Cancer, Stroke and Diabetes in USA - Environment versus Genetics

Cancer, stroke and diabetes are the three major causes of death in USA, and as a result, the government spends humongous amount of research money to figure out the root causes of those diseases. Our readers left many thoughtful comments on the relevance of #GWAS, and suggested that maybe environmental factors affect 10% of the cases, and but we still need to know the genetic contribution. Will the same argument be true, if environment causes 50% of cancers? What if the contribution is close to 90%? Of course, we do not have any estimate for the environmental component, but the following charts appear very suggestive.

Cancer

Let us first take a look at the cancer mortality distribution. We see many red dots (high mortality rate) concentrated at one part of the country. It is quite possible that those people have bad cancer gene.

Diabetes

We also got county-wide distribution of diabetes around the country from CDC. Strange, the same group of people have bad diabetes genes as well.

Stroke

We got the stroke statistics from strokecenter.org. Bad heart genes seem to be concentrated around the same part of the country - Arkansas, Alabama, Lousiana, Georgia, Oklahoma, Mississippi, etc.

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**Demographics - What is the genetic make-up of those in cancer, stroke and diabetes prone areas? **

Let us look at who lives in those areas. The following chart shows the county- wide demographic distribution of USA from 2000 census. Clicking on the figure will take you to main wiki page with a much larger figure. First thing you will notice is that USA is highly segregated. We will not go into the details of every region and rather focus on the disease-prone areas to see the genetic make-up of people.

The first group we find there are those marked in ‘purple’. They are the American blacks from southern states. Does our disease-data suggest that the blacks have all kinds of bad genes? Not really, because the yellow region right above purple also falls within the disease-prone parts of the country. What is the genetic make-up of those living in yellow region? Although the map says ‘American’, in terms of genetic origin, they are mostly Scotch-Irish (Scots Irish) or immigrants from Ulster-region. Here is the history.

Upon arrival in America, the Scotch-Irish at first usually referred to themselves simply as Irish, without the qualifier Scotch. It was not until a century later, following the surge in Irish immigration after the Great Irish Famine of the 1840s, that the descendants of the earlier arrivals began to commonly call themselves Scotch-Irish to distinguish them from the newer, largely destitute and predominantly Roman Catholic immigrants.[11] The two groups had little interaction in America, as the Scotch-Irish had become settled years earlier primarily in the Appalachian region, while the new wave of Irish American families settled primarily in northern and midwestern port cities such as Boston, New York, or Chicago. However, many Irish migrated to the interior in the 19th century to work on large-scale infrastructure projects such as canals and railroads.[12]

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Most Scotch-Irish headed for Pennsylvania, with its good lands, moderate climate, and liberal laws.[citation needed] By 1750, the Scotch-Irish were about a fourth of the population, rising to about a third by the 1770s.[citation needed] Without much cash, they moved to free lands on the frontier, becoming the typical western “squatters”, the frontier guard of the colony, and what the historian Frederick Jackson Turner described as “the cutting-edge of the frontier.”[39]

The Scotch-Irish moved up the Delaware River to Bucks County, and then up the Susquehanna and Cumberland valleys, finding flat lands along the rivers and creeks to set up their log cabins, their grist mills, and their Presbyterian churches.[citation needed] Chester, Lancaster, and Dauphin counties became their strongholds, and they built towns such as Chambersburg, Gettysburg, Carlisle, and York; the next generation moved into western Pennsylvania.[40] With large numbers of children who needed their own inexpensive farms, the Scotch-Irish avoided areas already settled by Germans and Quakers and moved south, down the Shenandoah Valley, and through the Blue Ridge Mountains into Virginia.[citation needed] These migrants followed the Great Wagon Road from Lancaster, through Gettysburg, and down through Staunton, Virginia, to Big Lick (now Roanoke), Virginia. Here the pathway split, with the Wilderness Road taking settlers west into Tennessee and Kentucky, while the main road continued south into the Carolinas.[41][42]

So, if we like to explain prevalence of cancer, stroke and diabetes in terms of genes, we will find that two groups - southern blacks and southern Scots- Irish immigrants have the worst forms of genes.

But what if genes have nothing to do with prevalence of cancer, stroke and diabetes in those regions? What if the following chart (showing hunger) and other fifty similar charts showing poverty distribution is a better explanation?

If the largest presence of cancer, stroke and diabetes in USA can indeed be explained by poverty, which is an environmental factor, why are we spending any money chasing genes?