Use of Satscan to Detect Spatial Clusters in Five Regions of Britain

Epi-on-the-IslandTime Series Regression (TSR)6-10 July 2015

Wed 1: DLNMs Ben ArmstrongLondon School of Hygiene and Tropical Medicine1

The trailer

DLNMs~200 papers 2011-

At least one in vet epi:

Morignat 2015 Env Res

Easy R package!

The algebra terminology:- Recall general model form[In this example, temperature is the variable of interest.]3Distributed lag non-linear models (DLNMs)The shape story (Nonlinear Ms, eg splines)

The lag story (DLMs)

The lag-shape story (DLNMs)

Autocorrelation not very important outside infectious diseases4

The shape story: non-linear options:Cold effectHeat effectThresholds

5Other non-linear options

6Net RR increment (%)over 28 days per degree above 20 (95% CI):

5.0(3.7,6.3)

4.9(3.6,6.2)

4.9(3.7,6.2)

Recall: distributed lag models (DLM)

The lag story:

7The lag-shape story8The lag-shape problem:

Seek combined virtues of:

Smooth temp-mort curves

Smooth effects of lag.

Solution: assume DLMs for each coefficient of a basis variable .e.g.: RR by temperature (NCS) and lag(NCS)

Heat effects:Different slope for each lag

DLNM: simple(r) caseUse a linear threshold modelFit a distributed lag model (DLM) to the heat slope11DLMs taken from econometricsSimple(r) to general DLNM:

Shape flexibility

+

Lag flexibility

=

Total flexibiltyArmstrong 2006Basis variablesExtend this to any set of basis variables (eg splines)Armstrong 2006

Gasparrini 2010

DLNM R code example (London data)# MAKE DLNM BASIS VARIABLEbasis.temp