A reduction of 0.1 pH units in human blood pH can have serious health repercussions, such as seizures, cardiac arrhythmia, or even coma (a process called acidosis). In addition, chronic exposure to low-grade acidosis is associated with bone loss, muscle weakness, and dementia. The body's ability to control acidity is through the buffering system, which consists mainly of alkaline substances like bicarbonate ions (HCO3−) that neutralize acids. When these buffers are used up, other substances are needed to maintain a healthy level of acidity in the blood. When carbon dioxide levels are high but the buffer systems are intact, this gas accumulates in the blood and causes the pH to fall. This occurs normally during sleep when the body produces more carbon dioxide; however, if the body is exposed to extreme temperatures, too much protein, or excessive amounts of alcohol, it may not be able to keep up with this extra production and the pH may begin to drop. Low blood pH has many implications for athletic performance. One study showed that athletes who suffered from acidosis performed worse on cognitive tests than those who had normal blood pH. Other studies have shown that people with acidosis experience greater fatigue during exercise and have difficulties regulating their body temperature.