Incidence of Mesothelioma

Mesothelioma incidence describes how many new cases of this type of cancer have been diagnosed over a certain period of time. Incidence can be described in various populations, such as men, men over a certain age, or people in a geographic area, for instance. In the U.S., the incidence of mesothelioma in the population is thought to have already reached a peak and is now tapering off as regulations on the use of asbestos have been enacted and enforced. In most other countries around the world, the incidence is still rising.

Incidence is an important part of the study of the epidemiology of a disease, as is etiology or a description of the causes. Knowing where people are at a higher risk for mesothelioma, and what is causing the disease helps policy makers, researchers, and advocates take steps to prevent the incidence from rising and treat those who are already affected.

Mesothelioma Incidence by Age and Gender

By looking at incidence for certain diseases in different populations, researchers and others get a good idea of who is at risk and why. This also helps to pinpoint causes for a disease. According to the National Cancer Institute, in the U.S. the incidence of mesothelioma is consistently higher in men than in women. For both, the incidence peaked in the 1990s and has trended downward since then. In 2009 the incidence rate in men was about 1.8 per 100,000 and in women was about 0.9.

By age, incidence skews toward older Americans. Between 2008 and 2010 the incidence for men over 85 was 20.2, while for men between 55 and 64 it was only 2.1. For men between the ages of 75 and 84 the incidence was 6.8 and for those between 75 and 84 it was 17.2. For women, the incidence also rises with age, from 0.6 for ages 55 to 64 to 3.1 for women over 85.

The difference in incidence between men and women is usually explained by the fact that the major risk factor for mesothelioma is asbestos exposure. More men than women have worked in industries that put them at risk for being exposed to this mineral. By age, the incidence grows as the population gets older because mesothelioma has a long latency period. It can take decades from the first asbestos exposure to develop into a disease with symptoms.

Incidence of Mesothelioma by Job

Occupation is another major factor in the incidence of mesothelioma. The major cause of the cancer is asbestos exposure, so those people who worked in industries in which this mineral was used heavily are more likely to develop mesothelioma. The incidence of the cancer is higher in certain industries and this forms a pattern that points clearly to asbestos. It seems obvious now, but there was a time when it was not clear what caused mesothelioma. High incidence rates in industries with asbestos helped to clarify the role the mineral plays in this disease.

The Centers for Disease Control and Prevention (CDC) listed the industries in which the highest incidences of mesothelioma have been seen: construction workers, plumbers, pipefitters, steamfitters, janitors, cleaners, managers, workers in elementary schools, and workers in chemical industries. In the United Kingdom, where there are even higher rates of mesothelioma, occupations with the highest incidences include carpenters, joiners, construction workers, electricians, plumbers, metal workers, and heating and ventilating workers.

Incidence in Shipyards

Construction workers, pipefitters, steamfitters, plumbers, electricians, and others have higher risks of developing mesothelioma, particularly in one industry: ship building and repair. An epidemiological study of Virginia’s coastal shipyards found that the incidence of mesothelioma in workers there was four times higher than the national average incidence for men.

Understanding incidence in very specific industries, occupations, and regions, helps to pinpoint exactly where people are at risk of getting sick. By uncovering the high incidence of mesothelioma in Virginia shipyard workers, the researchers were able to provide the information that would lead to improved and safer working conditions and restrictions on the use of asbestos.

Incidence by Geography

Epidemiological studies that have investigated the incidence of mesothelioma around the country have found that certain areas are affected more than the rest of the country. New Jersey, for instance, has one of the highest incidences of mesothelioma. This can be explained by the Johns Manville Corporation, which ran an asbestos plant in Manville, New Jersey for decades. The incidence of mesothelioma among Manville workers was found to be 25 times higher than the national average.

Other areas with higher incidences of mesothelioma include the Seattle and Puget Sound area of Washington, Louisiana, California, Utah, Connecticut, New Mexico, and Detroit, Michigan. Some of these can be explained by the presence of asbestos mines, others by shipyards and other industries that used asbestos, like the automotive industry in Detroit. New York City is expected to see a raised incidence of mesothelioma in the coming decades as people exposed to dust from the World Trade Center attacks develop the disease.

Worldwide Incidence

For most of the U.S. the incidence of mesothelioma has peaked and is declining. This is thanks to the increased regulations placed on the use of asbestos and the increase in workplace safety regulations. Other countries are still trending upward, including some developed nations like the United Kingdom and Australia. The overall incidence for the entire world is still rising.

According to the World Health Organization, between 1994 and 2008 the mortality rate worldwide was 4.9 deaths from mesothelioma per million people. During that same time period, the average age of someone who died from mesothelioma was 70 and the ratio of men to women with the disease was 3.6 to one, trends that mirror those seen in the U.S.

Understanding the incidence of a disease like mesothelioma in the U.S. and around the world is important in understanding the disease itself. It helps to elucidate the causes of the disease. It also helps the people who are at risk by shedding light on risk factors, such as age, gender, occupation, industry, and geographical location.