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If you’re feeling a bit brain-fogged , you might not be wrong to blame it on the heat. Several summers back, researchers in Boston studied young adults living in college dorm rooms during a heat wave. Some had central AC and slept at a cool 71 degrees Fahrenheit. Others slept in rooms without air-conditioning, where the temperature hovered around 80 degrees. Each morning for nearly two weeks, the students took a few tests, administered on their cellphones..….Continue reading….
By: Allison Aubrey
Source: NPR
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Critics:
The hallmarks of dehydration include thirst and neurological changes such as headaches, general discomfort, loss of appetite, nausea, decreased urine volume (unless polyuria is the cause of dehydration), confusion, unexplained tiredness, purple fingernails, and seizures.
The symptoms of dehydration become increasingly severe with greater total body water loss. A body water loss of 1-2%, considered mild dehydration, is shown to impair cognitive performance. While in people over age 50, the body’s thirst sensation diminishes with age, a study found that there was no difference in fluid intake between young and old people.
Many older people have symptoms of dehydration. Dehydration contributes to morbidity in the elderly population, especially during conditions that promote insensible free water losses, such as hot weather. A Cochrane review on this subject defined water-loss dehydration as “people with serum osmolality of 295 mOsm/kg or more” and found that the main symptom in the elderly (people aged over 65) was fatigue.
Risk factors for dehydration include but are not limited to: exerting oneself in hot and humid weather, habitation at high altitudes, endurance athletics, elderly adults, infants, children and people living with chronic illnesses. Dehydration can also come as a side effect from many different types of drugs and medications.
In the elderly, blunted response to thirst or inadequate ability to access free water in the face of excess free water losses (especially hyperglycemia related) seem to be the main causes of dehydration. Excess free water or hypotonic water can leave the body in two ways – sensible loss such as osmotic diuresis, sweating, vomiting and diarrhea, and insensible water loss, occurring mainly through the skin and respiratory tract.
In humans, dehydration can be caused by a wide range of diseases and states that impair water homeostasis in the body. These occur primarily through either impaired thirst/water access or sodium excess. Dehydration occurs when water intake does not replace free water lost due to normal physiologic processes, including breathing, urination, perspiration, or other causes, including diarrhea, and vomiting.
Dehydration can be life-threatening when severe and lead to seizures or respiratory arrest, and also carries the risk of osmotic cerebral edema if rehydration is overly rapid. The term “dehydration” has sometimes been used incorrectly as a proxy for the separate, related condition of hypovolemia, which specifically refers to a decrease in volume of blood plasma.
The two are regulated through independent mechanisms in humans; the distinction is important in guiding treatment. The most effective treatment for minor dehydration is widely considered to be drinking water and reducing fluid loss. Plain water restores only the volume of the blood plasma, inhibiting the thirst mechanism before solute levels can be replenished.
Solid foods can contribute to replace fluid loss from vomiting and diarrhea. Urine concentration and frequency will return to normal as dehydration resolves. In some cases, correction of a dehydrated state is accomplished by the replenishment of necessary water and electrolytes (through oral rehydration therapy, or fluid replacement by intravenous therapy). As oral rehydration is less painful, non-invasive, inexpensive, and easier to provide, it is the treatment of choice for mild dehydration.
Solutions used for intravenous rehydration must be isotonic or hypertonic. Pure water injected into the veins will cause the breakdown (lysis) of red blood cells (erythrocytes). When fresh water is unavailable (e.g. at sea or in a desert), seawater or drinks with significant alcohol concentration will worsen dehydration.
Urine contains a lower solute concentration than seawater; this requires the kidneys to create more urine to remove the excess salt, causing more water to be lost than was consumed from seawater. If a person is dehydrated and taken to a medical facility, IVs can also be used.
For severe cases of dehydration where fainting, unconsciousness, or other severely inhibiting symptoms are present (the patient is incapable of standing upright or thinking clearly), emergency attention is required. Fluids containing a proper balance of replacement electrolytes are given orally or intravenously with continuing assessment of electrolyte status; complete resolution is normal in all but the most extreme cases.
Dehydration – Symptoms and causes”.
Acute and chronic effects of hydration status on health”.
Analysis in Nutrition Research
Hydration and Chronic Kidney Disease Progression: A Critical Review of the Evidence”.
The Hydration Equation: Update on Water Balance and Cognitive Performance”.
Volume depletion versus dehydration: how understanding the difference can guide therapy”.
Oxford Handbook of Clinical Examination and Practical Skills.
How much water should you drink?”.
Variation in human water turnover associated with environmental and lifestyle factors”
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