Association of smoking with amyotrophic lateral sclerosis risk and survival in men and women: a prospective study

BMC Neurology

Table 1 Characteristics of amyotrophic lateral sclerosis (ALS) cases and controls, General Practice Research Database, 1990-2008

	ALS cases	Controls
N	1143	11,371
Age at index date, years	67.4 (12.5)	67.1 (12.5)
Range	23-95	20-97
Gender [% women]	44.8	44.9
Smoking [%]
Never	33.0	32.7
Missing	16.7	18.0
Ever	50.3	49.4
Former	23.9	23.7
Current	26.4	25.7
Non-heavy smokers	45.1	44.5
Heavy smokers	5.2	4.9
Body mass index, kg/m² [%] *
<20	3.6	3.2
20-24.9	33.1	30.1
25-29.9	29.5	30.7
≥30	9.5	11.9
Missing	24.3	24.2
Time between first smoking assessment and index date, years	14.1 (9.4)	14.0 (9.2)
Diagnosis [%]
ALS/MND	88.6
PBP	8.8
PMA	1.4
PLS	1.2
Follow-up after diagnosis, years	2.1 (2.7)

Numbers refer to percentages or means (standard deviation).
* Corresponding to first recording of body mass index in the GPRD (average 8.3 years before index date)
ALS: amyotrophic lateral sclerosis; MND: motor neuron disease; PBP: progressive bulbar palsy; PLS: primary lateral sclerosis; PMA: progressive muscular atrophy

ISSN: 1471-2377