A Medical Mystery of the Best Kind: Major Diseases Are in Decline

[magila]

On the other hand, autoimmune diseases have been increasing in prevalence over the last century. While these diseases are rarely immediately fatal, in severe cases they can have a major impact on quality of life. Onset often occurs in early adulthood so the cost of treatment over a lifetime can be extremely high. The usual treatment, immunosuppressive therapy, also has serious risks of its own.

While there has been much progress on finding new treatments, their scope has been limited to new and creative ways of suppressing the immune system. There are a multitude of theories which attempt to explain the causes of autoimmune diseases, but we seem to be quite far from truly understanding them.

[mrfusion]

I always wondered if the removal of lead in gasoline could account for a lot of this. Especially the dementia drop.

[SCAQTony]

It is never one thing; your lead assessment is probably a serious contender among other pollutants. Then there is better hygiene via food handlers, stiffer USDA rules, cleaner water, less smoking and second hand smoke, more people exercising too.

[ChuckMcM]

There have been a number of meta studies which have tried to link the removal of lead from gasoline and the drop in violent crime. The correlate well.

[lordnacho]

Speculation:

- People have become more aware of the risk factors, and behave accordingly. Awareness would be connected to prevalence but have a lagged effect.

- Deadly diseases cause evolutionary responses. Perhaps a disproportionate number of people with predisposition to these illnesses passed away before having offspring.

- Reporting bias? While an illness looms large in the minds of the medical community, doctors are more likely to either wrongly attribute to the illness (false positive), or do false negatives less often.

- Highly speculative: combined effects are non-linear. I don't know what they use to do these studies, but typically you hear something along the lines of "for every x, there's m*x effect", which makes things sounds nice and linear. Maybe better prevention and better treatment does better than either on its own summed up, and so you won't be able to find the "reason" by splitting into each feature.

[tlrobinson]

I don't think you'd see any significant evolutionary responses in the timeframes the article is talking about (<100 years or 4 generations)

[FreeKill]

Yeah, I was curious about that as well. I wonder if the internet and the resulting increase in spread of knowledge about diseases, symptoms, etc. has played a statistically significant part? I'd wager that at the least, it has helped people to realise they need more of an experts opinion when certain symptoms arrive that are linked to more serious illnesses.

[tenpies]

> People have become more aware of the risk factors, and behave accordingly.

I wonder how this could be properly measured. My impression based on rising obesity rates and decrease in overall physical activity levels is that we are terrible at making sacrifices in the present for our future self.

Sure, we all avoid trans-fats, leaded fuel, and other similar choices; but all of these are largely forced on the entire population.

[sgt101]

wow - I have no clue (obviously) but possible reasons :

- better home heating (less open fires, more heated bedrooms)

- increased time from atmospheric nuclear bomb testing (and the various dispersals of plutonium in the 60's and 70's)

- better nutrition in general

- higher genetic diversity in breeding populations; not many peoples grandparents all come from the same village in the developed world now

- less pollution in the west; import of finished goods rather than local manufacturing

[ekianjo]

> increased time from atmospheric nuclear bomb testing (and the various dispersals of plutonium in the 60's and 70's)

Ambient radioactivity, under a certain threshold (which is disputed) has actually shown some positive effects. If I remember correctly, folks living in naturally more radioactive areas have been showing lower cancer rates vs the average.

[codecamper]

You beat me to it. My guess would be increased time from those atmospheric nuke tests.

Those were crazy days! The Tsar Bomba. What was the world thinking?

[kiba]

We might actually benefit from some amount of radiation, rather than assuming that increased amount of radiation equals higher cancer risk.

It's called radiation hormesis. Though I don't think there's a scientific consensus on this issue.

[ktRolster]

This is weird:

  >Until the late 1930s, stomach cancer was 
  >the No. 1 cause of cancer deaths in the 
  >United States.

[bane]

In countries which still practice wide-scale pickling, curing and fermentation -- stomach cancer rates are still very high.

http://www.reuters.com/article/us-salty-diet-idUSTRE62N4KX20...

While gastric cancer is declining, it is still the most common cancer in Korea. Past studies have yielded conflicting results as to whether a salty diet causes gastric cancer, though most found an association between salt use and gastric cancer.

Here's another piece of information: https://en.wikipedia.org/wiki/Refrigerator

The introduction of Freon in the 1920s expanded the refrigerator market during the 1930s. Home freezers as separate compartments (larger than necessary just for ice cubes) were introduced in 1940.

[_mhr_]

I found a chart showing the prevalence of multiple forms of cancer over time: http://i52.tinypic.com/r9euci.jpg.

[sjg007]

Widespread refrigeration removed the need for cured and salted meats. This is widely thought to explain the discrepancy.

[mc32]

Does that take into account refrigeration? Maybe it's totally unrelated --but prior to refrigeration a lot of meats were cured.

[autokad]

stomach cancer was spiked due to h-pylori. water treatments put a huge dent in that

[transcranial]

Currently, South Korea and Japan have the highest incidences of stomach cancer. It's typically attributed to cured foods and processed meats. Prior to refrigeration, wide consumption of these foods were out of necessity.

[RA_Fisher]

I bet it's related to smoked fish and other smoked food products.

[sjclemmy]

What about widespread use of painkillers? Aspirin, paracetamol and ibuprofen have become common place over this period. Calming the body's immune response might have a beneficial effect on overall health.

[autokad]

cancer is caused by swelling, thus anything that reduces it will reduce cancer incidents.

[codecamper]

I wonder if all the benefits may be coming from people having kids later in life. You'd think this would lead to more disease, but maybe we are actually evolving to be longer living and the kids later in life is what is causing it.

[mrfusion]

It mentions statins as something obviously good but is there any evidence they're actually beneficial? I thought cholesterol was good now?

[carbocation]

LDL cholesterol and triglycerides are harmful. Higher values of those cause higher risk of coronary artery disease and earlier death. HDL cholesterol ("good cholesterol") appears to have no effect, at least the scalar quantity that we measure with current lab tests.

Statins reduce risk of death in proportion to their reduction of LDL cholesterol, so most likely this effect is a consequence of decreased LDL cholesterol.

[rollthehard6]

Some doctors and researchers believe the benefit from statins is more to do with the decrease in inflammation caused by them. Possibly widespread use of statins has beneficial effects on other disease processes too.

[no_flags]

LDL is still "bad" and HDL is still "good", but that means in your blood, not your diet. The evidence linking dietary cholesterol and saturated fat to cardiovascular disease is weak.

Dr. Peter Attia provides an excellent summary of the topic here: https://www.youtube.com/watch?v=nhzV-J1h0do

[sukilot]

Citation?

[raverbashing]

The question I guess is not what diseases are in decline, but which ones are going up

[transcranial]

Apparently Parkinson's disease has been on the rise over the past several disease, some say due to the decrease in smoking. Which is fascinating, as smoking has been shown to be actually protective against Parkinson's.

[Gibbon1]

Ans: Diabetes

[gedy]

"Going up" usually just means in percentage, as more serious diseases decline below that percentage.

[robbles]

Is it possible that medical advances in the last couple of decades have simply delayed the deaths of many sufferers? Heart disease and cancer survival rates are usually qualified with a number of years, given that they are difficult to fully cure. With a larger aging population just barely hanging on, perhaps an upswing is just around the corner but hard to see now. i.e. the rate of death has not actually dropped, the average survival time is longer.

[lastres0rt]

Put bluntly: All of these 'little increases" are starting to add up in big ways. I'm not that surprised that a decline in one disease is leading to declines in others. As we all live a little longer, we make each other healthier as well, being better able to cope with the expanded safety net.

As someone who's seen her grandparents suffer with a cacophony of diseases right before death? Sometimes, one thing really DOES lead to another.

[throwwit]

The largest extrinsic factor (causally effective), should be the environment's physiological interaction with cells that have accumulative exposure: the alimentary system. Lower incidences of alimentary cancers should be the hallmark result of bans on various carcinogenic additives. The question should be how low the rates can inherently go based on diet alone, and to then proceed to narrow down the scope of any further factors.

[known]

Check https://en.m.wikipedia.org/wiki/WHO_Model_List_of_Essential_... and https://en.m.wikipedia.org/wiki/List_of_bestselling_drugs

[JoeAltmaier]

Is it simply, that fewer people can afford insurance/visit a doctor? So they die of 'natural causes' and never get diagnosed?

[nxzero]

Curious, if the cause is the decline in cigarette consumption; here's a graph showing roughly 100 years of data for the topic:

http://4.bp.blogspot.com/-p4ECPyex_cY/TzSalazW2XI/AAAAAAAAA2...

[jschwartzi]

The lines do seem to correlate. In the case of stomach cancer, I'm wondering if there's a similar correlation between the decline in chewing tobacco and the decline in stomach cancer. Chew is full of fiberglass and other stuff, and if you swallow any of the juice you're swallowing that stuff. It's impossible to clear it all from your mouth after you finish chewing, too.

[alphaoverlord]

One explanation can be expanding criteria and/or earlier diagnosis. Earlier diagnosis, even with the same treatment efficacy, will lead to records of improved survival, and expanding criteria of particular diagnoses will often identify borderline cases that likely don't have the same morbidity and mortality.

[triadicmonad]

Of course hundreds of probable individual causes can be attributed to this phenomenon. The Galileo of medicine will be the one who can unify and make the data sensible without pretending one or two factors caused it all.

[dmix]

Better home food (popularity of brown bread vs white bread), better take out food (not just McDonald's and diners anymore), and more indoor working conditions (less exposure to pollution) likely play a big part.

[artagnon]

Our genes are somehow improving in quality (survival longevity, quality of life, IQ), and this effect is cascading over generations. I don't know if it can be explained using pure epigenetics, and natural evolution is certainly too slow to explain this, so there might be mutagens in our everyday environment that directly modify the DNA sequence. We recognize cigarette smoke, heavy metals as mutagens, but are there more subtle mutagens that lead to better DNA?