Although the definition of motion sickness has been expanded to include stimuli beyond pure vestibular stimulation, in the present study motion sickness was induced by a complex vestibular stimulation in darkness.
We acknowledge that our definition of normal/abnormal sickness absence is based solely on the subjective opinions of the authors.
However, less well known are the other conditions, chiefly neurological, that may arise completely outside the usual definition of altitude sickness [ 3].
16 Where studies did not use the Lake Louise scoring system, we chose the primary end point to be the absence of acute mountain sickness, defined using a validated symptom scoring system such as the general high altitude questionnaire, the acute mountain sickness-cerebral score, or a clear definition of acute mountain sickness predetermined by the original study authors.
Because medicine is an empirical science without a theoretical basis (bio-molecular foundations cannot replace a theory of medicine), uniform definitions of health, sickness and the value of health services are lacking.
After we had accessed the full text and reviewed the data, we excluded studies if a clear definition of acute mountain sickness was not stated or if the incidence of acute mountain sickness was unclear among the study population.
There is no generally established definition of long-term sickness absence in the literature, and number of days, regarded as long-term sickness absence, vary considerably between different studies i.e. from >3 days to 90 days or more [ 6, 7].
Owing to the scope of the literature analysed, the studies included in the meta-analysis did not share a standard definition of acute mountain sickness to enable the incidence to be determined among participants.
After 12 weeks, the national insurance scheme requires an extended plan and meetings towards the same purpose, which falls close to the previously used definition of long-term sickness absence of 90 consecutive days [ 42].
The exploration of the philosophical complexity that lies between sickness and health is perhaps the most urgent matter facing medicine and literature, because scientific definitions of illness often run up against humanist definitions of identity.
