. 2016 Oct 5;7:1536. doi: 10.3389/fpsyg.2016.01536

Table 2.

Bivariate correlations between study variables.

Variable		SDNN	QT VI	RMSSD	HF HRV	Letter digit	RS, span score	RS, FRC	Stroop inhibition, RT	Stroop shifting, RT	2-Back, RT	2-Back, Accuracy	TMT A (s)	TMT B (s)	TMT B–TMT A (s)	MDI	SMBQ	Age	Income	Phys. activity	Sex	Edu. level
SDNN	Pearson's r	1
	Sig. (1-tailed)
	N	119
QT VI	Pearson's r	−0.427^**	1
	Sig. (1-tailed)	0.000
	N	114	114
RMSSD	Pearson's r	0.787^**	−0.426^**	1
	Sig. (1-tailed)	0.000	0.000
	N	119	114	119
HF HRV	Pearson's r	0.478^**	−0.291^**	0.649^**	1
	Sig. (1-tailed)	0.000	0.001	0.000
	N	118	114	118	118
Letter digit	Pearson's r	0.191^*	−0.177^*	0.177^*	0.013	1
	Sig. (1-tailed)	0.019	0.031	0.027	0.444
	N	118	113	118	117	118
Reading span, span score	Pearson's r	−0.021	−0.059	0.027	−0.010	0.261^**	1
	Sig. (1-tailed)	0.412	0.271	0.389	0.456	0.002
	N	115	110	115	114	115	115
Reading span, FRC	Pearson's r	−0.002	−0.067	0.067	−0.011	0.392^**	0.717^**	1
	Sig. (1-tailed)	0.492	0.243	0.239	0.455	0.000	0.000
	N	116	111	116	115	116	115	116
Stroop inhibition, RT	Pearson's r	−0.225^**	0.287^**	−0.247^**	−0.111	−0.541^**	−0.131	−0.192^*	1
	Sig. (1-tailed)	0.008	0.001	0.004	0.123	0.000	0.086	0.021
	N	113	108	113	112	113	111	112	113
Stroop shifting, RT	Pearson's r	−0.184^*	0.264^**	−0.222^**	−0.085	−0.485^**	−0.193^*	−0.320^**	0.785^**	1
	Sig. (1-tailed)	0.025	0.003	0.009	0.186	0.000	0.021	0.000	0.000
	N	114	109	114	113	114	112	113	113	114
2-Back, RT	Pearson's r	−0.134	0.228^**	−0.076	0.040	−0.442^**	−0.197^*	−0.208^*	0.326^**	0.400^**	1
	Sig. (1-tailed)	0.075	0.008	0.206	0.336	0.000	0.018	0.013	0.000	0.000
	N	117	112	117	116	117	114	115	112	113	117
2-Back, Accuracy	Pearson's r	0.062	−0.198^*	0.119	−0.014	0.297^**	0.173^*	0.202^*	−0.232^**	−0.227^**	−0.386^**	1
	Sig. (1-tailed)	0.254	0.018	0.101	0.442	0.001	0.033	0.015	0.007	0.008	0.000
	N	117	112	117	116	117	114	115	112	113	117	117
TMT A (s)	Pearson's r	−0.185^*	0.238^**	−0.156^*	−0.115	−0.621^**	−0.273^**	−0.286^**	0.385^**	0.414^**	0.390^**	−0.258^**	1
	Sig. (1-tailed)	0.022	0.005	0.045	0.108	0.000	0.002	0.001	0.000	0.000	0.000	0.002
	N	119	114	119	118	118	115	116	113	114	117	117	119
TMT B (s)	Pearson's r	−0.275^**	0.183^*	−0.246^**	0.035	−0.486^**	−0.285^**	−0.378^**	0.362^**	0.391^**	0.339^**	−0.365^**	0.401^**	1
	Sig. (1-tailed)	0.001	0.026	0.003	0.352	0.000	0.001	0.000	0.000	0.000	0.000	0.000	0.000
	N	119	114	119	118	118	115	116	113	114	117	117	119	119
TMT B–TMT A (s)	Pearson's r	−0.227^**	0.108	−0.206^*	0.084	−0.282^**	−0.197^*	−0.293^**	0.228^**	0.248^**	0.215^**	−0.296^**	0.040	0.932^**	1
	Sig. (1-tailed)	0.007	0.127	0.012	0.183	0.001	0.018	0.001	0.008	0.004	0.010	0.001	0.332	0.000
	N	119	114	119	118	118	115	116	113	114	117	117	119	119	119
MDI, rating	Pearson's r	0.128	−0.070	0.143	0.324^**	−0.065	−0.053	−0.177^*	0.029	0.104	0.031	−0.042	−0.096	0.035	0.076	1
	Sig. (1-tailed)	0.083	0.230	0.060	0.000	0.243	0.288	0.029	0.379	0.135	0.369	0.327	0.149	0.353	0.205
	N	119	114	119	118	118	115	116	113	114	117	117	119	119	119	119
SMBQ	Pearson's r	0.084	−0.014	0.081	0.276^**	−0.121	−0.102	−0.180^*	0.051	0.108	0.049	−0.031	−0.105	0.097	0.147	0.845^**	1
	Sig. (1-tailed)	0.183	0.443	0.190	0.001	0.095	0.140	0.026	0.294	0.127	0.300	0.372	0.128	0.148	0.055	0.000
	N	119	114	119	118	118	115	116	113	114	117	117	119	119	119	119	119
Age	Pearson's r	−0.315^**	0.193^*	−0.424^**	−0.455^**	−0.296^**	−0.174^*	−0.182^*	0.355^**	0.417^**	0.294^**	−0.168^*	0.409^**	0.327^**	0.194^*	−0.230^**	−0.186^*	1
	Sig. (1-tailed)	0.000	0.020	0.000	0.000	0.001	0.031	0.025	0.000	0.000	0.001	0.035	0.000	0.000	0.017	0.006	0.022
	N	119	114	119	118	118	115	116	113	114	117	117	119	119	119	119	119	119
Income	Pearson's r	−0.090	0.036	−0.156^*	−0.148	−0.007	0.083	0.086	0.091	0.100	−0.042	−0.056	0.056	0.004	−0.017	−0.140	−0.152^*	0.282^**	1
	Sig. (1-tailed)	0.164	0.351	0.045	0.055	0.468	0.188	0.178	0.168	0.145	0.325	0.276	0.271	0.481	0.425	0.064	0.049	0.001
	N	119	114	119	118	118	115	116	113	114	117	117	119	119	119	119	119	119	119
Physical activity	Pearson's r	0.054	−0.069	0.075	0.014	0.006	−0.060	−0.045	−0.062	0.020	−0.109	0.065	0.135	−0.103	−0.166^*	0.037	−0.052	0.139	0.073	1
	Sig. (1-tailed)	0.279	0.233	0.210	0.441	0.475	0.262	0.316	0.256	0.416	0.121	0.243	0.071	0.132	0.035	0.344	0.286	0.065	0.215
	N	119	114	119	118	118	115	116	113	114	117	117	119	119	119	119	119	119	119	119
Sex	Spearman's rho	0.179^*	−0.114	0.228^**	0.253^**	0.215^**	0.022	0.116	−0.244^**	−0.245^**	−0.053	0.212^*	−0.004	−0.173^*	−0.212^*	0.029	0.020	−0.159^*	−0.219^**	0.094	1
	Sig. (1-tailed)	0.026	0.114	0.006	0.003	0.010	0.407	0.108	0.005	0.004	0.283	0.011	0.484	0.030	0.010	0.378	0.414	0.042	0.008	0.154
	N	119	114	119	118	118	115	116	113	114	117	117	119	119	119	119	119	119	119	119	119
Educational level	Spearman's rho	0.112	−0.077	0.025	−0.018	0.080	0.054	0.104	−0.149	−0.076	−0.037	0.011	0.046	−0.086	−0.126	−0.085	−0.132	0.009	0.206^*	0.184^*	0.059	1
	Sig. (1-tailed)	0.113	0.207	0.394	0.425	0.196	0.282	0.133	0.057	0.211	0.347	0.453	0.310	0.176	0.086	0.180	0.076	0.460	0.012	0.022	0.263
	N	119	114	119	118	118	115	116	113	114	117	117	119	119	119	119	119	119	119	119	119	119
SCC	Pearson's r	0.132	−0.013	0.110	0.291^**	−0.163	−0.137	−0.226^*	0.102	0.175	0.092	−0.082	−0.067	0.163	0.204^*	0.813^**	0.912^**	−0.163	−0.16	−0.035	−0.034	−0.144
	Sig. (1-tailed)	0.155	0.889	0.234	0.001	0.079	0.146	0.015	0.286	0.064	0.326	0.381	0.473	0.078	0.026	0.000	0.000	0.08	0.084	0.705	0.357	0.06
	N	118	113	118	117	117	114	115	112	113	116	116	118	118	118	118	118	118	118	118	118	118

^**

Correlation is significant at the 0.01 level (1-tailed).

Correlation is significant at the 0.05 level (1-tailed).

Significant correlations between cardiovascular autonomic regulation measures and cognitive measures are printed in bold.

SDNN, standard deviation of the inter-heart-beat interval; QT VI, cardiac repolarization variability index; RMSSD, root of the mean squares of inter-heart-beat intervals; HF HRV, high frequency band heart rate variability; RS, Reading span; Total FRC, number of words in the test that were Freely Recalled Correctly; MDI, major depression inventory; SMBQ, Shirom Melamed Burnout Questionnaire; SCC, subjective cognitive complaints.