Group |
BPPV (N=52) |
AUD (N=72) |
p |
Age, years |
49.5 ± 11.2 |
43.5 ± 14.1 |
0.012 |
Sex (%) |
0.586 |
||
Female |
33 (63.5%) |
41 (56.9%) |
|
Male |
19 (36.5%) |
31 (43.1%) |
|
Symptom duration, days |
6.9 ± 10.7 |
13.2 ± 10.5 |
0.001 |
DHI |
21.8 ± 15.6 |
22.9 ± 18.4 |
0.739 |
FSS |
2.2 ± 1.7 |
3.1 ± 1.9 |
0.008 |
ISI |
7.2 ± 5.2 |
9.1 ± 6.7 |
0.085 |
BAI |
10.6 ± 9.2 |
15.8 ± 12.3 |
0.008 |
BDI-II |
9.9 ± 8.2 |
12.8 ± 9.4 |
0.083 |
BPPV, benign paroxysmal positional vertigo; AUD, acute unexplained dizziness; DHI, Dizziness Handicap Inventory; FSS, Fatigue Severity Scale; ISI, Insomnia Severity Index; BAI, Beck Anxiety Index; BDI-II, Beck Depression Index-II. |
Correlations between the DHI score and other variables in the AUD group are shown in Table 2. The fatigue, insomnia, anxiety, and depression scores each had a significant positive correlation with the DHI score (p=0.001), while age and symptom duration did not (p=0.092 and 0.688, respectively) (Table 2). The FSS score correlated with the ISI score in the AUD group, but this correlation was not seen in the BPPV group (data not shown). The predictors for the DHI score in the AUD group are shown in Table 3. Multivariate analyses delineated the strongest predictor as the BAI (ß=0.495, p=0.002), followed by the FSS (ß=0.249, p=0.027) (Table 3).
Variable differences after fatigue treatment in the AUD group are shown in Table 4. In the AUD group, follow-up data were collected on the second visit after education and medications were provided to the patients to relieve fatigue or sleep-related problems. Only 19 patients in the AUD group had the second visit within 7 to 14 days after the first visit. The rest of the patients declined to return to our clinic because their dizziness rapidly disappeared and they did not feel that a return visit was necessary. The follow-up data showed significant improvement not only in the DHI score, but also in the FSS and BAI scores compared to those from the initial visits (p=0.03, 0.009, and 0.01, respectively) by the paired t-test (Table 4).
Table 2. Pearson’s correlations between the DHI and variables in patients with AUD. The fatigue, insomnia, anxiety, and depression scores each had a significant positive correlation (p=0.001) with the DHI score, while age and symptom duration did not (p=0.092 and 0.688 respectively).
r |
p |
|
Age |
–0.200 |
0.092 |
Symptom duration |
0.048 |
0.688 |
FSS |
0.527 |
<0.001 |
ISI |
0.438 |
<0.001 |
BAI |
0.65 |
<0.001 |
BDI-II |
0.552 |
<0.001 |
DHI, Dizziness Handicap Inventory; AUD, acute unexplained dizziness; FSS, Fatigue Severity Scale; ISI, Insomnia Severity Index; BAI, Beck Anxiety Index; BDI-II, Beck Depression Index-II. Bold face indicates statistical significance. |
Table 3. Multiple regression analysis of variables associated with the DHI in patients with AUD. The strongest predictor was the BAI (ß=0.495, p=0.002), followed by the FSS (ß=0.249, p=0.027).
Variable |
Standardized coefficient (ß) |
p |
Collinearity VIF |
R2 |
Constant |
<0.001 |
0.469 |
||
FSS |
0.249 |
0.027 |
1.519 |
|
ISI |
0.093 |
0.427 |
1.715 |
|
BAI |
0.495 |
0.002 |
3.08 |
|
BDI-II |
-0.45 |
0.785 |
3.409 |
|
DHI, Dizziness Handicap Inventory; AUD, acute unexplained dizziness; FSS, Fatigue Severity Scale; ISI, Insomnia Severity Index; BAI, Beck Anxiety Index; BDI-II, Beck Depression Index-II. |
Table 4. Variable differences in the 7 to 14-day interval after symptom onset in patients with AUD. Significant improvement was observed in DHI, FSS, and BAI scores compared with those from the initial visits (p=0.03, 0.009, and 0.010, respectively) by the paired t-test.
Variables |
Visit 1 (N=19) |
Visit 2 (N=19) |
p |
DHI |
26.3 ± 17.3 |
15.0 ± 13.6 |
0.03 |
FSS |
3.5 ± 1.9 |
2.5 ± 1.6 |
0.009 |
ISI |
10.2 ± 7.7 |
8.9 ± 6.7 |
0.228 |
BAI |
20.6 ± 15.1 |
13.6 ± 11.4 |
0.01 |
BDI-II |
17.3 ± 11.7 |
13.9 ± 11.8 |
0.071 |
AUD, acute unexplained dizziness; DHI, Dizziness Handicap Inventory; FSS, Fatigue Severity Scale; ISI, Insomnia Severity Index; BAI, Beck Anxiety Index; BDI-II, Beck Depression Index-II. Paired t-test was used. |
The patients in the AUD group showed distinct clinical characteristics. The patients were usually sleep-deprived or overworked (e.g., shift workers, students preparing for college, mothers or grandmothers taking care of their young children or grandchildren). The symptoms were a sense of floating or unsteadiness starting 1 or 2 hours after waking up or working at the jobsite.
The dizziness lasted all day with fluctuating but slowly increasing intensity over time and worst in the late afternoon. In some patients, the dizziness lasted several minutes (usually 1 to 10 minutes) followed by a symptom-free period lasting several minutes, with the dizziness cycle occurring several times an hour. Pain in the head and neck sometimes accompanied the dizziness, but nausea did not. The dizziness usually disappeared while the patients were concentrating on certain activities such as driving a car, operating tools, or conversing with others. The dizziness also resolved after returning home in the evening or when rest was guaranteed.
Discussion
The AUD group presented with a higher fatigue score compared to the BPPV group; therefore, we postulate that fatigue may be related causally to dizziness. The higher fatigue score of the AUD group might result from insomnia, as indicated by our finding that fatigue severity correlated with insomnia severity. This accords with a previous report that the most common cause of fatigue was insufficient sleep, and the most common cause of insufficient sleep was determined to be too little time to sleep (Broman et al., 1996). Sleep problems were reported by 65.0% of the patients with fatigue in a primary care unit (Nijrolder et al., 2009). Modern lifestyle encourages later bedtimes and longer hours of nighttime arousal (Shochat, 2012). However, insomnia scores were not significantly different between the two groups in our study. One explanation may be that sleep-deprived individuals cannot identify increased sleepiness when the sleep drive is mild or moderate, or their perception of sleepiness can be masked by physical and mental conditions of high motivation, excitement, and competing needs (Hossain et al., 2005). Nevertheless, fatigue can be considered a manifestation of insufficient sleep even in the absence of sleepiness (Hossain et al., 2005; Lichstein et al., 1997).
The difference of fatigue scores between the two groups was not due to the differences of age and symptom duration, because fatigue severity was not affected by age or symptom duration and the fatigue score was not related to age. Pollak also reported that fatigue score was inversely related to age, and was not dependent on gender and symptom duration in BPPV (Pollak and Stryjer, 2015). Meng, et al. reported that the relationship between age and fatigue prevalence appeared to be “J-shaped” among both men and women, with the lowest fatigue prevalence occurring in the 60 to 64 year age group for men and the 65 to 69 year age group for women (Meng et al., 2010).
Several possible mechanisms may explain the co-occurrence of dizziness and fatigue in some individuals. Because postural control requires attentional cognitive processing (Horak, 2006), fatigue impacts mental functions such as attentional cognitive processing and results in disturbed postural control (Lundin-Olsson et al., 1998). Another explanation is that the sense of floating, neck pain, and dizziness while rotating the neck may implicate disruption of cervical proprioceptive input leading to disturbed postural control (Karlberg et al., 1996).
The DHI score showed no significant difference between the two groups. This could be explained by several factors. Although the DHI has been demonstrated to accurately discriminate between participants with and without a disability (Tamber et al., 2009), it does not specifically assess intensity and type of dizziness and the presence of neurovegetative symptoms (Tufarelli et al., 2007). Furthermore, it does not accurately reflect the presence or severity of underlying vestibular deficits (Yip and Strupp, 2018). Age, the presence of central vestibular system abnormalities, and the nature of the patient’s principal presenting symptoms have no effect on the DHI (Pollak et al., 2003).
Both groups had more than mild anxiety. The anxiety level was higher in the AUD group than in the BPPV group. It is known that many patients with organic vertigo report a sense of fear and anxiety during the vertigo attacks (Pollak et al., 2003). Dysfunction of the vestibular system can trigger a psychiatric disturbance even in a previously mentally healthy person, especially in predisposed individuals (Pollak et al., 2003). This notion is supported by anatomic and functional connections between the vestibular system and the limbic system being involved in the processing of emotional responses (Rajagopalan et al., 2017). A possible reason for the higher level of anxiety in the AUD group relates to the association of patients’ self-control against vertigo with the occurrence of anxiety (Yuan et al., 2015). BPPV patients can control the severity and even avert the attack of vertigo by avoiding quick head shaking. Therefore, the anxiety level in patients with BPPV may be lower than that of their counterpart. For the patients in the AUD group, dizziness is unpredictable and uncontrollable, which may result in higher anxiety. We speculate that the anxiety in the AUP group was not the cause but rather the result of dizziness, because in this study, patients with a past history of anxiety were excluded and the included patients were thoroughly evaluated against relevant diagnostic criteria to determine whether they had a preexisting anxiety disorder.
The patients in the AUD group may have manifested the first emergence of vestibular migraine even though they did not have migraine headache in their life. The most common causes of dizziness in adult populations are vestibular migraine, underlying anxiety, or psychogenic disorders (McFeely and Bojrab, 2008; Staab et al., 2004). Among patients older than 65 years, disequilibrium of aging is the major cause of dizziness (Belal and Glorig, 1986; Drachman and Hart, 1972), and among adolescents, vestibular migraine is the most common cause of dizziness (Lanzi et al., 1994). No matter whether the cause of dizziness is fatigue or vestibular migraine, relieving fatigue would benefit the patients.
Our study is limited by the relative short follow-up period, the absence of sleep duration data, and the lack of analysis of the clinical characteristics of the AUD group (which was beyond the scope of this study). Further study with longer follow-up period is needed to assess whether patients with a new episode of daily dizziness would eventually be found to have vestibular migraine. Also, further study factoring in patients' sleep duration would identify whether insomnia contributes to the pathophysiology of dizziness in fatigued individuals. Finally, statistical analysis of the clinical characteristics of the AUD group could identify potential diagnostic criteria of fatigue related dizziness as a defined clinical entity.
Conclusion
We believe that fatigue should be considered a cause of dizziness, given that the patients in the AUD group had a higher level of fatigue than those in the BPPV group, they had no other demonstrated cause of dizziness on thorough investigation, they were previously healthy, they had no prior history of dizziness, and dizziness decreased after fatigue was relieved. These findings lead us to propose the fatigue related dizziness experienced by these patients as a distinct clinical entity.
Acknowledgement
“This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2018R1A6A1A03025109)”.
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