Does Lake Louise questionnaire interpret high-altitude headache as acute mountain sickness? Experience in the western Himalayas

High-altitude headache (HAH) often occurs in individuals who ascend above 2,500 m for work or recreation12. It is defined by the International Classification of Headache Disorders (ICHD-3) as mild to moderate, bilateral headache or aggravated by exertion with a temporal relation to a recent ascent above 2,500 m and easily resolves by paracetamol/ibuprofen/within 24 h of descent to below 2,500 m³. So far, there are no formal questionnaires or techniques used for diagnosing HAH other than fulfilment of these criteria. HAH has become a health issue that needs a viable solution for the productivity of individuals inducting to HA for recreational and professional reasons.

Acute mountain sickness (AMS), on the other hand, can be diagnosed using questionnaires like the Lake Louise Questionnaire (LLQ)456. The 2018 revised LLQ is a research-oriented questionnaire filled personally or with the help of a researcher and defines AMS as a syndrome of symptoms in an individual with a history of a recent ascent beyond 2,500 m, with a four-point severity scoring (0 to 3) for each symptom, with at least one point for headache wherein AMS is diagnosed with a total of three points or more7.

Thus, the definitions of HAH and AMS state that both occur in individuals who ascend to high altitudes and can be reduced by ibuprofen38. There are also differences between HAH and AMS as summarized in Table I3791011121314151617.

There are several studies which claim HAH as a headache seen in high altitude. Several studies have reported AMS as HAH with other symptoms such as gastrointestinal symptoms, dizziness or fatigue11141819. In certain studies which were conducted on prophylaxis for headaches at high altitudes, distinctions were made in efficacy of drugs to reduce HAH and AMS920. Therefore, there is a need to deliberate on whether HAH is an independent entity or a part of AMS.

This lack of clarity in ascertaining HAH and AMS makes them prone to overreport one another and thereby hindering studies pertaining to diseases of high altitude. This pilot study was undertaken to determine headaches that occur in lowlanders on acute ascent to high altitude in western Himalayas that can be defined solely as HAH or AMS and those that can be defined as HAH as well as AMS.

Material & Methods

Study population: Participants of this pilot study are healthy Indian male lowlanders of 18 to 45 yr including both fresh (first timers) and re-inductees who ascended to Leh city (3,500 m) by air to acclimatize before further ascent. These participants were ruled out of being known cases of migraine/ headache or any other confounding factors. The study was approved by the Institutional Ethics Committee of Armed Forces Medical College, Pune. A written informed consent was taken from all the participants before the start of the study.

Study protocol: The participants arrived at 3,500 m by air before noon and interviewed only during the evenings to rule out any travel-related headache. The subsequent five days, participants were interviewed for identifying new cases or to observe any further changes in headache. Once any participant complained of a headache, detailed history, including water intake and sleep detail was obtained along with relevant clinical examination and ibuprofen (400 mg twice a day) was given as part of the treatment to avoid any bias due to other medication for headache.

Studies have shown that a Visual Analogue Score (VAS), self-assessed by marking on a 10 cm line on a scale of zero as no headache to 10 as severe, describes the intensity of headache more accurately than the four-point system used by LLQ21. VAS score for mild-to-moderate headache was <5 and was used for defining the patients of HAH.

All participants with headache were assessed for HAH and AMS based on fulfilment of criteria for HAH by ICHD-3 and LLQ, respectively.

The clinical parameters were measured by using multipara monitor (Truscope, Schiller, Switzerland) measured after 30 min of rest, in the supine position. Data were analyzed on the SPSS 20 software (IBM, Armonk, NY, USA).

Results & Discussion

A total of 1228 participants were observed for headache. Table II shows their baseline parameters and Figure 1 depicts the distribution of headache cases.

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Fig. 1

Distribution of headache cases analyzed. HAH, high altitude headache; AMS, acute mountain sickness.

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Table III shows HAH and AMS in total participants, fresh and re-inductees. The incidence of headache in this study was low at 6.4 per cent as compared to the 25-60 per cent shown in other studies2223 which can be attributed to the difference in altitude where the studies were conducted, number of re-inductees, a complete bed rest after arrival and advice to take tablet of ibuprofen for those having a headache.

Figure 2 shows that participants with headache on the first day exhibited both bilateral and unilateral types of headache. Out of the 51 who experienced headache on the first day, 24 (43.1%) cases were HAH only, 14 (31.3%) cases were defined as both HAH and AMS and 13 (25.5%) cases were AMS only. The cases defined only as HAH showed predilection to bilateral headaches (20 out of 24 participants), which was not seen in AMS-only individuals. All 14 HAH and AMS overlap cases showed only bilateral headache, which points toward the possibility of HAH cases being added erroneously as AMS.

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Fig. 2

Character of headache on first day.

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A one-way ANOVA revealed that there was no significant difference other than in the heart rate [F(2,51) = (4.756), P =0.013] among clinical parameters between individuals defined as AMS, HAH or both.

The correlation of parameters within a group were significantly different. In HAH cases, there was a significant negative correlation between systolic blood pressure (BP) and sleep (PC: -0.328, P=0.03), indicating that good quality sleep helps in reducing the initial surge in systolic BP during the period. In case of AMS cases, it was found that VAS showed a negative correlation with SpO₂ (PC:-0.437, P=0.023) as well as with water intake (PC:-0.474, P=0.02). It emphasizes that headache accompanying AMS can be reduced significantly if water intake and SpO₂ is increased which can be incorporated in treating AMS cases. Further studies, however, are needed for more clarity on this aspect. In cases where both AMS and HAH could be defined, the correlation of VAS and SpO₂ was significantly reversed (PC: 0.744, P=0.01), demonstrating a departure from other cases of AMS.

Therefore, this study points to the fact that LLQ includes a few cases of HAH, which was apparent when the two definitions were used on the same individual. This kind of difference in cases was discussed in another study by Silber et al24 although their conclusion was to include the LLQ criteria of AMS in ICHD-3 to define HAH. Further analysis of our study showed that cases defined by both have the relation of SpO₂ and VAS in reverse when compared to other AMS cases, indicating a difference in pathophysiology. Pathophysiology of AMS is considered the milder end of the spectrum with much more severe diseases such as high-altitude cerebral oedema, while HAH is considered innocuous and resolves by itself. This distinction, if made properly and HAH cases removed from AMS, can help one understand the underlying mechanism of high-altitude illnesses better.

There was a subset of participants with a bimodal appearance of headache, first occurring within the first 24 h and a second episode between the second and the third days describing a headache akin to AMS, showing another pathophysiology at play for causing AMS. This study thus follows the observation of the study by Berger et al17 where three types of AMS pathophysiology were proposed.

The fresh inductees in the present study showed a higher incidence for both HAH (7.37%) and AMS (10.53%) as compared to HAH (1.8%) and AMS (2.55%), in re-inductees, a reduction to 25 per cent as compared to fresh inductees (Odds Ratio (OR): 4.5, P <0.001) to have AMS as demonstrated in several other studies2526. The same was also noticed for HAH (OR: 4.33, P<0.001). However, the duration and severity of headache did not show any significant difference once AMS set in neither in fresh nor re-inductees. This points to a possible physiological mechanism where participants preserve the effects of acclimatizing in high altitude, which is then protecting the body on subsequent exposures.

This study only considered headache as a symptom which is deemed necessary to diagnose AMS. However, there is a chance of bias when it comes to correlation with other symptoms, which could be removed by using a different questionnaire that considers headache independently. This study has not considered the changes in the clinical parameters of others who did not have headache or other symptoms during acclimatization and needs further validation.

HAH, which is known to have a temporal relation to ascent to high altitudes, is a distinct entity to headache that appears in AMS because of the difference as per the definition. The phrase ‘AMS is HAH with other symptoms’ needs to be revised. LLQ while diagnosing AMS, tends to overestimate its numbers by including some of the HAH cases. Re-inductees receive significant protection from high altitude illnesses on ascent and needs further research. There is some relevance on the dictum of having good sleep and hydration to reduce the incidence of high-altitude illnesses. Further research on a larger heterogeneous and diverse population involving both AMS and HAH during gradual and rapid ascents with follow up to higher altitudes is suggested.