Table 1.

Demographic information.

	Chronic pain	Control
	Total (Male, Female)	Total (Male, Female)
Total number of participants	38 (16, 22)	38 (16, 22)
	Mean (standard deviation)	Mean (standard deviation)
Age (years)	45.6 (9.9)	44.2 (10.4)
Duration since last consumption of:
Nicotine (h)	1.6 (3.5)	3.1 (6.6)
Caffeine (h)	5.3 (10.7)	5.8 (8.3)
Years of Education	13.8 (3.8)	15.2 (3.0)
	Total aged ≥ 45 years/<45 years	Total aged ≥ 45 years/<45 years
Number of participants in each age classification	22/16	17/21
	Percentage of participants in group	Percentage of participants in group
% of participants who smoke	50.0	18.4**

^**p < 0.01.