Namaste Care Program
Named after the Hindu term meaning “to honor the spirit within,” this 7-day-a-week program for people with dementia designates space to help create a safe and comforting environment for residents, families, and staff. It is designed to bring pleasure to people and can make receiving and giving of care enjoyable by modifying care strategies.

Narcotics
Drugs that in moderate doses dull the senses, relieve pain, and induce sleep but in excessive doses cause stupor, coma, or convulsions.

Narrative review
A review article (eg, a typical book chapter) that is not conducted using methods to minimize bias (in contrast to a systematic review).

Natural history
As distinct from prognosis, natural history refers to the possible consequences and outcomes of a disease or condition and the frequency with which they can be expected to occur when the disease condition is untreated.

Nausea
Discomfort and distress manifested as the urge to vomit.

Neary criteria
Criteria for the diagnosis of frontotemporal dementia, including the following clinical diagnostic features: insidious onset and gradual progression, early decline in social interpersonal conduct, early emotional blunting, early loss of insight. Supportive diagnostic features include decline in personal hygiene, mental rigidity, distractibility, aspontaneity, and economy of speech. For more information, see the following article for the criteria: Neary D, Snowden JS, Gustafson L, et al. Frontotemporal lobar degeneration: a consensus on clinical diagnostic criteria. Neurology. 1998;51(6):1546-1554. [PMID: 9855500]

Negative effect
As clinical studies accumulate, it is more common for effects to shrink than to increase. Negative effects are smaller or less dramatic than effects from previous studies.

Negative predictive value
See Predictive value.

Negative studies
Studies in which the authors have concluded that the comparison groups do not differ statistically in the variables of interest. Research results that fail to support the researchers’ hypotheses.

Neural network
The application of nonlinear statistics to pattern-recognition problems. Neural networks can be used to develop clinical prediction rules. The technique identifies those predictors most strongly associated with the outcome of interest that belong in a clinical prediction rule and those that can be omitted from the rule without loss of predictive power.

Neurogenic claudication
A symptom of lumbar spinal stenosis. Pain or other discomfort with walking or prolonged standing that radiates into one or both lower extremities and is typically relieved by rest or lumbar flexion.

Neurokinin type 1 (NK1) receptor selective antagonists
A class of medications with unique antidepressant, anxiolytic, and antiemetic properties used in the prevention of nausea and vomiting associated with cancer.

Neuropathic pain
A type of pain that is caused by damage to or dysfunction of the nervous system. Often treated with anticonvulsants, tricyclic antidepressants, local anesthetics, and other types of medications, in addition to opioids. As distinguished from nociceptive pain.

Neurotoxins
Proteins that have harmful effects on the nervous system.

Neutrophils
The most abundant type of white blood cells. They migrate toward the site of inflammation and are the predominant cells in pus.

New York Heart Association (NYHA) class
A method of classifying the extent of heart failure by assigning patients in 1 of 4 categories based on the degree to which their symptoms limit their physical activity: class I patients are those with no limitation on ordinary physical activity; class II are those with slight limitation of physical activity; class III are those with marked limitation of physical activity; and class IV are those unable to engage in any physical activity without discomfort or symptoms present at rest. For more information, see the following Web site for the classifications: http://www.americanheart.org/presenter.jhtml?identifier=1712.

N-methyl-D-aspartate (NMDA) receptor
A glutamate receptor that is the main molecular device for controlling synaptic plasticity and memory function.

Nociceptive pain
Pain resulting from tissue damage, usually treated with opioid medications. As distinguished from neuropathic pain.

N-of-1 randomized controlled trial
An experiment designed to determine the effect of an intervention or exposure on a single study participant. In one N-of-1 design, the patient undergoes pairs of treatment periods organized so that 1 period involves the use of the experimental treatment and 1 period involves the use of an alternate treatment or placebo. The patient and clinician are blinded, if possible, and outcomes are monitored. Treatment periods are replicated until the clinician and patient are convinced that the treatments are definitely different or definitely not different.

Nominal variable
A variable that can be classified into a category (eg, male or female sex); often called categorical varaible. A categorical variable may be nominal or ordinal. Categorical variables can be defined according to attributes without any associated order (eg, medical admission, elective surgery, or emergency surgery); these are called nominal variables. A categorical variable can also be defined according to attributes that are ordered (eg, height such as high, medium, or low); these are called ordinal variables.

Nomogram
Graphic scale facilitating calculation of a probability. The most-used nomogram in the evidence-based medicine world is one developed by Fagan to move from a pretest probability, through a likelihood ratio, to a posttest probability.

Nonadherent
Patients are nonadherent if they are not exposed to the full course of a study intervention (eg, most commonly, they do not take the prescribed dose or duration of a drug or they do not participate fully in the study program).

Noninvasive positive pressure ventilation
A type of ventilatory support that does not require mechanical intubation and can improve exercise tolerance and quality of life when combined with physical training in selected patients with advanced chronic obstructive pulmonary disease and neuromuscular disorders such as amyotrophic lateral sclerosis.

Nonrandomized controlled trial
In an nonrandomized controlled trial, it is difficult or impossible to assign participants to different study arms (interventions) by chance. These types of trials are subject to bias because of the inability to control for factors between groups that could affect outcomes.

Nottingham Prognostic Index
A tool used to determine prognosis after surgery for breast cancer.

Novalis Shaped Beam Surgery
See stereotactic radiotherapy.

Null hypothesis
In the hypothesis-testing framework, this is the starting hypothesis that the statistical test is designed to consider and possibly reject, which contends that there is no relationship between the variables under study.

Null result
A nonsignificant result; no statistically significant difference between groups.

Number needed to harm
The number of patients who, if they received the experimental intervention, would lead to one additional patient being harmed over a specific period of time. It is the inverse of the absolute risk increase (ARI), expressed as a percentage (100/ARI). See also Absolute risk increase.

Number needed to screen
The number of patients who would need to be screened to prevent one adverse event.

Number needed to treat
The number of patients who need to be treated over a specific period of time to achieve one additional good outcome. When discussing NNT, it is important to specify the intervention, its duration, and the desirable outcome. It is the inverse of the absolute risk reduction (ARR), expressed as a percentage (100/ARR). See also Absolute risk reduction.

Nursing homes
Privately or publicly operated residential establishments where personal and medical care is provided for people who are unable to adequately care for themselves.