Alzheimer's Disease Revisited: Do Aromatherapy Really Work?

Alzheimer’s disease, a condition that does not have any potential cure, needs to be managed. Explaining Alzheimer’s in terms of neurology is losing the sense of smell is one of the earliest Alzheimer's disease symptoms which ultimately leads to memory loss through nose-brain interface. However, evidence proves that aromatherapy can have a beneficial effect on Alzheimer's disease patients. Now, the question is how come “aromatherapy”, an approach where inhalation of essential oils is used for therapeutic purposes can benefit individuals who have lost the sense of smell (Mehta et al., 2022). 

This particular article focuses on understanding how aromatherapy influences the life of Alzheimer's patients and its direct effect on its independent factors associated with disease conditions.  

As per 2024 Alzheimer's disease facts and figures (2024), the prevalence of Alzheimer's among the old age population is increasing rapidly, and it is expected that by next 40 years the number of incident cases will be doubled and most important the death rate due to Alzheimer’s has increased more than 140% and in the near future this is going to increase steeply. The incidence of Alzheimer's dementia is gradually increasing and the costs of medical bills of these patients around 2024 was $360 billion which is expected to hike every year. As a result, it is of utmost importance to find out some immediate ways which might prevent or delay the occurrence of the disease in patients. Additionally, approaches that can soothe and control disease conditions are also needed. 

The primary concerns for Alzheimer’s disease incidence include lifestyle conditions like stress, anxiety, loneliness or social isolation, diet and co-morbidities like diabetes mellitus, hypertension, obesity, and so on. Other than this, the genetic factors also hold its significance (Li et al., 2023; John et al., 2021). Therefore, an individual’s lifestyle, diet, history of diseases, and family history all play a significant role in the disease occurrence and progression.  

Due to lack of mental health awareness, most of the individuals are unaware of this connection between mental stress management, anxiety disorder and dementia The connection between chronic stress and Alzheimer's has been studied in multiple research works, there is large-scale population data depicting these mental health conditions are linked to such neurodegenerative diseases. A Swedish cohort study following over 1.36 million adults found that individuals diagnosed with chronic stress had more than double the risk of developing Alzheimer's disease (odds ratio 2.45), while those diagnosed with depression carried a similarly elevated risk (odds ratio 2.32). Critically, individuals with both chronic stress and depression together had a four-fold increased risk compared to those with neither condition (Wallensten et al., 2023). 

Mechanistically, chronic stress keeps the body's hypothalamic-pituitary-adrenal (HPA) axis persistently activated, leading to sustained elevation of cortisol. Over the years, this chronic cortisol exposure is understood to damage the hippocampus, the region of the brain responsible for forming new memories, and one of the earliest structures affected by Alzheimer's disease. Anxiety and depression compound this effect further, both by prolonging the body's stress response and through their own independent associations with faster cognitive decline. Therefore, it is understandable that stress management and brain health development are inter-linked and independent factors that contribute to dementia. 

As it is highlighted earlier, although Alzheimer's primary symptom is losing the sense of smell, aromatherapy has a beneficial effect on it and might have significant value in incorporating it as an alternative to Alzheimer's treatment. As chronic stress, anxiety, and depression are modifiable risk factors, interventions that genuinely reduce them hold importance, and this is where aromatherapy is considered. Lavender oil is among the most studied essential oils for anxiety relief, shown across multiple trials to lower self-reported anxiety and physiological stress markers when inhaled and hence can be used for stress relief or as an alternative anxiety treatment. Bergamot oil has demonstrated mood-lifting and cortisol-modulating effects. Rosemary, meanwhile, is associated with heightened alertness and concentration.

The mechanism behind all of this traces back to the same nose-brain interface discussed earlier: inhaled aromatic compounds reach the limbic system, the brain's emotional processing center, directly and quickly, without first passing through the slower conscious-reasoning pathways that, say, a spoken reassurance or a distraction technique would need to take. This is precisely why aromatherapy integrates so naturally into daily lifestyle routines rather than requiring a clinical setting: a few drops of lavender in a diffuser before bed, bergamot during a stressful workday, or rosemary during a study or focus session are low-cost, low-risk additions that directly target the same biological stress pathways implicated in dementia risk. 

The decline of olfactory in Alzheimer's disease is progressive, not immediate. It typically begins often years before major memory symptoms appear and worsens gradually as the disease advances. This means particularly in the pre-symptomatic and early stages, where the sense of smell is still functional. Application of aromatherapy can help in engaging the brain's limbic and memory circuitry. Furthermore, when the condition worsens, aromatherapy does not rely solely on the olfactory nerve. Many essential oils, particularly stronger ones like rosemary, lavender, and lemon, also stimulate the trigeminal nerve, a separate cranial nerve responsible for sensations like coolness, warmth, and intensity in the nasal passage. This trigeminal pathway remains active even when fine-grained smell discrimination is impaired. This actually has been found to be helpful for soothing or calming patients with advanced dementia or Alzheimer’s. In short, aromatherapy's benefit in Alzheimer's disease is strongest as an early and preventive tool, but it retains a physiological pathway to act even after smelling itself has begun to fade (Lin et al., 2024; Fong et al., 2024; Ballard et al., 2002). Therefore, aromatherapy can help in calming the patients of Alzheimer’s disease by these three ways:

1. Losing residual smell capacity: Patients who have impaired smelling ability can still retain some smell function, and that residual capacity is enough to engage the limbic and memory system. 

2. Topical absorption. Certain essential oils can be applied topically through massage by diluting it with carrier oils. As it can be absorbed and exert calming or physiological effects without needing to be inhaled or consciously perceived as a scent at all. 

3. Psychological and environmental effects. There is also a physiological backup pathway which is used by many essential oils, particularly stronger ones like rosemary, lavender, and lemon. These oils stimulate the trigeminal nerve by calming or stimulating effects have still been observed in patients with more advanced dementia. 

It's worth noting that not every review has been as unambiguously positive. A 2020 Cochrane systematic review found the existing trial evidence too limited and inconsistent in quality to draw firm conclusions, underscoring that this remains an evolving field rather than settled science (Ball et al., 2020). Additionally, neither evidence suggests aromatherapy can cure or reverse Alzheimer's disease. But as a low-risk, low-cost complementary approach, aromatherapy has earned a legitimate place in Alzheimer’s or dementia care.

Therefore, depending on the disease symptoms of the patients, an essential oil can be used in either of the three ways mentioned above. A general routine is provided below: 

• Rosemary and Lemon oil diffused in the morning to support alertness and concentration 

• Lavender and Orange oil diffused in the evening to calm the nervous system and support sleep 

• For agitation or acute anxiety specifically, a diluted Melissa officinalis (Lemon balm) application is considered 

As with any essential oil use, particularly for older adults or those with dementia, oils should be properly diluted, diffused for limited periods rather than continuously, and discussed with a physician beforehand.

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