The prevalance of preschool children stuttering is about 2.5%, that is, about 1 in 40 young children now stutter. The incidence is about 5%, or 1 in 20 children stutter at some point in childhood. About 1% of adults stutter. 0.73%, or about one in 135 adults, was the figure found in a recent study. Studies in years past claimed that some countries had higher or lower rates of stuttering, or that some cultures had no stutterers at all.

Nobody knows that for sure. Stuttering is found in every language and every country in the world, and evidence of stuttering is found in several very old documents. There is even an example of a speech problem in Egyptian symbols called hieroglyphics. As you can see, the picture shows a person trying to speak but the speaking gets blocked by what looks like walls. Maybe this symbol was showing stuttering.

Stuttering is a speech disorder in which the flow of speech is disrupted by involuntary repetitions and prolongations of sounds, syllables, words or phrases; and involuntary silent pauses or blocks in which the stutterer is unable to produce sounds. Stuttering is known as stammering in the United Kingdom, and is sometimes misspelled studdering.

IBS affects between 25 and 55 million people in theUnited States and results in 2.5 to 3.5 million yearly visits to physicians. Approximately 20 to 40 percent of all visits to gastroenterologists are due to IBS symptoms. IBS symptoms affects men and women of all ages and of all races. The prevalence of IBS in the general population of Western countries varies from 6 to 22%. IBS affects 14-24% of women and 5-19% of men.

In 2003, a detailed, federally supported study was published on the prevalence of autism spectrum conditions among children aged 3 to 10 years in metropolitan Atlanta. Using 1996 data, that study showed the prevalence for autism was 3.4 per 1000, with a male-female ratio of 4 to 1. The study did not show a major increase in autism compared to studies done in the 1980s and early 1990s.

The term "incidence" refers to the number of newly diagnosed cases of a disease occurring in a specific population during a specific time period. The incidence rate is the number of newly diagnosed cases in a specific population during a specific time period per "x" number of people; usually the time period is one year and "x" number of people is 100,000. Such an incidence rate is "crude", is not age adjusted (see #11 below) and therefore cannot be used to compare different populations.

Texas Cancer Information expects to add incidence data in the fall of 2007. There is currently limited incidence and survival data available in the on-line publication of Texas Cancer Facts & Figures 2004 , a publication made possible through the collaborative efforts of the American Cancer Society, Texas Division, Inc.

Studies suggest the prevalence is somewhere between 1 in 200 - 500. In recent years there has been a large increase in the number of children diagnosed with ASD, particularly those in the high functioning category. This is probably due to a broadening of the criteria for diagnosis, and better diagnostics methods enabling detection at a very young age.

Studies have shown that asthma is more common in African Americans than in Caucasians, but experts are not sure this is related to race. It could be that higher numbers of African Americans live in large urban areas, which is known to be a risk factor because of the higher levels of pollution and other asthma triggers.

In 1999–2000, an estimated 15% of children and adolescents aged 6–19 years were overweight, defined as a body mass index for age and sex at or above the 95th percentile of the CDC growth charts.

Some studies indicate that diagnosable dissociation occurs in approximately two to three percent of the general population. Other studies have estimated a prevalence rate of 10% for all dissociative disorders in the general population (e.g., Loewenstein, 1994). Dissociation may exist in either acute or chronic forms. Immediately following severe trauma, the incidence of dissociative phenomena is remarkably high.

More and more women attending antenatal clinics are testing HIV-positive thereby increasing the chances of perinatal transmission. More than 1% of the antenatal mothers in the States of Maharashtra, Tamil Nadu, Andhra Pradesh, Karnataka, Nagaland and Manipur are infected with HIV.