There is usually no pain in the early stages... ALS does not usually affect bladder control or the senses.... Causes of ALS ALS affects the nerve cells that control voluntary muscle movements such as walking and talking (motor neurons). The disease causes motor neurons to gradually wear out and then die. Motor neurons extend from the brain to the spinal cord to muscles throughout the body.. When motor neurons are damaged, they stop sending messages to the muscles, so the muscles can't work.. The cause is unknown.... Researchers continue to investigate possible causes of ALS.... Most theories focus on the complex interaction between genetic and environmental factors.... Risk factors Proven risk factors for ALS include: - Heredity - age - Gender - Genetics - Smoking - Exposure to environmental toxins - Risky jobs ### Heredity 5-10% of people with ALS have inherited it (familial ALS).. The risk of developing ALS increases with age and is most common in the 40s to 60s.. Before age 65, men are slightly more likely to develop ALS than women.. This gender difference disappears after age 70.. ### Genetics Some studies that looked at the entire human genome found many similarities in the genetic changes in people with familial ALS and some people with non-hereditary ALS.. These genetic changes may predispose people to ALS.. Smoking is the only possible environmental risk factor for ALS.... The risk seems to be greater for women, especially after menopause. Some evidence suggests that exposure to lead or other substances at work or at home may be linked to ALS.. Many studies have been conducted, but no single agent or chemical has been consistently linked to ALS.. These include exposure to certain metals or chemicals, traumatic injuries, viral infections, and vigorous activity... Complications of ALS As the disease progresses, ALS causes the following complications: - Respiratory problems - Speech problems - Eating problems - Dementia ### Respiratory problems Over time, ALS paralyzes the muscles used for breathing.. In this condition, you may need a device to help you breathe at night, similar to what a person with sleep apnea might use.. For example, you may be given a BiPAP machine (BiPAP) to help you breathe at night.. trachea) to use a mask that inflates their lungs full time.... The most common cause of death in people with ALS is failure. It is breathable.... On average, death occurs within 3 to 5 years after the onset of symptoms.