Association of the practice of contact sports with the development of amyotrophic lateral sclerosis

Figures & data

Figure 1 (A) Age of contact sports practitioners by gender (controls vs patients); (B) Age of non-practitioners of contact sports by gender (patients vs controls).

Figure 2 Tobacco exposure for male study participants. Tobacco exposure was higher for the practitioners of contact sports, especially in patients compared to controls. Note that this difference is not observed in those participants that did not practice contact sports. (Several outliers with TE up to 175 “packs per day” times “years smoked” are not shown.)

Table 1 Demographic and clinical characteristics of the participants.^a

	Total (n = 2247)			Male (n = 1198)			Female (n = 1049)
	Patients (n = 1326)	Controls (n = 921)	p-Value**	Patients (n = 768)	Controls (n = 430)	p-Value**	Patients (n = 558)	Controls (n = 491)	p-Value**
Age (mean ± sd)	61.9 ± 12.9	56.0 ± 15.1	<0.001	60.7 ± 12.8	57.0 ± 15	<0.001	63.5 ± 12.8	55.1 ± 15.2	<0.001
Smoking (n, %)			0.006			0.68			<0.001
Never	738 (56.3%)	536 (58.3%)		342 (45.2%)	197 (45.9%)		396 (71.5%)	339 (69.2%)
Ex-smoker	402 (30.7%)	232 (25.2%)		287 (37.9%)	153 (35.7%)		115 (20.6%)	79 (16.1%)
Current	171 (13%)	151 (16.4%)		128 (16.9%)	79 (18.4%)		43 (7.8%)	72 (14.7%)
Tobacco exposure (mean ± sd)	10.4 ± 20.2	8.6 ± 17.2	0.036	14.1 ± 22.4	12.4 ± 20.1	0.213	5.8 ± 15.8	5.5 ± 13.6	0.79
Practice contact sport (n, %)	152 (11.6%)	69 (7.5%)	0.002	145 (19.2%)	51 (11.9%)	0.001	7 (1.3%)	18 (3.7%)	0.02
Age at 1st manifestation (mean ± sd)	59.4 ± 13.4	–	–	58.1 ± 13.3	–	–	61.3 ± 13.4	–	–
Age at diagnosis (mean ± sd)	60.9 ± 13.2	–	–	59.6 ± 13.1	–	–	62.6 ± 12.8	–	–
ALSFRS-R decay (mean ± sd)	0.82 ± 1	–	–	0.77 ± 1	–	–	0.91 ± 1.1	–	–
Onset (n, %) bulbar/limbs	335 (26.6%)/ 925 (73.4%)	–	–	145 (19.9%)/585 (80.1%)	–	–	190 (35.8%)/350 (64.2%)	–	–

^aSome percentages are calculated on denominators smaller than the table heading, due to missing values in some variables. **p-Value for comparisons between patients and controls.

Bold values signify p= 0.05.

Figure 3 Years of practice of contact sports (black – controls; grey – patients) There is no significant difference in the duration of this practice (p = 0.24). (Of the 221 participants who practiced contact sports, this information was available for 190, and the y-axis is just an index for participant.).

Table 2 Results of univariate logistic models for the outcome ALS.

Variable	OR	95% CI	p-Value
Contact sport (Yes)	1.76	[1.26; 2.51]	0.001
Age (per year)	1.03	[1.02; 1.04]	<0.001
Smoking (No)	Ref.
Ex-smoker	1.26	[1.04; 1.53]	0.022
Yes	0.82	[0.64; 1.05]	0.119
Tobacco exposure^a	1.005	[1.001; 1.01]	0.038

^aDefined as “packs smoked per day” times “years smoked.”

Table 3 Final multivariate logistic model for outcome ALS.

	OR	95% CI	p-Value
Intercept	0.6	[0.34; 1.07]	0.08
Contact sport (Yes)	1.35	[0.88; 2.12]	0.19
Age (per year)	1.02	[1.01; 1.03]	<0.001
Tobacco exposure	0.999	[0.99; 1.01]	0.7
Contact sport (Yes) × Tobacco exposure^a	1.03	[1.004; 1.05]	0.03

^aDefined as “packs smoked per day” times “years smoked.”

Data availability statement

The data that support the findings of this study are available from the authors, upon reasonable request.