IgG4-related disease and environment

What the research found.

• One study asked 95 Mexican patients with IgG4-related disease about their work and their exposures. Of those, 78 had paid work and 31.6 percent reported an exposure at work. Work exposure was associated with one form of the disease at an odds ratio of 3.5, on an interval from 1.08 to 11.36.

  Martin-Nares and colleagues, Clinical and Experimental Rheumatology, 2024

• A history of smoking was associated with more lung involvement in that study. The odds ratio was 3.2, with the true value ranging from 1.1 to 9.4. Not one person in that study was followed from smoking to illness, so what it reports is a link rather than a cause.

  Martin-Nares and colleagues, Clinical and Experimental Rheumatology, 2024

• That study also asked about cooking and heating with wood or coal indoors. The exposure was associated with a different form of the disease, at an odds ratio of 2.6 from 1.03 to 6.9. It was much commoner in blue-collar workers, at 64.3 percent against 19 percent.

  Martin-Nares and colleagues, Clinical and Experimental Rheumatology, 2024

• One review reports that IgG4-related disease affects at least 1 person in every 100,000 people. Most of them are diagnosed after the age of 50. The ratio of men to women is about 3 to 1, and those three facts are the background the rest of this page is against.

  Grasso and colleagues, Current Environmental Health Reports, 2023

• That review covers a case-control study of 90 patients and 270 controls. Asbestos exposure raised the risk of one condition in this family, at odds ratios ranging from 2.46 to 7.07. Its own authors call the asbestos link recently suggested and in need of more structured study.

  Grasso and colleagues, Current Environmental Health Reports, 2023

Two studies, and what they can do

This site holds two sources on the environment in IgG4-related disease, which is the thinnest environmental base of any disease covered here. Both of them are worth reading and neither of them is strong. That combination is what the rest of this page has to work with, and it's stated up front rather than buried.

The larger of the two is a study of 95 Mexican patients with the diagnosis. It asked each of them about their work history, their exposures, their smoking, and whether they cooked or heated their homes with wood or coal. Then it looked at which of those exposures was associated with which features of the disease.

The second source is a review rather than a study of its own. It gathers what has been published on environmental and occupational triggers, with a particular focus on asbestos, and it reports figures from the studies it covers rather than pooling them. That difference changes how much weight any figure taken out of it can hold.

Neither of the two followed anybody forward in time at all. Both of them looked at people who already had the disease and then asked them about their past, which is a design with a known weakness. That single fact decides what every figure below this can mean.

Work

Of the 95 patients in that study, 78 had paid work at the time it was done. Sixty-three of those did white-collar work and 15 did blue-collar work, so this is mostly a study of office and professional jobs. That's worth knowing before any of the occupational figures below it.

Occupational exposure of some kind was reported by 31.6 percent of the group. That exposure was associated with one form of the disease, at an odds ratio of 3.5, where the true value ranges from 1.08 to 11.36. Look at that interval before you look at the number in front of it.

It ranges from barely above 1 to more than eleven, which means very few people were in each of the groups being compared. An interval that wide is a question rather than an answer to one. It's the shape that a study of 95 people tends to produce.

One result in that study goes against what most people would expect. White-collar workers had more lung involvement than blue-collar workers, at 29 percent against 7.1 percent, at P equals 0.02. Pancreas and bile duct involvement was no commoner in the blue-collar group than in the other one.

Smoking

A history of smoking was associated with more lung involvement in those same 95 patients, which is the third of the three findings here. The odds ratio came out at 3.2, from 1.1 to 9.4. That's a link rather than a demonstrated cause, and the distinction recurs through the whole of this page.

The study asked about smoking after the disease was already there, and not one person in it was followed forward from smoking to illness. So the direction of that link is as open as the direction of everything else reported here. Reading it the other way round would fit the data just as well.

Smoking is still worth raising with your team, and the reasons for doing that reach well beyond this disease entirely. They don't depend on this figure holding up under a larger study. That's the useful thing about them, and it's why the advice doesn't change.

Cooking and heating with wood or coal

The study asked about burning wood or coal indoors, which it calls biomass fuel. That exposure was associated with a different form of the disease, at an odds ratio of 2.6, where the true value ranges from 1.03 to 6.9. It was also much commoner among blue-collar workers, at 64.3 percent against 19 percent.

So this exposure travels closely with the kind of work people do for a living. That makes the two of them very hard to separate in a study of 95 people, however carefully it was done. A finding about fuel could be a finding about occupation wearing different clothes.

The study can't tell you which of those two it found, and neither can this page. What it can do is put the figure in front of you with its interval attached to it. Reading both of those together is the whole skill here.

Asbestos

One review here covers a case-control study of 90 patients and 270 controls. Asbestos exposure raised the risk of one condition in this family of diseases, at odds ratios ranging from 2.46 to 7.07. That's a wide range out of one single study rather than a pooled estimate from several of them.

The review's own authors describe that link in careful words, and their particular choice of words is worth noticing. They call it recently suggested, and they say it needs more structured study. That's their wording rather than a hedge added here by anybody on this site.

The same review reports three background facts that are worth having in mind before any of that. This disease affects at least 1 person in every 100,000, and most of the people who have it are diagnosed after the age of 50. The ratio of men to women is about 3 to 1.

What this evidence can't tell you

Both studies looked at one moment in time, and that's the limit recurring through the whole of this page. It's worth understanding before you get to the numbers themselves. Everything else on this page follows from that one fact about the design.

A study that asks people with a disease about their past cannot say which of the two came first. It also depends on what people remember, and people with a new diagnosis tend to search their own history for causes. That's recall bias, and this study design is where it bites hardest of all.

No study here removed an exposure from anybody, and not one of them followed anyone forward in time. So nothing on this page can say what cutting an exposure would do to a disease you already have. That's a question the research hasn't answered rather than a negative finding.

What the figures on this page are really good for is a conversation with the people who are treating you. Tell your team what you did for work and what you were around. That information may well be useful to them, and it costs you nothing at all to give it.

Common misconceptions.

Cautions specific to this condition.

• Tell your team what you do and what you did for work. One study found work exposure reported by 31.6 percent of its patients and linked to one form of the disease.
• Mention cooking or heating with wood or coal if it applies to you. It was associated with a different form of the disease in that study.
• Read every interval on this page before the number in front of it. Three of them range from just above 1 to several times the estimate.
• Read no part of this as a cause. Both studies looked at one moment in time and neither can say which came first.
• Don't let exposure worry crowd out your treatment. The one trial this site holds in this disease tested a drug, not an exposure.
• Ask your team which form of the disease you have. These findings sort people by form, so the question decides which of them applies to you.

Questions patients ask.