. Author manuscript; available in PMC: 2016 Sep 17.

Published in final edited form as: Eur Spine J. 2016 Jun 6;25(9):2716–2720. doi: 10.1007/s00586-016-4612-3

Table 1.

Comparison of twin cases and controls

	T2D cases	Controls	Total	p value
N	63 (6.6 %)	893 (93.4 %)	956
Females	61 (6.4 %)	856 (89.5 %)	917 (95.9 %)	0.71
Age (SD) years	59.4 (7.3)	53.6 (8.3)	53.9 (8.4)	<0.001
BMI (SD) kg/m²	27.3 (5.2)	24.6 (4.1)	24.7 (4.3)	<0.001
Smoking
Non	31 (3.2 %)	422 (44.1 %)	453 (47.4 %)
Ex	21 (2.2 %)	246 (25.7 %)	267 (27.9 %)	0.49
Current	7 (0.7 %)	124 (13.0 %)	133 (13.7 %)
Alcohol	2.4 (SD = 1.2)	2.8 (SD = 1.4)	2.8 (SD = 1.4)	0.03
Zygosity
MZ	28 (2.9 %)	290 (30.3 %)	318 (33.3 %)	0.05
DZ	35 (3.7 %)	603 (63.1 %)	638 (66.7 %)
LDD score	14.9 (SD = 6.5)	13.1 (SD = 7.7)	13.2 (SD = 7.7)	0.04

The LDD score is the summation of four features (disc height, disc signal intensity, disc bulge and anterior osteophytes) each coded 0–3, summed over the five lumbar discs. Alcohol consumption was by self-report, averaged over one week in a lifetime, in alcohol units