Table 3. Within-Pair Percent Difference in Heart Rate Variability per 1-Unit Within-pair Difference in the Mediterranean Diet Score, Overall and by Zygosity^*.

	MZ+DZ		MZ		DZ		Interaction withZygosity P value
	Within-pair Difference (%) (95% CI)	P value	Within-pair Difference (%) (95% CI)	P value	Within-pair Difference (%) (95% CI)	P value
Time domain
Model 1: Zygosity and nutritional factors not in the score adjusted†
SDNN, ms	2.2 (0.2, 4.2)	0.03	1.7 (−0.7, 4.2)	0.16	2.8 (−1.0, 6.9)	0.15	0.63
SDANN, ms	2.0 (−0.2, 4.2)	0.07	1.7 (−1.0, 4.4)	0.21	1.8 (−2.4, 6.1)	0.40	0.93
SDNNI, ms	3.9 (1.7, 6.0)	0.001	2.8 (0.3, 5.3)	0.03	7.6 (3.3, 12.0)	0.001	0.09
rMSSD, ms	4.2 (1.0, 7.5)	0.01	2.8 (−1.1, 7.0)	0.15	5.4 (−0.2, 11.3)	0.06	0.43
pNN50, %	12.9 (4.0, 22.5)	0.004	7.1 (−3.4, 19.0)	0.19	22.0 (6.5, 39.9)	0.005	0.13
Model 2: Multivariate adjusted‡
SDNN, ms	1.9 (−0.1, 3.9)	0.07	1.3 (−1.1, 3.7)	0.28	1.2 (−2.4, 4.9)	0.51	0.80
SDANN, ms	1.8 (−0.4, 4.0)	0.11	1.3 (−1.3, 3.9)	0.33	0.5 (−3.2, 4.4)	0.79	0.95
SDNNI, ms	3.5 (1.3, 5.6)	0.002	2.3 (−0.3, 4.9)	0.08	5.2 (1.4, 9.2)	0.009	0.17
rMSSD, ms	3.5 (0.2, 6.8)	0.04	1.9 (−2.0, 5.9)	0.34	1.8 (−4.2, 8.3)	0.54	0.47
pNN50, %	11.1 (2.4, 20.4)	0.01	4.8 (−5.4, 16.3)	0.36	11.9 (−2.6, 28.4)	0.11	0.20
Frequency domain
Model 1: Zygosity and nutritional factors not in the score adjusted†
TotPow, ms2	4.9 (0.9, 9.2)	0.02	4.1 (−0.3, 9.2)	0.07	6.2 (−2.6, 15.1)	0.17	0.80
ULF, ms2	4.0 (−0.5, 8.7)	0.08	3.0(-2.1, 8.8)	0.24	4.1 (−5.0, 14.0)	0.38	0.88
VLF, ms2	7.1 (2.4, 12.0)	0.003	6.2 (0.2, 11.4)	0.04	12.7 (4.3, 22.6)	0.004	0.26
LF, ms2	13.0 (6.3, 20.0)	<0.0001	9.4 (1.2, 17.2)	0.023	25.9 (12.7, 39.1)	<0.0001	0.052
HF, ms2	7.4 (0.1, 15.1)	0.047	3.0 (−5.7, 13.2)	0.48	12.7 (0.4, 26.2)	0.042	0.25
Model 2: Multivariate adjusted‡
TotPow, ms2	3.6 (−0.6, 7.8)	0.095	2.0 (−2.4, 7.6)	0.31	2.0 (−5.4, 10.8)	0.53	0.95
ULF, ms2	2.2 (−2.4, 7.1)	0.34	1.0 (−4.4, 6.9)	0.70	1.0 (−7.7, 9.7)	0.88	0.91
VLF, ms2	6.1 (1.5, 11.0)	0.011	4.1 (−1.4, 10.0)	0.14	9.4 (1.6, 17.8)	0.02	0.36
LF, ms2	13.1 (6.4, 20.3)	<0.0001	7.3 (−0.8, 16.2)	0.08	19.7 (9.7, 31.3)	<0.0001	0.047
HF, ms2	6.3 (−0.9, 14.0)	0.09	2.0 (−7.0, 11.0)	0.73	6.2 (−4.6, 19.2)	0.24	0.25

^*Values are within-pair % geometric mean differences (95% CI) calculated from the β coefficient and expressed per 1-unit difference in the Mediterranean diet score comparing the twin with a higher score to his brother with a lower score.

^†Total energy intake (continuous), egg consumption (continuous), potato consumption (continuous).

^‡Demographic factors [education (continuous) and marital status (yes/no)]; lifestyle factors [physical activity (continuous)] and waist-to-hip ratio (continuous)]; coronary risk factors [Framingham risk score (continuous) and plasma triglycerides (continuous)]; use of fish oil supplements (yes/no), β-blockers (yes/no), and other medications (statins, aspirin, antihypertensives, and antihyperglycemics) (yes/no).