Mild cognitive impairments found years after non-fatal drowning (Research Summary)

What do we already know?

Drowning is a public health problem

In non-fatal drowning cases, limited/lack of oxygen to the brain (hypoxia/anoxia) can lead to brain dysfunction
Non-fatal drowning can be classified as mild, moderate, or severe based on respiratory (i.e., breathing) impairment

In severe drowning cases, cardiac arrest may occur and further limit the supply of blood and oxygen to the brain

Compared with severe drowning patients, moderate drowning patients have been rarely studied

• Neuropsychological assessment is a method to assess cognitive functioning
• After stabilization of their physical condition, most drowning patients are released from hospital without further medical care
• There is little research on cognitive impairments following moderate drowning

What did they want to know?

The overall goal of the study was to understand the effects of hypoxia on thinking (cognition) in moderate drowning patients

The researchers aimed to identify neuropsychological (cognitive) tests that help differentiate between moderate drowning patients and healthy people

What did they do?

15 moderate drowning patients were recruited from a large coastal region of Brazil, as well as 18 healthy participants

• Moderate drowning was classified according to the Drowning Classification
• Drowning patients were assessed 1-5 years after the drowning accident
• The average age of drowning patients was 23.7 years old

All participants completed a neuropsychological assessment that assessed different types of thinking (cognition)

• Memory and learning: Rey Auditory Verbal Learning Test, Brief Visuospatial Memory Test, Digit Span, Rey Complex Figure Test
• Visual spatial ability: Rey Complex Figure Test
• Executive function and attention: Concentrated Attention, Stroop Color Interference Test, Trail Making Test
• Overall intellectual functioning: Vocabulary, Matrix Reasoning

Other measures:

• Clinical questionnaire about drowning
• Mini International Neuropsychiatric Interview (to identify any psychiatric disorders) – 3 of the drowning patients screened positive for PTSD
• MRI (to rule out any brain abnormalities)

What did they find?

Healthy participants and drowning patients showed similar performance for most cognitive abilities

• Vocabulary, non-verbal reasoning, executive function, attention, visuospatial ability, and long-term memory

Certain cognitive abilities of the drowning patients were mildly impaired.

Verbal and visual working memory were impaired.

• Working memory is a type of memory allows a person to temporarily hold a small amount of information that a person actively uses as they perform cognitive tasks.
• E.g., Recalling a set of instructions while you complete a task, holding a number in mind while doing a math problem, remembering where an object was just seen

Verbal fluency was impaired.

• Verbal fluency is your ability to move from thoughts to words quickly (i.e., the ease with which a person can produce words).

Learning was impaired.

• When learning new information, the drowning patients struggled to remember information the first time a piece of information was presented to them, relative to the cognitively healthy participants. However, memory improved significantly after the information was presented a second time.

There was no visible damage found on the structural brain scans.

What does this mean?

Like severe drowning patients, memory was impaired in moderate drowning patients.

• Memory seems to be one of the cognitive functions affected early by a lack of oxygen.

Unlike cases of severe drowning, only verbal fluency, but not more general executive functions (e.g., organization, planning, attention), is affected in moderate drowning patients.

Even years after moderate drowning, mild cognitive impairments may be present.

• Neuropsychological assessment should be available for moderate drowning patients to prevent future problems and provide early access to treatment.

Source:

Nucci, M. P., Lukasova, K., Vieira, G., Sato, J. R., & Amaro Junior, E. (2018). Cognitive performance in transient global hypoxic brain injury due to moderate drowning. Journal of Clinical and Experimental Neuropsychology, 40(5), 462-472.

https://doi.org/10.1080/13803395.2017.1371674

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