Table 3.
Heart rate variability values measured during 5-min periods of rest and mental stress (Stroop test), following randomization to almond and control snacks.
| Control, nmax = 51 1 | Almond, nmax = 54 1 | Main Comparison between Groups at Endpoint 4 | p-Value between Groups at Endpoint | |||
|---|---|---|---|---|---|---|
| Baseline 2 | Endpoint | Baseline 2 | Endpoint | |||
| Resting | ||||||
| NN, ms | 1009 ± 166 | 1006 (977, 1035) | 1050 ± 146 | 1012 (984, 1040) | 6 (−34, 47) | 0.760 |
| HR | 60.1 ± 10.7 | 60.5 (58.7, 62.3) | 58.0 ± 7.6 | 61.0 (59.3, 62.7) | 0.5 (−2.0, 3.0) | 0.704 |
| rMSSD, ms | 32.6 (24.6) | 37.7 (34.0, 41.5) | 31.9 (25.7) | 37.2 (33.5, 40.8) | −0.6 (−5.8, 4.7) | 0.831 |
| SDNN, ms | 54 ± 27 | 49 (44, 544) | 47 ± 21 | 50 (45, 55) | 1 (−6, 8) | 0.740 |
| SD1/SD2 | 0.5 ± 0.3 | 0.4 (0.4, 0.5) | 0.4 ± 0.1 | 0.4 (0.4, 0.5) | 0 (−0.1, 0) | 0.651 |
| HF, ms 2 | 373 (631) | 599 (468, 730) | 322 (541) | 514 (391, 636) | −85 (−265, 95) | 0.348 |
| HFnu | 0.40 ± 0.17 | 0.41 (0.36, 0.46) | 0.41 ± 0.14 | 0.42 (0.37, 0.46) | 0.01 (−0.06, 0.07) | 0.871 |
| LF:HF | 1.5 (1.7) | 1.9 (1.5, 2.2) | 1.4 (1.3) | 1.9 (1.5, 2.2) | 0 (−0.5, 0.5) | 0.924 |
| Mental stress (Stroop test) | ||||||
| NN 3, ms | 888 ± 166 | 935 (907, 963) | 950 ± 127 | 924 (899, 950) | −11 (−49, 28) | 0.310 |
| HR3 | 68 ± 10 | 65.4 (63.5, 67.3) | 64 ± 8 | 66.2 (64.5, 67.9) | 0.8 (−1.8, 3.4) | 0.543 |
| rMSSD, ms | 38.2 ± 22.4 | 31.8 (27.1, 36.5) | 33.8 ± 14.0 | 34.0 (29.8, 38.2) | 2.2 (−4.1, 8.5) | 0.494 |
| SDNN, ms | 54 (32) | 44 (41, 47) | 45 (22) | 48 (44, 51) | 4 (−1, 8) | 0.137 |
| SD1/SD2 | 0.4 (0.2) | 0.4 (0.3, 0.4) | 0.4 (0.1) | 0.4 (0.4, 0.4) | 0 (0, 0.1) | 0.420 |
| HF, ms 2 | 394 (473) | 281 (197, 364) | 264 (495) | 405 (331, 480) | 124 (11, 237) | 0.031 * |
| HFnu | 0.31 ± 0.10 | 0.26 (0.22, 0.30) | 0.32 ± 0.12 | 0.32 (0.28, 0.35) | 0.06 (0, 0.11) | 0.040 * |
| LF:HF | 2.3 (1.5) | 3.6 (3.0, 4.3) | 2.0 (1.7) | 2.6 (2.0, 3.2) | −1.0 (−1.9, −0.1) | 0.023 * |
Endpoint values and main comparison between groups at endpoint are presented as mean (95% CI). 1 Not all data were analyzed due to technical problems. Resting NN, HR, rMSSD, SDNN and SD1/SD2: n = 40 (control) and 43 (almond). Resting HF, HFnu, and LF:HF: n = 35 (control) and 40 (almond). Mental stress (Stroop test) NN and HR: n = 35 (control) and 44 (almond). Mental stress (Stroop test) rMSSD, SDNN and SD1/SD2: n = 36 (control) and 44 (almond). Mental stress (Stroop test) HF, HFnu and LF:HF: n = 28 (control) and 35 (almond). 2 Mean ± SD for baseline data that are normally distributed. Median (IQR) for other data as they are non-normally distributed. 3 Baseline value was different between control and almond group; independent t-test was used for normally distributed data while Mann–Whitney U test was used for non-normally distributed data; p < 0.05 indicating a significant difference. 4 ANCOVA, adjusted for baseline outcome value and baseline BMI (mean difference almonds—control at endpoint). * p < 0.05. NN, normal-to-normal intervals; HR, heart rate; rMSSD, root mean square of successive R-R interval differences; SDNN, standard deviation of normal-to-normal (NN) intervals; HF, absolute power of the high-frequency band (0.15–0.04 Hz); HFnu, normalized HF (HFnu = HF/(HF + LF)).