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Classification of common human diseases derived from shared genetic and environmental determinants

Kanix Wang, Hallie Gaitsch, Hoifung Poon, Nancy J Cox, Andrey Rzhetsky. Classification of common human diseases derived from shared genetic and environmental determinants. Nature Genetics 49, 2017.

tl;dr

  • Look at genetic and environmental correlations between disesases to construct etiological disease taxonomy.
  • Takeaway 2
  • Open question or critique

Contributions

What is this paper showing? What are the contributions? What kind of paper is it: theoretical, applied, something in the middle? Where does it fit into the prior body of work?

Data

The paper uses insurance claims from Truven MarketScan, which contains information from roughly one third of the US population.

  • Of available data, only used 129k due to inclusion criteria
  • Focuses on parents and children that were both "visible" for at least 6 years

Heritability

  • The more heritable, the less prevalent a disease is.
  • Of 65 diseases that had previously published heritability estimates, 52 agreed with estimates within 95% CI interval.
  • Verify common wisdom that early onset has higher heritability w/ correlation, and showed no correlation across all diases but showed links within smaller categories

Genetic and environmental correlations

  • Focused on 29 diseases which are well represented in parents and children in data. Applied pairwise correlation assuming a 1% false discovery rate.
  • Genetic correlations stronger than environmental correlations. For neuropsychiatric disease pairs, genetic and environmental correlations were equal.
  • Confidence intervals for family-based estimates were much narrower than an earlier genome-wise association study, due to the large sample size of the dataset.
  • Some common diseases (asthma, rhinitis, dermatitis) were surprisingly correlative genetically.
  • Used ICD-9 taxonomy to compared against genetic and environmental correlations. Migranes is considered a digestive illness?

Nosologies

  • Defining distance as 1 - correlation, we can sample distances from the posterior distribution of a disease. I'm assuming classification is nearest neighbors based on distances as probabilities.

Discussion

  • Considerations for bias: urban, more affluent, assortive mating, lack of ethnicity and race information.

Methodology (updated)

  • Starts with linear model of y = X\beta + a + c + s + f + e
  • Variance of y can be decomposed into different factors

Extensions

  • David's student took BCBS data and did a similar study about genetic and environment. Had race data
  • Probability of getting disease if your parent had it?
  • Diseases diagnosed after age of 30 would be missed.

Questions

  • What are GCS and GC models? What methods in addition to straight correlation are done? Could be done?
  • What does unique environment vs common-couple mean? Common couple probably means a couple that has a child, but what about unique environment?
  • What kind of enviornmental data did they have?
  • Why these spiral visualizations? Hard to compare y-values but does give long x-axis for bar chart.
  • Still confused about classification by sampling stuff?