Background to the review
Medication prescribed for the treatment of dementia is not always effective at relieving symptoms of the condition such as problems with thinking, behaviour, mood, and sleep. Natural therapies, including aromatherapy (the use of fragrant essential oils from plants), are attractive options for treating these distressing symptoms of dementia as they are often thought to have a low risk of side effects.
Review question
Is aromatherapy safe and effective at relieving symptoms of dementia?
What we did
We searched the medical literature up to 5 May 2020, looking for studies which compared aromatherapy for people with dementia to a control treatment, which could be either usual care or ‘dummy’ aromatherapy involving a non-fragrant oil. To make the comparison fair, the studies had to assign people randomly to aromatherapy or to the control treatment. We looked at the effect on agitation, behavioural and mental health issues, and other important symptoms of dementia. We also looked for reports of side effects. Because the studies were so different from each other, we were not able to combine results statistically so we described the results of individual studies and assessed how confident we could be in them.
Study characteristics
We found 13 studies to include in the review. There were 708 participants in total. All had dementia and were living in care homes. The most commonly used aromatherapy fragrance was lavender. Studies also used lemon balm, orange and cedar extracts.
Main findings
Ten studies assessed agitation, but five did not report data we could use or our confidence in their results was very low. We had moderate or low confidence in the results of the other five: four reported no significant effect of aromatherapy and one reported a significant benefit. Eight studies assessed behavioural and mental health issues, but three did not report any usable data, or our confidence in the results was very low. Of the other five, for which our confidence was moderate or low, four reported a significant benefit from aromatherapy and one reported no significant effect. Side effects of treatment were either poorly reported or not reported at all. No more than three studies reported our secondary outcomes which were quality of life, cognition (thinking), mood, sleep, activities of daily living, and caregiver burden. We found no evidence that aromatherapy was helpful for any of these outcomes.
Quality of the evidence
Overall the quality of the evidence was poor. Many of the studies were poorly reported and some did not report any data we could use. Most studies were very small so that there was a lot of uncertainty about their results. Results of different studies did not agree with one another.
Conclusions
We have found no convincing evidence that aromatherapy is beneficial for people with dementia although there are many limitations to the data reported by the studies so conclusions cannot be drawn with confidence. In order to determine whether aromatherapy is safe and effective at relieving symptoms of dementia, larger, well-designed studies with clearer reporting are needed.
We have not found any convincing evidence that aromatherapy (or exposure to fragrant plant oils) is beneficial for people with dementia although there are many limitations to the data. Conduct or reporting problems in half of the included studies meant that they could not contribute to the conclusions. Results from the other studies were inconsistent. Harms were very poorly reported in the included studies. In order for clear conclusions to be drawn, better design and reporting and consistency of outcome measurement in future trials would be needed.
Medications licensed for the treatment of dementia have limited efficacy against cognitive impairment or against the distressed behaviours (behavioural and psychological symptoms, or behaviour that challenges) which are also often the most distressing aspect of the disorder for caregivers. Complementary therapies, including aromatherapy, are attractive to patients, practitioners and families, because they are perceived as being unlikely to cause adverse effects. Therefore there is interest in whether aromatherapy might offer a safe means of alleviating distressed behaviours in dementia.
To assess the efficacy and safety of aromatherapy for people with dementia.
We searched ALOIS, the Cochrane Dementia and Cognitive Improvement Group Specialized Register, on 5 May 2020 using the terms: aromatherapy, lemon, lavender, rose, aroma, alternative therapies, complementary therapies, essential oils. In addition, we searched MEDLINE, Embase, PsycINFO (all via Ovid SP), Web of Science Core Collection (via Thompson Web of Science), LILACS (via BIREME), CENTRAL (via the Cochrane Library), ClinicalTrials.gov and the World Health Organization (WHO) trials portal (ICTRP) on 5 May 2020.
We included randomised controlled trials which compared fragrance from plants in an intervention defined as aromatherapy for people with dementia with placebo aromatherapy or with treatment as usual. All doses, frequencies and fragrances of aromatherapy were considered. Participants in the included studies had a diagnosis of dementia of any subtype and severity.
Two reviewers independently selected studies for inclusion, extracted data and assessed risk of bias in included studies, involving other authors to reach consensus decisions where necessary. We did not perform any meta-analyses because of heterogeneity between studies, but presented a narrative synthesis of results from the included trials. Because of the heterogeneity of analysis methods and inadequate or absent reporting of data from some trials, we used statistical significance (P ≤ or > 0.5) as a summary metric when synthesising results across studies. As far as possible, we used GRADE methods to assess our confidence in the results of the trials, downgrading for risk of bias and imprecision.
We included 13 studies with 708 participants. All participants had dementia and in the 12 trials which described the setting, all were resident in institutional care facilities. Nine trials recruited participants because they had significant agitation or other behavioural and psychological symptoms in dementia (BPSD) at baseline. The fragrances used were lavender (eight studies); lemon balm (four studies); lavender and lemon balm, lavender and orange, and cedar extracts (one study each). For six trials, assessment of risk of bias and extraction of results was hampered by poor reporting. Four of the other seven trials were at low risk of bias in all domains, but all were small (range 18 to 186 participants; median 66), reducing our confidence in the results. Our primary outcomes were agitation, overall behavioural and psychological symptoms, and adverse effects. Ten trials assessed agitation using various scales. Among the five trials for which our confidence in the results was moderate or low, four trials reported no significant effect on agitation and one trial reported a significant benefit of aromatherapy. The other five trials either reported no useable data or our confidence in the results was very low. Eight trials assessed overall BPSD using the Neuropsychiatric Inventory and we had moderate or low confidence in the results of five of them. Of these, four reported significant benefit from aromatherapy and one reported no significant effect. Adverse events were poorly reported or not reported at all in most trials. No more than two trials assessed each of our secondary outcomes of quality of life, mood, sleep, activities of daily living, caregiver burden. We did not find evidence of benefit on these outcomes. Three trials assessed cognition: one did not report any data and the other two trials reported no significant effect of aromatherapy on cognition. Our confidence in the results of these studies was low.