**4. Heart rate variability and oral contraceptives**

Third-generation combined oral contraceptives (COCs) containing desogestrel and gestodene (GEST) were introduced to reduce adverse effects such as fluid retention, nausea, headaches, and weight changes (Arangino et al., 1998; Read, 2010). The balance of risks and benefits of COC use varies, depending on patterns of usage and background risk of disease (Hannaford et al., 2010). The repercussions of COCs on cardiac autonomic modulation have not yet been thoroughly investigated. Studies reveal that female sex hormones influence cardiovascular autonomic function (Minson et al., 2000; Neves et al., 2007; Carter et al., 2009). Leicht et al. (2003) reported a positive correlation between circulating estrogen levels and HRV.

Furthermore, the cardioprotective effects of endogenous estrogen through vasodilation and inhibition of blood vessel injuries have been reported (Mendelsohn & Karas, 1999). Low levels of estrogen are associated with a reduction of cardiac autonomic modulation (Moodithaya 2009). Large clinical trials have shown that the long-term use of estrogen in combination with a progestogen may not be beneficial, and could even compromise the efficiency of autonomic HR modulation. Minson et al. (2000) confirmed that COC use can modify baroreflex sensitivity and sympathetic activity. However, Santos et al. (2008) and Schueller et al. (2006) found that COC users and non-users showed similar HRV indices.

174 Fourier Transform Applications

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 **Frequency (Hz)**

Fig. 3. Power spectrum of the analysis of HRV obtained by applying an autoregressive model to a dataset of 256 values of R-R intervals in the supine position from one of the volunteers of this study, showing the VLF (light gray), LF (medium gray) and HF (dark

Third-generation combined oral contraceptives (COCs) containing desogestrel and gestodene (GEST) were introduced to reduce adverse effects such as fluid retention, nausea, headaches, and weight changes (Arangino et al., 1998; Read, 2010). The balance of risks and benefits of COC use varies, depending on patterns of usage and background risk of disease (Hannaford et al., 2010). The repercussions of COCs on cardiac autonomic modulation have not yet been thoroughly investigated. Studies reveal that female sex hormones influence cardiovascular autonomic function (Minson et al., 2000; Neves et al., 2007; Carter et al., 2009). Leicht et al. (2003) reported a positive correlation between circulating estrogen levels

Furthermore, the cardioprotective effects of endogenous estrogen through vasodilation and inhibition of blood vessel injuries have been reported (Mendelsohn & Karas, 1999). Low levels of estrogen are associated with a reduction of cardiac autonomic modulation (Moodithaya 2009). Large clinical trials have shown that the long-term use of estrogen in combination with a progestogen may not be beneficial, and could even compromise the efficiency of autonomic HR modulation. Minson et al. (2000) confirmed that COC use can modify baroreflex sensitivity and sympathetic activity. However, Santos et al. (2008) and Schueller et al. (2006) found that COC users and non-users showed similar HRV

**4. Heart rate variability and oral contraceptives** 

150

100

50

**Power spectral density (ms )**

gray) bands

and HRV.

indices.

 **2**

0

Carter et al. (2009) observed no effects of OC use on the sympathetic modulation of the heart during orthostatic stress, nor differences in that regard between the phase of intake of active pills and that of intake of inactive pills. Women with greater physical activity, both users and non-users of OCs, showed a predominance of parasympathetic modulation and presented a greater complexity of pattern distribution and less regularity and predictability of sequential patterns than sedentary groups. Wenner et al. (2006) evaluated amenorrheic and eumenorrheic athletes who were users and non-users of OCs, and observed no influence on cardiac autonomic function. However, other studies suggest that there is a relationship between OC use and autonomic HR modulation, which the authors attribute to changes in vagal peripheral modulation caused by high levels of circulating estrogen (Minson, 2000; Leicht et al., 2003).

Santos et al. (2008) analyzed the autonomic modulation of HR based on frequency domain (LF, HF and LF/HF) indices and found that the use of contraceptives did not affect the results, since they detected no difference among the groups under study. This finding may be attributed to the pharmacological properties of low estrogen/progesterone dosages, as well as to the maintenance of the integrity of the autonomic modulation of HR, since the values found here fall within the range of normality. The results of this study suggest that low estrogen/progesterone dosages do not impair autonomic modulation in the age group under study.
