Table 1. Characteristics of patients in the endometriosis group and the control group, 2002–2013.

	EMS group	Control group	Total	p-value
Number of patients	997	3,988	4,985
2009 a	183
2010 a	198
2011 a	198
2012 a	201
2013 a	217
Mean age group b	8.5±1.8	8.5±1.9	8.5±1.8	1
Mean age (years) c	42.6±9.2	42.6±9.3	42.6±9.3
Mean group socioeconomic status d	6.0±2.9	6.0±2.9	6.0±2.9	1
Nickel allergy				0.052 e
Present	8 (0.8%)	13 (0.3%)	21
Not present	989 (99.2%)	3975 (99.7%)	4964

^a First diagnosis of EMS was made in the year noted.

^b Mean age groups per 5 years in 2013. 1; 0–4 years, 2; 5–9 years,……., 17; 80–84 years, 18; 85 years+.

^c The mean age was calculated from the mean age groups per 5 years.

^d Mean socioeconomic status groups in 2013. 1; upper 0–9%, 2; upper 10–14%,……., 9; upper 90–94%, 10; upper 95%+.

^e Fisher’s exact test

Data are presented as numbers or means ± standard deviations