Workplace link to 1 in 6 cases of adult asthma among UK baby boomers

The strongest evidence seems to be for jobs involving cleaning or cleaning agents, the research suggests.

The authors base their findings on the job histories up to the age of 42 of almost 7,500 British adults born in 1958, all of whom were taking part in the National Child Development Study, which is tracking the long term health of more than 11,000 people living in Britain.

Information about symptoms of asthma or wheezy bronchitis was collected at the ages of 7, 11, 16, 33 and 42 from 9,500 participants.

After excluding 2,000 who had these symptoms before the age of 16, the remainder were tested for sensitivity to allergens and their lung power between the ages of 42 to 45. Participants were also asked about their work history at the ages of 33 and 42.

Their exposure to compounds known to be associated with asthma was calculated using the Asthma Specific Job Exposure Matrix (ASJEM). This assigns workplace exposure to 18 different high risk antigens, environments, and respiratory irritants.

One in four were smokers by the age of 42, when the cumulative prevalence of asthma that had started in adulthood was 9%. Most (87%) were in employment at age 42, and over half (55%) had office jobs.

What is Adult-Onset Asthma?

When a doctor makes a diagnosis of asthma in people older than 20, it is known as adult-onset asthma.

Among those who may be more likely to get adult-onset asthma are:

  Women who are having hormonal changes, such as those who are pregnant or who are experiencing menopause
  Women who take estrogen following menopause for 10 years or longer
  People who have just had certain viruses or illnesses, such as a cold or flu
  People with allergies, especially to cats
  People who are exposed to environmental irritants, such as tobacco smoke, mold, dust, feather beds, or perfume. Irritants that bring on asthma symptoms are called “asthma triggers.” Asthma brought on by workplace triggers is called “occupational asthma.”


What is the Difference Between Childhood Asthma and Adult-Onset Asthma?

Adults tend to have lower lung capacity (the volume of air you are able to take in and forcibly exhale in one second) after middle age because of changes in muscles and stiffening of chest walls. This decreased capacity may cause doctors to miss the diagnosis of adult-onset asthma.

Around one in four participants had only ever worked in a job that was zero risk, according the ASJEM. Just under one in 10 (8%) had ever been exposed to high risk agents; while a further 28% had ever been exposed to low risk agents. Around one in three (34%) had ever been exposed to both.

There are many occupations that are thought to cause asthma, say the authors. And in this study the start of asthma in adulthood was clearly linked to 18 types of job, including farming, which more than quadrupled the risk, hairdressing, which almost doubled the risk, and printing, which tripled the risk.

Four of these 18 jobs were cleaning jobs, and a further three were likely to involve exposure to cleaning agents.

After taking account of factors likely to influence the results, people exposed to low risk agents were 20% more likely to have asthma diagnosed as an adult than those who had not been exposed to any risk.

Those exposed only to high risk agents were 53% more likely to have the condition, while those exposed to both types of agents were 34% more likely to do so.

The high risk agents implicated were flour, enzymes, cleaning/disinfectant products, metal and metal fumes, and textile production.

About 22 million Americans have asthma.

Gender
Before puberty, asthma occurs more often in males, but after adolescence, it is common in females. In adults with similar cases of actual airway obstruction, women are likely to report more severe symptoms than men.

Hormonal fluctuations or changes in hormone levels may play a role in the severity of asthma in women. Between 30 - 40% of women with asthma experience fluctuations in severity that are associated with their menstrual cycle. Some women first develop asthma during or shortly after pregnancy, while others first develop it around the time of menopause (perimenopause).

Race and Ethnicity
African-Americans have higher rates of asthma than Caucasians or other ethnic groups. They are also more likely to die of the disease. Ethnicity and genetics, however, are less likely to play a role in these differences than socioeconomic differences, such as having less access to optimal health care, and greater likelihood of living in an urban area (another asthma risk factor).

Obesity
Studies report a strong association between obesity and asthma. Evidence also suggests that people who are overweight (body mass index greater than 25) have more difficulty getting their asthma under control. Weight loss in anyone who is obese and has asthma or shortness of breath helps reduce airway obstruction and improve lung function.

Other Risk Factors

GERD. At least half of patients with asthma have gastroesophageal reflux disease (GERD), the cause of heartburn. It is not entirely clear which condition causes the other or whether they are both due to common factors. Treating GERD does not appear to improve asthma control.

Aspirin-Induced Asthma. About 10% of adults and fewer children have aspirin-induced asthma (AIA). With this condition, asthma gets worse when patients take aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs). AIA often develops after a viral infection. It is a particularly severe asthmatic condition, associated with many asthma-related hospitalizations. In about 5% of cases, aspirin is responsible for a syndrome that involves multiple attacks of asthma, sinusitis, and nasal congestion. Such patients also often have polyps (small benign growths) in the nasal passages. Patients with aspirin-induced asthma (AIA) should avoid aspirin and other NSAIDs, including ibuprofen (Advil) and naproxen (Aleve).

All in all, the authors calculated that 16% of adult onset asthma among those born in the late 1950s could be explained by the types of jobs held.

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Emma Dickinson
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44-020-738-36529
BMJ-British Medical Journal

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