5 ms·

Seems like childhood leukaemia would only be experienced by eldest children if this were so. You'd imagine that almost all children living with an older sibling

by harry8 8y ago

Seems like childhood leukaemia would only be experienced by eldest children if this were so. You'd imagine that almost all children living with an older sibling are exposed to the works to "prime their immune system" from birth. That seems like such a strong signal it would have been commented on, possibly named for it, and yet I've never heard of leukaemia as a oldest child disease. Obviously this is not my field and I have the cynicism of reading and hearing about cancer breakthroughs since before clickbait had a name.

triviatise 8y ago
from a random paper from 1995 https://academic.oup.com/jnci/article/89/13/939/2526258 https://academic.oup.com/jnci/article/89/13/939/2526258 << A total of 704 cases of childhood ALL were identified. Among 0-4 year olds, the relative risks (RRs) of ALL for birth order positions 1, 2, 3, and 4+ were 1.00 (reference), 0.85 (95% confidence interval [CI] = 0.68-1.07), 0.91 (95% CI = 0.66-1.25), and 0.57 (95% CI = 0.30-1.06), respectively ( P for trend = .09).>> <<Children born second or later in the birth order had an increased risk of AML (RR = 1.53; 95% CI = 1.01-2.32) compared with firstborns. >>
- ithilglin909 8y ago
  Exposure to siblings might not be helpful, since those children, particularly young ones, are probably subject to the same environmental factors/presence (or lack thereof) bacteria and viruses.
  - WhompingWindows 8y ago
    You may have misunderstood his rationale. The OP article suggests that kids need to have early infections and less clean environments in the first year, as later dirtiness can trigger a mutation that incurs leukemia. The parent comment says: well, if you have an older sibling, you should be more likely to be exposed to dirty stuff, since they're in/out of the house, picking up dirt, kissing dogs, getting sick from daycare, etc.
    - kevin_thibedeau 8y ago
      The mutation is already present. Per the article, the proposed trigger is an immune system that hasn't been desensitized to common environmental pathogens during early childhood.
- ravitation 8y ago
  There are a couple of cited studies in that paper that show different relationships between birth order and relative risk, but this specific study happens to indeed show an inverse relationship between relative risk and birth order. That second quote is about AML, which is a different form of leukemia than the one discussed in the paper published today.
paulirwin 8y ago
My younger brother died from ALL when he was 24, got it at 22. Although he was in his twenties, this was considered the "childhood" form of leukemia. Of course this is anecdotal, but because of my experience as the surviving eldest child, I happen to agree with you. But it's also entirely possible that he had less exposures than I did early in life, despite being the younger. Just one example off the top of my head, he was brought home after delivery to a different house than I was, a new construction at the time. I could also envision some repeat parents "learning" from their experiences with the first child such that the first child actually has more exposure. I do not particularly want to discuss this with my parents to determine if they could think of a reasoning though, lest I add to their survivor's guilt.
epmaybe 8y ago
I think there are too many confounding factors to make a strong claim either way. For example, the older a mother is the more risk there is of a child having downs syndrome, and that in turn is associated with higher risk of ALL/AML. So without considering other factors, you may be led to think that the younger siblings might have a higher risk (remember that the paper suggested that a first hit mutation may be required before the infection). My point is just that to test an epidemiologic hypothesis you have to really think about all the different confounding factors that could bias your results.

by harry8 8y ago

triviatise 8y ago

from a random paper from 1995 https://academic.oup.com/jnci/article/89/13/939/2526258 https://academic.oup.com/jnci/article/89/13/939/2526258 << A total of 704 cases of childhood ALL were identified. Among 0-4 year olds, the relative risks (RRs) of ALL for birth order positions 1, 2, 3, and 4+ were 1.00 (reference), 0.85 (95% confidence interval [CI] = 0.68-1.07), 0.91 (95% CI = 0.66-1.25), and 0.57 (95% CI = 0.30-1.06), respectively ( P for trend = .09).>> <<Children born second or later in the birth order had an increased risk of AML (RR = 1.53; 95% CI = 1.01-2.32) compared with firstborns. >>

ithilglin909 8y ago
Exposure to siblings might not be helpful, since those children, particularly young ones, are probably subject to the same environmental factors/presence (or lack thereof) bacteria and viruses.
- WhompingWindows 8y ago
  You may have misunderstood his rationale. The OP article suggests that kids need to have early infections and less clean environments in the first year, as later dirtiness can trigger a mutation that incurs leukemia. The parent comment says: well, if you have an older sibling, you should be more likely to be exposed to dirty stuff, since they're in/out of the house, picking up dirt, kissing dogs, getting sick from daycare, etc.
  - kevin_thibedeau 8y ago
    The mutation is already present. Per the article, the proposed trigger is an immune system that hasn't been desensitized to common environmental pathogens during early childhood.
ravitation 8y ago
There are a couple of cited studies in that paper that show different relationships between birth order and relative risk, but this specific study happens to indeed show an inverse relationship between relative risk and birth order. That second quote is about AML, which is a different form of leukemia than the one discussed in the paper published today.

paulirwin 8y ago

My younger brother died from ALL when he was 24, got it at 22. Although he was in his twenties, this was considered the "childhood" form of leukemia. Of course this is anecdotal, but because of my experience as the surviving eldest child, I happen to agree with you. But it's also entirely possible that he had less exposures than I did early in life, despite being the younger. Just one example off the top of my head, he was brought home after delivery to a different house than I was, a new construction at the time. I could also envision some repeat parents "learning" from their experiences with the first child such that the first child actually has more exposure. I do not particularly want to discuss this with my parents to determine if they could think of a reasoning though, lest I add to their survivor's guilt.

epmaybe 8y ago

I think there are too many confounding factors to make a strong claim either way. For example, the older a mother is the more risk there is of a child having downs syndrome, and that in turn is associated with higher risk of ALL/AML. So without considering other factors, you may be led to think that the younger siblings might have a higher risk (remember that the paper suggested that a first hit mutation may be required before the infection). My point is just that to test an epidemiologic hypothesis you have to really think about all the different confounding factors that could bias your results.