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Issues of consent and data collection in vulnerable populations. (Research Corner).

Some researchers assert that the best therapeutic and preventive care is a combination of expert clinical judgment derived from experience and evidence from a variety of basic and clinical research studies (Sackett, Rosenberg, Gray, Haynes, & Richardson, 1996) delivered in partnership between the healthcare provider and the patient (Rosser, 1999). Because treating illnesses and participating in research studies may carry some risk, informed, voluntary consent is obtained before proceeding with either.

The necessity of obtaining consent before treating a person is a concept dating from ancient times. Plato declared that free men (as opposed to slaves) had the right to consent to (or decline) treatment (Dalla-Vorgia, Lascaratos, Skiadas, & Garanis-Papadatos, 2001). The issue exemplified in Plato's writing was the principle of autonomy of decision making about self. This principle applies to treatment decisions and to decisions about participation in research projects equally. Dalla-Vorgia et al. pointed out that in modern times there is no formal slave class; therefore, all people are considered free and must be allowed to give consent before undertaking medical treatment or participating in research. The National Commission for the Protection of Human Subjects of Biomedical and Behavioral Research (NCPHSBBR, 1979), author of the Belmont Report, noted that treating people as autonomous is an indicator of respect for them.

Informed, autonomous decision making is complex and includes several elements: (a) the process must be free from coercion; (b) the participant must be able to understand the information about treatment options and limitations or research involvement, including the risks and benefits; (c) the participant must believe the information provided is valid; (d) the participant must be able to remember the information; and (e) the participant must be able to weigh the risks and benefits and, in the case of treatment options, understand the effect of choosing no treatment (Mukherjee & Shah, 2001; NCPHSBBR, 1979). The last four tasks are predicated on possession of sufficient background knowledge to put the information in context, ability to attend to the content, ability to use oral and written language, and possession of sufficient executive control function (i.e., the cognitive processes that allow individuals to organize and prioritize complex activities to achieve a specific goal) to complete the task (Royall, Cabello, & Polk, 1998).

A wide variety of sociological or pathological conditions may effectively hold people hostage, rendering them unable to make an informed, autonomous decision by affecting their ability to make truly voluntary decisions, to attend to the environment, or to process language or by affecting executive control functions. Further, effects of illness may compromise the validity of data (Hakamies-Blomqvist et al., 2001). Thus, the very people who are most in need of treatment or research to guide their treatment may be the most vulnerable in terms of decision making. The primary purpose of this article is to help clinicians identify individuals who may be vulnerable when it comes to being informed about treatment options or participation in research studies. Cognitive disability does not necessarily imply that a person's ability to understand a project or treatment option, provide valid data, or give consent is absent. Therefore, the secondary purpose of this article is to provide strategies to assist clinicians in presenting information to those who may have cognitive disability in the most assimilable form possible.

Major Vulnerable Populations

At a societal level, people in the United States lack clear understanding about how much decisional incapacity puts people at risk and therefore have difficulty in tightly defining vulnerable populations (National Bioethics Advisory Council [NBAC], 1998). People commonly thought of as needing protection are those who have been diagnosed with certain dementing illnesses or whose level of consciousness is so depressed as to preclude their interacting well enough to signal that they understand the information and agree to the research or treatment protocol. NBAC has recently identified those with dementing illnesses, delirium, schizophrenia, depression, and other conditions such as mental retardation, bipolar disorder, and substance abuse as being at risk for impaired ability to give informed consent. Earlier, the authors of the Belmont Report identified fetuses, pregnant women, children, and prisoners as being vulnerable (NCPHSBBR, 1979). Agreeing to a treatment proposed by a physician is typically seen as requiring less decisional capacity than declining the treatment (Dickens, 1997). Several assessment strategies can be used. Formal examination with standardized tests or some special capacity assessment instrument can be needed but is time-consuming. Clinical interviews also can be used as screening, or some combination of both can be used (Binder & Guze, 1998). Mukherjee and Shah (2001) made the point that capacity to give consent is specific to each instance of consent giving, with more decisional capacity needed for events that are potentially more harmful.

Sociological Processes That Put People at Risk

The major risk related to autonomy regarding choices of treatment options or participating in research projects is coercion. Flaskerud and Winslow (1998) defined vulnerable social groups as those "who have an increased relative risk or susceptibility to adverse health outcomes" (p. 69). People may be legally free but politically marginalized because of social circumstances and are therefore at risk for coercion in health-related matters.

People with low educational attainment or who lack literacy and numeracy skills may be vulnerable. People with impaired literacy skills may have difficulty with the language, even if documents are read to them. Those with impaired numeracy skills may lack a clear understanding of the odds of treatment success or failure.

Some cultural groups may view members of healthcare teams, some of whom come from an upper-middle-class background, as very powerful. The economically disadvantaged also may be at risk for coercion (Flaskerud & Winslow, 1998). Members of minority groups are often politically marginalized because of language skills, educational attainment, or the social biases of others and thus may also be at risk for coercion. Prisoners are the only members of sociologically marginalized groups in the Untied States to enjoy special protection by institutional review boards (IRBs). All these groups need special care in recruitment for research studies or during explanation of therapeutic strategies.

Physical Processes That May Alter Cognitive Ability

People with pathophysiological conditions that may alter cognition require extra care in the consent process and in the data collection process. These conditions include, but are not limited to,

* pain (Farmer, Cady, Bleiberg, & Reeves, 2000; Heyer et al., 2000; Luoto, Taimela, Hurri, & Alaranta, 1999; Sjogren, Olsen, Thomsen, & Dalberg, 2000)

* psychiatric disorders or psychological stress (Carpenter et al., 2000; NBAC, 1998; Niveau & Kelly-Puskas, 2001)

* metabolic derangements, including electrolyte imbalances, hypo- or hyperglycemia; renal disease

* a variety of neurological disorders; hypoxia; cardiovascular disorders

* hematologic disorders (Burn & Bates, 1998; Grodstein, Wilson, Chen, & Manson, 2001; Hjalmarsen, Waterloo, Dahl, Jorde, & Viitanen, 1999; Noble, Jones, & Davis, 1993; Park, 2001; Petiet, Townes, Brooks, & Kramer, 1988; Vos, Folgering, & van Herwaarden, 1995; Zelinski, Crimmins, Reynolds, & Seeman, 1998)

* sleep deprivation (Dawson & Reid, 1997; Drummond et al., 2000)

* those taking a variety of drugs, including immunosuppressants or antiepileptic drugs (Aldenkamp, 2001; Gray, Lai, & Larson, 1999).

Differences among groups of participants in many of these studies were small, and in some studies the scores of the more impaired groups still would be regarded as being in the normal range. Therefore, cognitive changes may be quite subtle. However, because statistically significant differences were found, even with relatively small samples, they serve as guidance about members of groups that may need extra care in the consent process, the data collection process, or both.

Elderly people are particularly at risk for several of these conditions, including respiratory disorders, diabetes, and the slower metabolism of medications. An interaction effect may exist between age and various chronic diseases that have an effect on cognition. Biedler et al. (1999) found that about 25% of their large sample of people older than 60 years who had major noncardiac surgery were cognitively impaired soon after surgery when compared with controls. Nearly 10% of the sample had impairment at 3 months after surgery. The risk for them may have been anesthesia. Gray et al. (1999) noted that many commonly used drugs may cause cognitive dysfunction in older people because of altered pharmacokinetics. Drugs that have been associated with cognitive dysfunction in the elderly include high-dose aspirin, antidepressants, anticholinergics, and other drugs used to treat Parkinson's disease; antihistamines; metoclopramide; and, perhaps, nifedipine.

Sleep Deprivation

As much as 50% of the general population of the United States is sleep deprived (National Sleep Foundation, 2001). Sleep deprivation, defined as either reduced hours of sleep or fragmentation of sleep, impairs daytime function, including mood and cognitive functions (Martin, Brander, Deary, & Douglas, 1999; Spiegel, Leproult, & Van Cauter, 1999). Sleep deprivation can cause deficits in cognitive and psychomotor performance that is equal to deficits occurring with legal levels of alcohol intoxication. Performances after 17 hours of being awake were similar to performances with a blood alcohol level of 0.05%, and after 24 hours of wakefulness, performances declined to levels similar to those of people with blood alcohol levels of 0.10% (Dawson & Reid, 1997). Verbal learning is particularly impaired after sleep deprivation (Drummond et al., 2000). The phase of the menstrual cycle affects the amount of cognitive impairment during sleep deprivation, with lower overall functioning seen during the premenstrual (i.e., follicular) phase (Wright & Badia, 1999). Because sleep deprivation has a negative effect on cognition and ability to learn, the informed consent process can be compromised either by the person who is providing the explanation and obtaining the consent or by the person who is valiantly trying to understand and assimilate the material after a sleepless night.

Respiratory Disorders and Hypoxia

Some degree of hypoxia frequently accompanies many disease processes and has been shown to be associated with general difficulty in thinking. This phenomenon seems to be true of both patients and healthy individuals. To separate the effect of hypoxia from the possible effects of anesthesia, Noble et al. (1993) examined the effect of lowered oxygen saturations (M = 78%) resulting from reduced fraction of inspired oxygen (Fi [O.sub.2]) on cognition of healthy volunteers. They found that even with no known pathology, these participants had significant reduction in ability to perform various timed psychological tests and worsened reaction times. Petiet et al. (1988) examined cognition in another group of healthy volunteers--female mountain climbers at extremely high altitudes (17,300-20,500 ft)--and found similar results: that complex abstract reasoning and word-finding ability were diminished. The climbers' difficulty with language persisted after their return to sea level.

A Dutch group of pulmonologists studied selective attention (necessary for accident-free driving and other instrumental activities of daily living) in healthy controls and a group of patients with chronic obstructive pulmonary disease (COPD) experiencing nocturnal hypoxemia with reduced oxygen saturations at night as low as 68%. They found that the patient group performed significantly less well on their estimate of selective attention (Vos et al., 1995). Oxygen desaturations during sleep that occur with sleep apnea/hypopnea syndrome are likewise associated with daytime decrements in cognitive performance (Cheshire, Engleman, Deary, Shapiro, & Douglas, 1992). Treatment with supplemental oxygen, seems to help (Hjalmarsen et al., 1999), as does aerobic fitness (Etnier et al., 1999). Because nighttime desaturations can occur as long as 96 hours after surgery (Noble et al., 1993), some cognitive slowing may exist for at least that time. Careful consideration of a person's general functioning is warranted if he or she is at risk for hypoxic episodes before he or she is asked for consent or data are collected. Perhaps waiting until oxygenation has been improved might be helpful. Providing other supportive strategies delineated later in this article may be helpful.


Either hypoglycemia or hyperglycemia can lead to cognitive impairment. Park (2001) reported that glucose metabolism in the hippocampus, a region of the brain critical to formation of memory (Kandel, Schwartz, & Jessell, 1995) is increased in response to exogenous insulin exposure; thus, hypoinsulinemia may also affect cognition and memory. Zelinski et al. (1998) reported that older people with diabetes demonstrated impaired recall and poorer overall performance when compared with people who were not diabetic.

Judgment also can be compromised. A group of patients with type 1 diabetes were found to make serious errors in estimating their blood glucose level (and thus errors in need to test and potentially treat themselves) when their blood sugar levels were at about 70 mg/dl (Weinger et al., 1999). They also found that women and, surprisingly, young adults were more conservative in their estimated ability to drive with low-blood-sugar levels than men. Certainly not all who are diabetic will have impaired cognition; however, many may experience some cognitive impairment from time to time, depending on the stability of their disease process. Asking for consent to treat or to participate in a research project during a period of impaired diabetic control may lead to misunderstandings about the nature of the project or treatment.


Pain is common among patients and research participants and affects thinking. Chronic pain is associated with reduced ability to attend to stimuli and reduced speed of processing (Hart, Martelli, & Zasler, 2000). Pain has been shown to reduce reaction times among cancer patients, even those who are not taking opioids (Sjogren et al., 2000). Postoperative pain was found to be associated with cognitive slowing in patients who have undergone lumbar spine surgery (Heyer et al., 2000). After studying another group with low back pain, Luoto et al. (1999) hypothesized that chronic pain interferes with short-term memory. Relief of pain with nonopioid analgesics (e.g., treatment of migraine with sumatriptan) may improve cognitive functioning (Farmer et al., 2000). However, the use of opioid pain medications in Sjogren's study was associated with lower scores on two of the neuropsychological tests--the controlled oral word association test and the Rey complex figures test. This suggests that perhaps both pain and treatment of pain with opioids may negatively affect a person's ability to process information in a consent form or questionnaire. Extra time may be needed, and information should be presented at times when pain intensity is reduced and sedation is not at its peak.

Neurological Disorders

Because much neuropathology affects the brain, cognitive slowing is associated with many common neurological conditions. The following list is not exhaustive, but reflects conditions that are frequently encountered.

Epilepsy. Seizure disorders may alter cognitive function and therefore put those experiencing it at risk for difficulty in making informed decisions. Binnie (2001) noted that the following factors could potentially cause cognitive impairment among those with seizure disorders:

* the pathophysiology underlying the seizure disorder or occurring as a result of the seizure disorder

* the occurrence of more than one seizure type in an individual

* educational deprivation resulting from social stigma or from the seizures themselves

* disruption of sleep

* subclinical discharges (those electrical discharges that are not associated with overt behavioral or movement disorders)

* antiepileptic drugs (AEDs).

AEDs have been associated with mental slowing (Aldenkamp, 2001). Some (phenobarbital and diphenylhydantoin) seem worse than others, affecting short-term memory and speed of mental processing particularly. Untreated seizures also have been associated with reduced mental flexibility and difficulty concentrating (Pullianainen, Kuikka, & Jokelainen, 2000). Pullianainen et al. did not report cognitive findings in their subject group after having started them on AED therapy, and it would be interesting to know whether interrupting the electrical dysfunction would improve mental functioning in that group. Binnie (2001) noted that there is a complex interaction between cognition and occurrence of epileptiform discharges; transitory cognitive impairment is associated with an interictal epileptiform spike. Further, some mental challenges seem to increase the epileptiform discharges, whereas other tasks seemed to suppress the discharges. I have noted that sometimes those with long-standing epilepsy do not follow instructions in the expected manner. Thus, it behooves the clinician to be alert and provide extra care in providing explanations and obtaining consent from this population. If someone appears suddenly slower in responding or understanding, wait a few minutes and try again.

Parkinson's disease. For many years neuroscience clinicians have noted that some people with Parkinson's disease (PD) have cognitive impairment, with recent estimates reflecting a prevalence of more than 40% (Hobson & Meara, 1999). In addition, hallucinations and delusions occur among those with PD (Aarsland, Larsen, Cummings, & Laake, 1999). Recently, Dymek, Atchison, Harrell and Marson (2001) have shown that PD patients have cognitive impairment on a variety of measures of executive function, including a relatively elementary task estimating ability to communicate a treatment choice. They were able, however, to make a choice if only one of the choices was reasonable and all others unreasonable (Dymek et al.). Unfortunately, in real treatment decisions, two choices may seem quite reasonable, leading to impaired decision making.

Multiple sclerosis. Historically, people with multiple sclerosis (MS) were described as having some degree of cognitive or emotional incapacity, in that many seemed euphoric in the face of rather striking physical disability (la belle indifference). Recent estimates have confirmed the presence of cognitive disability in up to as many as 65% of people with MS (Rao, 1995), with memory impairment, attention, executive functions, visuospatial perception, and speed of information processing being more affected than general intelligence, language, and short-term memory. Foong et al. (1998) found that some of the cognitive impairment evident just following an acute exacerbation of the disease may clear in about 6 weeks.

More careful investigation of the affective aspects of MS, however, has revealed that euphoria is not a hallmark of MS and is not even a common symptom. Depression is far more common and has more effect on quality of life (Kesselring & Klement, 2001). People with MS may however, have rapidly changing expressions of emotion, which may not reflect the emotions they are experiencing (Kesselring & Klement). For those with MS, the timing of the consent or the collection of data may make a difference in ability to understand and process information as well as energy to complete the tasks.

Stroke. Cognitive disability is very prevalent following stroke, with estimates of 43.9% in one study (Lawrence et al., 2001) and nearly 30% in another (Henon et al., 2001). Stroke also commonly affects either the ability to process language or to maintain orientation to spatial stimuli. Those who have experienced several strokes may have difficulty with both. Many instruments used to estimate cognitive impairment after stroke are problematic in that the instruments may have been developed for those with Alzheimer's disease and therefore the particular disabilities of stroke survivors (language and spatial orientation) may be confounded with cognitive decline. Some instruments may rely heavily on literacy and numeracy skills (e.g., spelling "world" backward or serial 7s) and therefore may not be appropriate for several populations, including those with stroke or people with low educational attainment. Recently, de Koning, Dippel, van Kooten, and Koudstaal (2000) published a short screening instrument for dementia following stroke that avoids many of the pitfalls of the Mini-Mental State Examination (MMSE). It asks for general information, recognition of items from memory, visual recognition of common objects, and abstraction in addition to memory. Low scores on instruments such as the MMSE may not necessarily preclude a person from generally understanding the tasks and giving consent. My experience with stroke populations leads me to believe that only very dense aphasia is a bar to understanding the requirements for a study and giving consent.

Strategies for Providing Information to Impaired' Populations

Many people with documented cognitive impairment are able to make reasonable choices about treatment options (Dymek et al., 2001). All people therefore must be given the opportunity to make a choice about treatment or participation in a research project. Even in circumstances in which responses cannot be determined or in which the person has been legally declared not competent to make decisions for himself or herself, all information must be given, and the person must be given the opportunity to assent to the proposed protocol.

Many people with mild to moderate cognitive impairment have not been declared incompetent. Even though their impairment does not interfere with enjoyment of life and may not be obvious to any but the most skilled observer, their impairment could interfere with the consent process or data acquisition. Much of the language that health professionals use has little meaning to most people, and healthcare professionals tend to be in a hurry, to rush people. Toedter et al. (1995) noted that stroke survivors' responses to standardized instruments may not be reliable because of their difficulty understanding items or confusion about the appropriate response. However, even those with moderate cognitive impairment are able to be consistent in their responses to questions (Feinberg & Whitlatch, 2001). The issue therefore seems to be whether explanations that people can understand and remember can be provided. Specific suggestions follow.


Select the time and place if possible. A calm distraction-free environment is more conducive to understanding unfamiliar or complex material for all people, and it is especially important for those who may have cognitive slowing or acquire all information through listening. Try to ensure that the person is not distracted by physical discomfort.

Don't hurry. Providing information in a meaningful way to those who may have some cognitive impairment requires that the information be presented at a speed consistent with their speed of mental processing.

Limit data collection sessions to 2 hours--less if possible. Fatigue is common among those with chronic disease and can take a toll on mental processing and therefore on comprehension and quality of data. If necessary, data collection might be broken into shorter sessions.

Consider presenting information verbally and in written form simultaneously. This may improve comprehension for some people and is necessary for those with low literacy. Ask before using this strategy. It may annoy some people, resulting in reduced comprehension. In addition, I have used a folded paper or ruler under each line as it is read while sitting next to the person. This helps keep the information from adjacent lines of type separate in the view of the patient. Slow the pace; read slowly. This strategy works well with those who have some expressive aphasia. It also helps achieve valid data from those with right hemisphere stroke who may select one answer verbally and mark another if responding to a Likert-type scale.

Format of Consent Form or Instruments

Use easy-to-read fonts in a large typeface. Arial or Times New Roman seems to be easy for those with brain impairment to read. The type should be at least 14 points. Morrow, Leirer, Andrassy, Hier, and Menard (1998) investigated the effectiveness of different formats for medication instructions and found that presenting information in a list format seemed easier for people to learn and retain than the more standard paragraph format. This finding may have implications for consent forms. Using headers to categorize information did not seem to make the information easier to retain.

Many questionnaires are constructed using a stem, followed by several adjectives. For example, "In the last week I felt ..." followed by as many as 50 items. In a new questionnaire (or an existing questionnaire that is intended for use with a cognitively impaired population), consider using a simple declarative sentence for each item. Those with cognitive impairment tend to have trouble remembering the stem, but can respond successfully to a short sentence.

Visual analog scales or numeric scales have been used successfully with patient groups who are not literate (Martinez et al., 2000). However, horizontal visual analog scales may give inaccurate data if used with people with dense hemispatial neglect, common after right hemisphere stroke.

Simplify Language

Keep the language as simple as possible. Remember that the person may have a reading level that is below the high school reading level, may be functioning in a second language, or may have neural language impairment. These conditions will affect a person's ability to understand. When possible, frame explanations in words that are familiar to the target audience. I have had participants ask the meaning of short words such as "tense" as well as longer words such as "enthusiastic." It's fair to tell them the meaning of the word. If a four-letter word will do, use it. "Take part in" is shorter and easier to understand than "participate in." "Every cloud has a silver lining" would be easier to understand than "I'm a believer in the idea that every cloud has a silver lining."

Address Only One Idea at a Time

Presenting information a little at a time, rather than in a large package, may be a useful strategy (Mukherjee & Shah, 2001). Those with cognitive deficits may become very concrete in their interpretation of information. Include only one idea in an item. Asking "Do you feel tense or wound up?" may elicit a question as to whether they are "tense" or whether they feel "wound up."

Look for Evidence of Comprehension

Unfortunately, people may be hesitant to ask questions if they do not understand something. Encourage questions. Rephrase instructions if someone looks puzzled. Try to answer the question that was intended. Even those who are intact may have difficulty expressing themselves. The patient's mother who asked, "But doctor, how will you do the operation?" (a craniotomy) was not informed by the response, "Of course, I'll turn a flap in the standard manner." Further probes elicited the real question: "Will you cut her hair?"


Giving informed consent to treatment or to participation in a research study is a right. The process of becoming informed can be negatively influenced by a variety of sociological or physiological conditions associated with mental slowing, difficulty with language, or lack of energy. These conditions (e.g., pain, sleep deprivation and fatigue, hypoxia, derangements of glucose metabolism, and various neurological disorders) need not exclude people from participating in research projects or necessitate consent from a surrogate or proxy. Research demonstrates that even those with documented cognitive impairment can make consistent choices and can choose a reasonable alternative over an unreasonable alternative. However, this group of people may require special help to understand treatment options, requirements of participation in a study, or instructions for care. Simplifying language, simplifying the environment, and using large type and straightforward formatting will help this important group of people understand and consent to treatment options or research endeavors.


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Questions or comments about this article may be directed to: Anne M. Williams, PhD RN, School of Nursing, University of Alabama at Birmingham, 1530 3rd Avenue S., Birmingham, AL 35294-1210. She is an assistant professor in the School of Nursing at the University of Alabama.
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Author:Williams, Anne M.
Publication:Journal of Neuroscience Nursing
Geographic Code:1USA
Date:Aug 1, 2002
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