangements that are treatable 1, 2
• Do not overlook delirium - sundowning in dementia can be difficult to distinguish from superimposed delirium, which requires urgent investigation for precipitants (infection, metabolic disturbance, medication toxicity) 1
• Do not forget that symptoms typically worsen in evening - this temporal pattern is characteristic and helps differentiate from other behavioral disturbances 1, 2, 3
• Recognize that multiple factors often coexist - nocturia, sleep disorders, pain, and cognitive impairment frequently overlap in causing evening behavioral disturbances 1

The investigation strategy should be systematic and comprehensive, as sundowning-like phenomena are typically multifactorial with treatable underlying medical causes 1, 2.