Humans advanced from hunter-gatherers following the retreat of the pleistocene ice age 10,000 BC, but it wasn’t until the Neolithic revolution 5000–8000 BC where the development of tools allowed for planned agriculture. This led to crop cultivation and increased the diversity of food materials available, ultimately leading to the concept of recipes to include bread, beer, and soup by about 4000 BC. We have since come to use food to define our cultures, and the act of sitting at a meal with family, friends, and business relationships helps determine our pleasures and success in life. Thus, the impact of impaired swallowing (dysphagia) has profound quality-of-life as well as the expected nutritional consequences.
There are new challenges as we enter an era beyond the agricultural and industrial revolutions. Technological advances are facilitating increased life expectancy, where there is a growing aging population with increased medical problems. Oropharyngeal dysphagia is present in as many as 35% of the population older than 75, as associated with muscle atrophy, cognitive decline, and increased aspiration risk. While the world population is expected to have 1 billion people older than 65 years by 2020, this number is forecasted to grow to 2 billion by 2050. People are also living to older ages, so the prevalence and impact of dysphagia are also expected to increase.
Our fast-paced lifestyles have shifted commitments from standard meal times, and there’s an associated increased likelihood of gastroesophageal reflux (GERD), which can contribute to dysphagia. In one 12-year period from 1990 to 2001, there was a documented four-fold increase in visits to physicians in the United States for GERD, emphasizing its significant epidemiologic impact. Food supplies and sources are increasingly diverse, not only the types of products available through modern transportation that overcomes the historic seasonal limitations but also the increasing array of natural and synthetic ingredients. These issues offer a mixed blessing, diminishing a holistic natural existence, yet offering an amazing set of opportunities to address nutrition.
The consequences of dysphagia are also staggering. Long disqualified as an unfortunate complication of aging, stoke, and other degenerative illnesses, dysphagia affects both nutrition and quality of life. The idea of a family member dependent on enteral feeding when others are eating is depressing to them and counters their natural drives to eat. Social isolation is another severe consequence. And costs to the health care system are significant. In a study using the National Hospital Discharge Survey from 2005 to 2006, the presence of dysphagia was shown to be associated with a 40% increased length of stay (4 days compared to 2.4 days hospitalization in patients without dysphagia), with greater than $500 million of direct costs annually. Mortality was 13 times higher in rehabilitation patients with dysphagia compared to those with no dysphagia, and 1.8 to 2.6 times higher during hospitalizations associated with cardiac dysrhythmias and atherosclerosis, respectively. Also, the rate of dysphagia was double (0.73% of all hospitalizations) in the age group 75 years and older compared to 45 to 64 years old.
Our traditional understanding of the swallowing mechanism is changing. In the following list, there is renewed appreciation for central neurologic control, and the role of the larynx:
- 1.
Oral preparatory phase : mastication and tongue manipulation of food, soft palate seal against the posterior tongue
- 2.
Oral transport phase : tongue thrust and propulsion of the bolus to the oropharynx
- 3.
Pharyngeal phase : pharyngeal constrictor contraction with peristalsis, laryngeal and pharyngeal elevation, false vocal fold closure, cricopharyngeus muscle relaxation
- 4.
Esophageal phase : cricopharyngeus muscle contraction following passage of the bolus, esophageal peristalsis, secondary peristalsis. This phase should also address lower esophageal relaxation and competence (to be able to relax, or conversely, to prevent regurgitation)
- 5.
Central neurologic control : brainstem deglutition reflexes, coordination with cessation of respiration, nutritional drive, urge for satiety, cognitive awareness of food bolus, social influence
- 6.
Laryngeal roles : sensation of the bolus aids aspiration protection, and the cricopharyngeus is a shared muscle with the pharynx and larynx. Also, when there is penetration or microaspiration, glottal closure is essential for a competent cough reflex that produces accelerative flow for expulsion from the lungs rather than linear flow.
Dysphagia can be classified by the location, generally oral/pharyngeal versus esophageal phases. Also, the basic etiology of the dysphagia may be considered to be neuromuscular or obstructive. Some specific medical disorders of these divisions are listed in Table 1 . The most common etiologies of dysphagia in different age groups also help the clinician diagnose the underlying causes of dysphagia. In this classification, infancy is associated with neurodevelopmental delay; childhood and adolescence is associated with pharyngitis; young adult to middle age is associated predominantly with GERD; and older adults are at significantly higher risk because of medical comorbidities and neurodegenerative disease.
