Aromatherapy May Improve Sleep Quality Among Patients in Cardiac Rehabilitation
Sleep disturbances are linked to cardiovascular diseases (CVDs), diabetes, and obesity. Poor sleep releases stress hormones that can contribute to CVD. Drugs often used by heart patients with poor sleep can cause substantial adverse effects (AEs). Aromatherapy with plant essential oils (EOs) has been found safe and effective in promoting good sleep in various settings. In a systematic review and meta-analysis, aromatherapy was found to significantly improve sleep, especially in unhealthy individuals.
Certain esters and alcohols found in EOs can reduce anxiety and promote sleep. Linalool, an alcohol found in many EOs including lavender (Lavandula spp., Lamiaceae), inhibits binding of glutamate receptors in the brain, with sedative, potentially neuroprotective effects. Although their mechanism of action is not well known, esters are perceived in aromatherapy as nervous system regulators, with ester-rich EOs considered the most relaxing and calming. Benzyl acetate, an ester of benzyl alcohol and acetic acid, is found in ylang-ylang (Cananga odorata, Annonaceae) EO. Linalyl acetate and geranyl acetate, two esters in lavender, are used as flavoring agents; the former, also in bergamot orange (Citrus bergamia, Rutaceae), is antimicrobial. Geranyl acetate, besides its potential sedative effect, masks perception of floral scents, perhaps making intense odors used in aromatherapy more tolerable.
The authors hypothesized that patients in a cardiac rehabilitation program who inhaled EOs high in linalool and esters would have better sleep than those not exposed. A randomized, double-blind, placebo-controlled, crossover trial (RCT) was conducted with outpatients of Texas Health Harris Methodist Hospital’s (Ft. Worth, Texas) cardiac rehabilitation service. Participants, recruited via flyers and by program nurses, were English speakers >18 years old. Asthma and nut allergies were exclusion criteria. Of 101 eligible, 50 (women, n = 12) aged 43-85 years (mean = 67) consented and were randomized to two groups of 25 each; 42 (women, n = 12) completed the study. It is not stated whether participants who did not complete the study completed intervention or placebo treatment.
The intervention agent included lavandin (L. × intermedia), bergamot orange, and ylang-ylang EOs (all from Nature’s Gift; Madison, Tennessee), described as organic and medical grade. One drop of each, undiluted, was placed on sterile cotton (Gossypium herbaceum, Malvaceae) balls. Three drops of an organic, roasted walnut (Juglans spp., Juglandaceae) EO (La Tourangelle; Berkeley, California) were used on placebo cotton balls. Intervention and placebo cotton balls were infused with jojoba (Simmondsia chinensis, Simmondsiaceae) EO. Intervention and placebo oils were similar in color, with aromas “vague enough” to deter identification. Three oil-infused cotton balls of either type were placed in black mesh fabric bags to further obscure color differences. Each mesh bag was placed in a resealable plastic bag with identical instructions for use. Participants received one bag of their assigned agent for each treatment period. They placed the mesh bag six to 36 inches from their pillow before retiring for five consecutive nights, re-sealing it in the plastic bag on rising. After a one-week wash-out period, the intervention group switched to placebo and vice versa for five nights, using the same routine. Adherence, self-reported at the end of each treatment period, is not recorded.
At baseline and after each treatment period, participants completed the Pittsburgh Sleep Quality Index (PSQI). The PSQI uses 19 questions to yield a global score of 0-21. Lower scores indicate better sleep; scores >5, poor. Global improvement of three points is considered substantial. The PSQI is designed to assess sleepover a one-month period, but a modified version was used in this brief RCT. The primary outcome was PSQI global scores after intervention vs. placebo. Baseline PSQI scores were not significantly different between those who took the intervention or the placebo first, but participant characteristics and baseline PSQI scores are poorly reported. At baseline, initial insomnia did not affect most participants, but 50% had trouble sleeping through the night or woke up too early. This is substantially more than in reports of general insomnia, likely due to participants’ cardiac rehabilitation status. Mean global score after the intervention was 4.9, significantly better (P = 0.0001) than after placebo (mean = 8.0). Effect size (Cohen’s d) was 1.00, “very large.” Neither age nor gender significantly influenced scores. Sleep quality was rated significantly better (P = 0.03) after the intervention than after placebo. Participants specifically reported waking to urinate less frequently (P = 0.05) and less trouble falling asleep due to feeling cold (P = 0.05) after the intervention versus placebo. This suggests that they slept more deeply with the intervention, perhaps gaining restorative stage 3 non-rapid eye movement (non-REM) sleep. This is consistent with previous reports that lavender and other EOs enhance slow-wave activity in non-REM sleep. Stage 3 non-REM sleep diminishes with age, and its enhancement could benefit elders.
A safety committee of program nurses not otherwise involved with the RCT reported no AEs. Most often administered in medical settings by nurses, aromatherapy is well within their scope of practice. Ease of use and low costs support its incorporation in standard care. Primary limitations to this RCT were due to practical and financial considerations. For example, polysomnography, the “gold standard” of sleep measures, is not available for home settings; hence, self-reporting was used. Gas chromatography profiles were provided for intervention EOs, but any aromatic degradation over the study period was not measured. More research on plant EOs and sleep is suggested. The authors declare no funding or competing for financial interests.
McDonnell B, Newcomb P. Trial of essential oils to improve sleep for patients in cardiac rehabilitation. J Altern Complement Med. December 2019;25(12):1193-1199. DOI: 10.1089/acm.2019.0222.