Table 2.

Heart Rate Variability Parameters of the Study Subjects

Variables	Smokers (n = 75)	Nonsmokers (n = 73)	P
SDNN	54.2 ± 31	138.2 ± 61.7	<0.0001
SDANN	45.3 ± 20.2	116.6 ± 46.2	<0.0001
RMSSD	36.9 ± 18.1	48.7 ± 30.8	0.006
LF day	1520 ± 506	505 ± 431	<0.0001
LF night	1087 ± 416	543 ± 127	<0.0001
LF 24 hours	1313 ± 467	428 ± 325	<0.0001
HF day	263 ± 102	448 ± 404	<0.0001
HF night	319 ± 113	616 ± 138	0.003
HF 24 hours	278 ± 98	438 ± 154	0.005
LF/HF day	6.4 ± 3.0	1.4 ± 1.2	<0.0001
LF/HF night	3.6 ± 1.5	1.0 ± 1.2	<0.0001
LF/HF 24 hours	4.9 ± 1.9	1.2 ± 0.7	<0.0001

SDNN = standard deviation of all NN intervals; SDANN = standard deviation of the 5‐minute mean RR intervals; RMSSD = root mean square of successive differences; LF = low frequency; HF = high frequency.