7 ms·

"After adjusting for differences in age, sex, race, and ethnicity, the scientists found veterans from Camp Lejeune had a 70% higher rate of Parkinson’s disease

"After adjusting for differences in age, sex, race, and ethnicity, the scientists found veterans from Camp Lejeune had a 70% higher rate of Parkinson’s disease than the Camp Pendleton group." Why didn't they adjust for socioeconomic status? Wealthier people tend to be able to afford better medical care, live in healthier environments, eat healthier foods, etc. These could all be confounding factors, and a study like this should take them in to account.

calvinmorrison 3y ago
Presumably there's already known risk factors studied thoroughly for race, age, and sex. So they adjusted the numbers to account for that and their focus was on locality.
AdamN 3y ago
Alot of socioeconomic factors are baked into the above co-morbidities but anyway, is there a reason to think that veterans of two different marine camps have significantly different socioeconomic profiles from eachother?
- notakio 3y ago
  In this case (Lejeune vs Pendleton), there would likely not be a substantial socioeconomic difference between the collective backgrounds of Marines who did basic training at either one. But comparing either camp to OCS at Quantico would, in fact, show a pretty stark delineation between the socioeconomic backgrounds.
  - alistairSH 3y ago
    They looked at officer vs enlisted, which would cover any socioeconomic difference between basic vs OCS, no?
  - pmoriarty 3y ago
    There might not have been much difference between them at the time, but who knows how their lives went after their time there? Some might have wound up being relatively wealthy compared to the rest, and that could have influenced their long-term health. We won't know until we check.
hgsgm 3y ago
What happens when you end up accidentally controlling for exposure to the chemical?
bumby 3y ago
They were all active duty military and largely the same socio-economic cohort, and use the same medical system. Maybe they could draw a distinction between enlisted and commissioned, but my hunch is the disparity between raw numbers would lead to low statistical power. (This isn’t to say they originally came from the same socio-economic group, but that isn’t the type of distinction usually made in these kinds of studies.)
wouldbecouldbe 3y ago
Yeah and as well as soldiers being exposed to different chemicals & other circumstances then the general population. Would be great if they would compare it with other army base around the same time.
- alistairSH 3y ago
  They did... the control was Camp Pendleton.
q1w2 3y ago
The problem with this study is even more profound. They only looked at two military bases. One with high TCE, and one with low TCE. ...but there could be thousands of causal differences between two locations. They should have looked at dozens of military bases across the country/world.
- jameshart 3y ago
  Why? This wasn’t a fishing expedition where they took two cohorts of marines and looked down a list of 20 diseases to find one with p<0.05 distribution between the two cohorts. > Occupational exposure to the industrial solvent trichloroethylene (TCE) was previously associated with a 6-fold increased risk of Parkinson disease (PD) in a small study of twin pairs discordant for PD.1 Animal studies provide biological plausibility for this association by recapitulating key pathologic characteristics of PD Given this - a previous finding, a plausible mechanism - they went and found two good existing cohorts who had different exposure to the compound of interest and for whom they could access medical records. That is good study design. Which is probably why it got published.
jameshart 3y ago
Scientists have heard that correlation is not causation too. From the paper (https://jamanetwork.com/journals/jamaneurology/fullarticle/2805037 https://jamanetwork.com/journals/jamaneurology/fullarticle/2...): > To control for potential confounding, we included age, sex, race (Black, White, other), and ethnicity (Hispanic, non-Hispanic) in all models. We also tested models that included rank (officer, enlisted) and smoking status (ever, never), though smoking status was unknown for a substantial proportion of the cohort. We repeated analyses in subgroups defined by sex and by race and ethnicity. We conducted several analyses to explore possible biased ascertainment of PD in Camp Lejeune veterans due to potential awareness of the contamination and presumptive service connection that entitles them to VA benefits. … > We additionally tested associations in men and women separately and conducted sensitivity analyses that adjusted for total number of years of VHA health care usage. These analyses were evidently deemed adequate by peer reviewers. If anyone thinks there are other confounding factors they can go ahead and do that analysis and publish as well. Sciencing continues.

calvinmorrison 3y ago

Presumably there's already known risk factors studied thoroughly for race, age, and sex. So they adjusted the numbers to account for that and their focus was on locality.

AdamN 3y ago

Alot of socioeconomic factors are baked into the above co-morbidities but anyway, is there a reason to think that veterans of two different marine camps have significantly different socioeconomic profiles from eachother?

notakio 3y ago
In this case (Lejeune vs Pendleton), there would likely not be a substantial socioeconomic difference between the collective backgrounds of Marines who did basic training at either one. But comparing either camp to OCS at Quantico would, in fact, show a pretty stark delineation between the socioeconomic backgrounds.
- alistairSH 3y ago
  They looked at officer vs enlisted, which would cover any socioeconomic difference between basic vs OCS, no?
- pmoriarty 3y ago
  There might not have been much difference between them at the time, but who knows how their lives went after their time there? Some might have wound up being relatively wealthy compared to the rest, and that could have influenced their long-term health. We won't know until we check.

hgsgm 3y ago

What happens when you end up accidentally controlling for exposure to the chemical?

bumby 3y ago

They were all active duty military and largely the same socio-economic cohort, and use the same medical system. Maybe they could draw a distinction between enlisted and commissioned, but my hunch is the disparity between raw numbers would lead to low statistical power. (This isn’t to say they originally came from the same socio-economic group, but that isn’t the type of distinction usually made in these kinds of studies.)

wouldbecouldbe 3y ago

Yeah and as well as soldiers being exposed to different chemicals & other circumstances then the general population. Would be great if they would compare it with other army base around the same time.

alistairSH 3y ago
They did... the control was Camp Pendleton.

q1w2 3y ago

The problem with this study is even more profound. They only looked at two military bases. One with high TCE, and one with low TCE. ...but there could be thousands of causal differences between two locations. They should have looked at dozens of military bases across the country/world.

jameshart 3y ago
Why? This wasn’t a fishing expedition where they took two cohorts of marines and looked down a list of 20 diseases to find one with p<0.05 distribution between the two cohorts. > Occupational exposure to the industrial solvent trichloroethylene (TCE) was previously associated with a 6-fold increased risk of Parkinson disease (PD) in a small study of twin pairs discordant for PD.1 Animal studies provide biological plausibility for this association by recapitulating key pathologic characteristics of PD Given this - a previous finding, a plausible mechanism - they went and found two good existing cohorts who had different exposure to the compound of interest and for whom they could access medical records. That is good study design. Which is probably why it got published.

jameshart 3y ago

Scientists have heard that correlation is not causation too. From the paper (https://jamanetwork.com/journals/jamaneurology/fullarticle/2805037 https://jamanetwork.com/journals/jamaneurology/fullarticle/2...): > To control for potential confounding, we included age, sex, race (Black, White, other), and ethnicity (Hispanic, non-Hispanic) in all models. We also tested models that included rank (officer, enlisted) and smoking status (ever, never), though smoking status was unknown for a substantial proportion of the cohort. We repeated analyses in subgroups defined by sex and by race and ethnicity. We conducted several analyses to explore possible biased ascertainment of PD in Camp Lejeune veterans due to potential awareness of the contamination and presumptive service connection that entitles them to VA benefits. … > We additionally tested associations in men and women separately and conducted sensitivity analyses that adjusted for total number of years of VHA health care usage. These analyses were evidently deemed adequate by peer reviewers. If anyone thinks there are other confounding factors they can go ahead and do that analysis and publish as well. Sciencing continues.