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Table 1 Lag analysis: change in incidence rates/100,000 population for Ambulance and ED convulsions in children < 6 years associated with a 1/100,000 population increase in all ages ED influenza-like illness and bronchiolitis in children < 3 years

From: Relationship between the population incidence of febrile convulsions in young children in Sydney, Australia and seasonal epidemics of influenza and respiratory syncytial virus, 2003-2010: a time series analysis

Independent Variable

Lag1 (weeks)

Ambulance Convulsions

ED Convulsions

  

Parameter estimate

(95% CI)

P-value

Parameter estimate

(95% CI)

P-value

 

-2

2.907 (2.374-3.440)

<0.0001

5.119 (4.535-5.704)

<0.0001

ED2

-1

3.240 (2.769-3.711)

<0.0001

6.678 (6.181-7.175)

<0.0001

Influenza-

0

2.948 (2.483-3.412)

<0.0001

6.597 (6.096-7.099)

<0.0001

like illness

+1

0.122 (-0.065-0.309)

0.203

0.546 (0.247-0.844)

0.0004

 

+2

-0.013 (-0.143-0.118)

0.8483

0.083 (-0.132-0.298)

0.4499

 

-2

-0.007 (-0.014-0.000)

0.0631

-0.008 (-0.016--0.001)

0.033

ED3

-1

0.005 (-0.002-0.012)

0.1559

0.023 (0.015-0.030)

<0.0001

Bronchiolitis

0

0.002 (-0.005-0.009)

0.5969

0.020 (0.013-0.028)

<0.0001

 

+1

0.002 (-0.005-0.008)

0.6648

-0.006 (-0.014-0.002)

0.1187

 

+2

0.011 (0.004-0.018)

0.0017

-0.010 (-0.017--0.002)

0.013

  1. 1A negative lag refers to a change in convulsions incidence occurring prior to the change in ILI or bronchiolitis ED visits. A positive lag indicates convulsions incidence changes after the change in ILI or bronchiolitis.
  2. 2To control for trend and seasonality, a natural cubic spline with 4 degrees of freedom per year was used.
  3. 3To control for trend and seasonality, a natural cubic spline with 4 degrees of freedom per year was insufficient, so 8 degrees of freedom were used.