Table 1

Observed numbers (Obs) patients in the cohorts of people with AVM, SAH, stroke, and transient ischaemic attack, who had a subsequent hospital diagnosis of ALS; expected numbers (Exp) based on comparison with the reference cohort; rate ratios and 95% CI

‘Exposure’ diseaseObsExpRR95% CIp Value
All AVM (n=12 220)†93.32.691.23 to 5.120.005*
AVM, cerebral vessels (n=6345)51.72.891.20 to 6.940.035*
AVM, pre-cerebral vessels (n=872)10.33.950.10 to 22.040.623
AVM, peripheral (n=6640)41.72.390.65 to 6.130.158
All stroke (n=1 004 289)†598450.81.381.27 to 1.51<0.001*
Haemorrhagic (n=179 717)8464.81.31.04 to 1.620.019*
Ischaemic (n=526 575)306238.21.311.16 to 1.47<0.001*
Unspecified (n=389 919)269178.21.551.36 to 1.75<0.001*
SAH (n=59 227)2819.11.470.98 to 2.130.053
Transient ischaemic attack (n=265 676)243168.41.471.29 to 1.68<0.001*
  • *p<0.05.

  • †Total exceeds constituent groups because the same patient may have a different diagnosis at different admissions. In this circumstance, the researchers have no way of knowing which diagnosis is the most appropriate one. The rate ratio is calculated from the formula (O/E) in the exposure cohort divided by (O/E) in the reference cohort. O/E, Observed numbers/expected numbers.

  • ALS, amyotrophic lateral sclerosis; AVM, arteriovenous malformation; SAH, subarachnoid haemorrhage