Cabin Location and the Likelihood of
Motion Sickness in Cruise Ship Passengers
Paul M. Gahlinger
Background: The prevalence of motion sickness approaches 100% on rough seas. Some previous studies have reported
a strong association between location on a ship and the risk of motion sickness, whereas other studies found no association. This study was undertaken to determine if there is a statistical association between the location of the passenger
cabin on a ship and the risk of motion sickness in unadapted passengers.
Method: Data were collected on 260 passengers on an expedition ship traversing the Drake Passage between South
America and Antarctica, during rough sea conditions. A standard scale was employed to record motion sickness severity.
Results: The risk of motion sickness was found to be statistically associated with age and sex. However, no association
was found with the location of the passenger cabin.
Conclusions: Previous research reporting a strong association of motion sickness and passenger location on a ship, studied passengers in the seated position. Passengers who are able to lie in a supine position are at considerably reduced
risk of motion sickness. Expedition or cruise ships that provide ready access to berths, allow passengers to avoid the
most nauseogenic positions. The location of the passenger cabin does not appear to be related to the likelihood of
seasickness.
Motion sickness has been a common malady since
the advent of vehicular travel, as evidenced by its various descriptive terms: from camel sickness and elephant
sickness to the more recent car sickness, airsickness, and
space sickness. All are synonyms for the motion-induced
nausea most familiar as sea sickness. Indeed, the word nausea is derived from the ancient Greek “naus” meaning
ship. Despite engineering advances and the increasing
sophistication of modern ships, motion sickness continues to be a problem for contemporary sea-going travelers. Surveys have shown that up to 100% of ship passengers
become seasick under rough conditions.1
After an earlier decline, ship travel has increased
tremendously in recent years with the growing popularity
of cruise ships and expedition-style voyages. These ships
go far beyond the traditional destinations and now traverse the most turbulent seas and penetrate into the
polar regions. Large, modern cruise ships feature roll
stabilizers, and other measures to reduce motion sickness.
Smaller expedition ships, especially those that are designed
for ice penetration, have a much greater roll rate. Passengers on these ships are justifiably concerned about
spending their expensive vacation in nauseated discomfort.
The cause of motion sickness is generally considered to be a mismatch of vestibular and visual sensations,2
which in turn stimulates the vomiting center within the
brain. Not all people are equally susceptible. Infants
below the age of 2 are rarely affected, after which susceptibility rapidly increases with age to a peak between
4 and 10 years, and then gradually falls.3 Over all ages,
females tend to be more susceptible than males. Recent
food ingestion, dairy products, and high sodium, high protein, or high calorie foods have also been associated with
increased susceptibility.4 Aerobic conditioning further
increases susceptibility, perhaps by increasing parasympathetic tone. Oral contraceptive use enhances susceptibility, and women are especially vulnerable during
menses or pregnancy.1
Motion sickness tends to occur with acceleration in
a direction perpendicular to the longitudinal axis of the
body, which is why head movements away from the
direction of motion are so provocative. For vertical oscillatory motion (appropriately called heave), motion sickness is most likely at a frequency of 0.2 Hz.3 This would
be experienced, for example, in a ship with a roll rate of
5 seconds. The incidence of motion sickness falls quite
rapidly with higher frequencies, perhaps accounting for
its relative absence among users of smaller water craft such
as windsurfers, jet skis, canoes or kayaks, and very small
sailboats (and the lower incidence among riders of horses
rather than camels or elephants). Adaptation to the sensory conflict occurs to a variable extent, and motion sickness tends to subside after 36–72 hours with continued
exposure. However, on return to the preexposure environment, symptoms can recur (mal de débarquement)
until readaptation takes place.3
Paul M. Gahlinger, MD, PhD, MPH: Rocky Mountain Center
for Occupational and Environmental Health, University of
Utah, Utah.
Reprint requests: Paul M. Gahlinger, MD, 88 K Street, #5, Salt
Lake City, UT 84103.
J Travel Med 2000; 7:120–124.
120
G a h l i n g e r, M o t i o n S i ck n e s s
Given these characteristics, passengers can take a
number of measures to reduce their risk of motion sickness, such as looking at a stable horizon, minimizing head
movements, and avoiding concentrated visual activity such
as reading.5 The distance from the center of a ship determines the amount of vertical acceleration experienced
by a passenger in that location, and should therefore
affect the likelihood of motion sickness. Accordingly, the
most common recommendation is to seek out a position near the center of the ship.1,6 However, this recommendation has not been consistently supported by
empirical research. For example, a recent study of 1,350
passengers on a cruise ship found no association between
seasickness and the location of the cabin.7 Earlier studies of troops on Military Sea Transport Service ships8 and
US Navy escort vessels9 also found no association between
the location of crew berths and the likelihood of motion
sickness. Furthermore, laboratory simulation of shipboard motion found that the amount of acceleration was
not a reliable predictor of motion sickness.10 Contrary
to these reports, a well-designed study employing onboard
accelerometers and interviews with 4,915 passengers on
an English Channel ferry, found a very strong association between motion sickness and passenger location on
the ship, as well as the amount of acceleration to which
the passenger was exposed.11
In view of these contradictory reports, this study was
designed to examine the association between the location of the passenger cabin on a ship, and the likelihood
of motion sickness reported by unadapted passengers.
Methods and Subjects
Subjects were passengers on two voyages of an
expedition ship, traversing the Drake Passage between
Ushuaia, Argentina, and the Antarctic Peninsula. This passage is reputed to present among the roughest of sea conditions. The traverse requires about 2 to 3 days, at an
average speed of 11 knots. On the two voyages for which
data were collected, the Drake Passage lived up to its reputation with gale force winds and sea swells up to 9 m.
All passengers arrived at the port of embarkation following airline flights from North America or Europe.
Prior to the voyage, each passenger had completed a medical history questionnaire which was reviewed by the ship’s
121
physician. Passengers were informed about sea conditions,
the likelihood of motion sickness, and offered a choice
of meclizine, dimenhydrinate, or transdermal scopolamine, along with patient education regarding the use
and side effects of these medications. The ship’s physician invited each passenger to participate in the study.
Of the combined 265 passengers on the 2 voyages, 260
(98%) agreed to participate. Subjects ranged in age from
15 to 87; 115 (44%) male and 145 (56%) female. Each
of the subjects was given a standardized questionnaire and
then interviewed at the end of the traverse. Motion sickness severity was determined by a ranked standardized
scale,12 with four levels of severity ranging from 0 (no
symptoms) to 3 (vomiting or incapacitation).
All passengers were fluent in either English or German (over half of the passengers were natives of Germany,
Switzerland, or Austria). For non-English speaking passengers, the questionnaire and interviews were conducted in German.
The ship had a length of 87 m, breadth of 12.2 m,
and gross tonnage of 3,724 rt. All passengers had cabins
with two or more portholes. The distance from the
berth in each cabin to the center of the ship, near the
shaft room, was calculated. The values for this distance
were used as the independent variable in a step-wise multiple regression model, with other variables including age,
sex, and the use of antimotion sickness medications.
The outcome variable was the degree of motion sickness.
The motion of a ship is complex. It moves in three
axes: (i) horizontally, in the direction of travel, (ii) rolling
from side to side, and (iii) vertically, as it rides up and down
a swell. It is this last type of motion that appears to be
the most nauseogenic.
Ideally, the amount of motion experienced by ship
passengers—particularly vertical motion—is quantified
by use of an accelerometer. Accelerometers were not used
in this study. However, it is possible to calculate the
approximate vertical acceleration of any location on the
ship by estimated parameters of the ship’s motion and sea
conditions. Under the assumption that the ship moves
with constant horizontal velocity, v, on a low frequency
sinusoidal wave with amplitude, A, and roll rate of T, the
velocity in the vertical direction, y, is a function of the
distance from the center of the ship, r, in a given unit of
time, t:
Equation
d
d 
1



1 
 1
  
y(r,t) = A ⋅ sin  ⋅ 2 ⋅ π ⋅ t + r ⋅ sinatanA ⋅ 2 ⋅ π ⋅
⋅ cos 
⋅ 2 ⋅ π ⋅ t   
dt
dt 
T



v ⋅T 
v ⋅T
  
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J o u r n a l o f Tr a v e l M e d i c i n e , Vo l u m e 7, N u m b e r 3
Figure 1 Cabin location and motion sickness inducing acceleration.
Motion Sickness Score
Vertical acceleration at any location may then be calculated as the derivative of this function.
Figure 1 provides these calculated values for the
ship. Distance, refers to the distance of a passenger cabin
from the center of gravity of the ship. The maximum
upwards and downwards acceleration of the cabin is
shown to clearly increase with distance from the center.
These values are given both as forces of acceleration, on
the left vertical axis, and as a percentage deviation from
earth’s gravity on the right axis. For example, the maximum upward acceleration experienced in a cabin located
40 meters from the center of the ship was 10.59 m/s2,
or about + 0.68 m/s2 beyond gravity. This can also be
described as 0.07 units of gravity (G). To put this into
perspective, a force of 1 G on the descent would be sufficient to lift a person off the floor, or give the sensation
of a free-falling elevator. On this ship, a force of 0.04 G
to 0.07 G (or 4 to 7% of a unit of gravity) may seem small
in comparison with an aircraft engaged in acrobatic
maneuvers, which can be as much as 100 times this
amount. However, on a ship, the much smaller forces are
repeated every few minutes and can produce considerable discomfort over a long period.
Results and Statistical Methods
Peak motion sickness scores of the subjects are presented in Figure 2. None of the subjects reported motion
sickness on the flight prior to the voyage, or had been
on a ship within the previous 2 months.
The age and sex distribution of subjects in this
study was typical of expedition or cruise ship passengers,
with a preponderance of middle-aged persons and a
greater proportion of females. The reported incidence
of motion sickness in this study is also characteristic of
the general population, with a higher incidence among
the younger subjects, and females reporting greater susceptibility than males. The initial zero value is anomalous;
Figure 2 Mean peak motion sickness
score.
123
Motion Sickness Score
G a h l i n g e r, M o t i o n S i ck n e s s
Figure 3 Cabin distance and motion sickness.
Distance from Ship Center (m)
it is due to just 2 cases, one of whom was ill throughout the voyage with an unrelated condition.
Sixty-nine (27%) of the study participants declined
the offered motion sickness medication. The reasons
given included one or more of the following: dislike of
medication, concern about side effects, concurrent medical conditions (benign prostatic hypertrophy, and glaucoma), denial of motion sickness susceptibility, and a
belief that motion sickness was purely psychological.
Of the 260 subjects, 94 (36%) reported no motion
sickness, 31 (12%) reported mild symptoms, 47 (18%)
reported moderate symptoms, sufficient to restrict normal activities, and 88 (34%) reported vomiting or prostration.
Statistical analysis showed a significant association of
motion sickness with age and sex, as expected, but no
association with distance of the passenger cabin from the
gravitational center of the ship (F = 0.04, p > .8, Fig. 3).
There was no statistical association between the use of
motion sickness remedies and the location of the passenger
cabin. In statistical analyses that report a lack of association, it is appropriate to do a calculation of statistical
power, to determine whether there is indeed no association, or whether the evident lack of association is simply due to excessive variability among the data, or to an
inadequate sample size. High variability, or an insufficient
number of observations, may prevent the discovery of a
statistical difference, even when a true difference is present. An iterative procedure was used to calculate statistical power for regression equations,13,14 entering the
observed standard deviation of the sample data. Under
the assumption of a level of significance (alpha) of .05,
and sample size of 260, the calculated power was .97. This
result suggests that there is a 97% certainty that no association is present between cabin location and motion sickness in this group.
Discussion
The perception persists that a central cabin location
is recommended to avoid motion sickness. This recommendation is repeated in most published travel guides,
including the current guide to Antarctica,15 as well as
informally by travel agents and physicians. It is also
reflected by the increased prices of mid-ship cabins and
the difficulty in booking these cabins.
Whereas the association of age and sex with motion
sickness was characteristic of previous studies, the lack
of an association with cabin location was less expected,
given the common recommendations and the emphasis that some passengers placed on a cabin near the center
of the ship. On this ship, as in most others, centrally
located cabins commanded a higher price partly because
of their increased desirability as a less sea sicknessinducing location.
Why was there no change in the risk of sea sickness with cabin location? A review of the physiology of
the vestibular apparatus in the inner ear may provide the
answer. The vestibular system consists of a vestibule and
three semicircular canals fixed at right angles to one
another in three orthogonal planes. Each semicircular
canal contains neuroepithelium which is stimulated by
angular acceleration around the axis of the canal. The
vestibule contains additional neuroepithelia to detect
linear acceleration: the utricle for vertical acceleration and
the saccule for horizontal acceleration.16 The posterior
and anterior (superior) semicircular canals, and the associated utricle, are considered the gravity set, because
they respond to tipping motions out of the horizontal
plane. It is the stimulation of these neuroepithelia, together
with a lack of corroborating information from the visual
and other senses, that is believed to be the cause of
124
motion sickness. The horizontal semicircular canal, and
the saccule, are believed to provide much less inducement
to motion sickness. However, stimulation of the gravity
set takes place primarily when the head of the subject is
in an upright position. When the subject is in a supine
position, the vertical canals most closely assume a horizontal position, and are relatively resistance to stimulation by vertical acceleration. Likewise, in the recumbent
position, the macular otoliths of the utricle lie beside,
rather than on, the macular cilia, and are much less
responsive to vertical acceleration.17
It may therefore be expected that ship passengers
who are able to assume a recumbent, or supine posture,
would experience some degree of protection from
motion sickness. If so, the apparent contradiction in previous reports is resolved: the surveys aboard military and
cruise ships used cabin or berth location as a reference,
while the study of passengers on the English Channel
ferry used seat location—in which the passengers had a
largely upright posture.
Conclusion
All modern cruise or expedition ships provide cabin
facilities to passengers, allowing them to lie down when
desired. This study suggests that the location of the cabin
is not related to the risk of motion sickness for passengers at liberty to use their facilities,and this concern should
not be a factor in cabin selection.
It is recommended that travel consultants explain to
passengers that the location aboard a ship is related to the
risk of sea sickness only when the passenger is seated or
standing. When lying down, the distance from the center of the ship no longer appears to affect motion sickness. Therefore, the choice of a berth or cabin should be
determined by other factors, and not a concern about
motion sickness.
Acknowledgment
The author wishes to thank Captain Karl-Ulrich
Lampe and Chief Engineer Harm Kruse, of Society
J o u r n a l o f Tr a v e l M e d i c i n e , Vo l u m e 7, N u m b e r 3
Expeditions, and Mr. Kai Kuck of the Department of Bioengineering, University of Utah, for their very helpful
advice in this study.
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