Olfactory Training Shows Favorable Pain Sensitivity Outcomes in Children With Primary Headache

Training with odors had a positive effect on olfactory function, pain thresholds, and sleep quality among children and adolescents with primary headache, according to study results published in Frontiers in Pain Research.

The study included 80 pediatric patients with migraine or tension-type headache at the Pain Center of the University Hospital Dresden in Germany. The first 40 patients who were successfully enrolled received olfactory training and the subsequent 40 patients received outpatient therapy. The olfactory training group received 2 daily exposures to 3 pleasant odors out of a total of 11 odors selected at baseline. The participants were evaluated for olfactory function using Sniffin’ Sticks testing, headache frequency, Pediatric Migraine Disability Assessment (PedMIDAS), and Pediatric Pain Disability Index outcomes at baseline and at 3 months.

The olfactory and control cohorts included patients with a mean age of 13.83 (SD, 3.18) and 12.38 (SD, 3.27) years; 60% and 67.5% were girls; 35% and 42.5% had mixed headaches; and they had an average of 30.5 (SD, 27.1) and 33.1 (SD, 31.5) headache days in the last 3 months, respectively. Among all participants, 35% had comorbidities, the most common of which were allergic asthma (14%), back pain (11%), and depression (11%).

After olfactory training, Threshold, Discrimination, Identification (TDI) scores improved (t_[39], -2.851; P =.007) and differed significantly from the TDI scores of the control cohort (Mann-Whitney U, 540.500; P =.01).

Patients who received olfactory training had significant changes to mechanical detection threshold scores (z, -2.354; P =.019) whereas no change was observed among controls (z, -0.37; P =.712). Electrical pain thresholds were significantly increased among olfactory training recipients (z, -2.217; P =.027) and decreased among the control group (z, -2.283; P =.022).

In addition, olfactory training was associated with significant improvements to sleep quality (t_[39], 2.184; P =.035), whereas sleep quality tended to be aggravated in the control group (t_[39], -1.924; P =.062). Similarly, mood quality improved in the olfactory group (t_[39], 2.109; P =.041) but not in the control group (t_[39], 0.376; P =.071).

The changes in TDI ratio and electrical pain threshold were significantly correlated (P =.021).

Overall, patients reported a decrease in the average number of headache days during the study. The greatest reduction was observed among children aged 6 to 9 years (mean difference [MD], -21.8 days), followed by adolescents aged 13 to 15 years (MD, -7.7 days), 10 to 12 years (MD, -4.3 days), and 16 to 19 years (MD, -2.1 days). No group differences in headache frequency (P =.25) or medication intake (P =.2) were observed.

Limitations of this study included a lack of placebo control and the presence of selection bias as patients self-reported as nonosmophobic. Moreover, the younger average age among the control cohort may have led to a larger placebo effect.

 “Olfactory training is a well-tolerated and inexpensive nonpharmacological treatment option that might positively influence childhood headaches,” the study authors concluded.