Abstract
The main aim was to study the occurrence of neck- and headache in farmers exposed to seasonal tractor work which involves prolonged, continuous neck rotation. As an integral part of the Vågå study of headache epidemiology, 109 farmers were interviewed according to a set scheme in a ‘semistructured’ interview, concerning complaints in the wake of tractor work. No appreciable headache/neck-ache was found in 13 farmers; neck-ache alone was present in 66 farmers; headache/neck-ache was present in 15 farmers. For the remaining 15, the information was inadequate. Headache appeared only in connection with neck-ache. Only in those with headache did there seem to be a prevalence of nuchal features (such as reduced range of motion in the neck and positive skin-roll test). In 45% of cases, there was a carry-over effect after the chores, mostly of 1-3 days duration. Head- and neck-pain seem to be frequent in tractor drivers during chores.
Keywords
Introduction
The Vågå study of headache epidemiology mainly addresses the major headaches. However, some well-defined headaches of less importance, such as the ultrashort headache attacks, like jabs (1), have also been dealt with.
The situation of the tractor drivers was not an actual topic in the Vågå study. In the course of the first part of the study, however, one farmer after another told about their experience with tractor work. In this part of the world, farmers spend hours daily on the tractor for a few weeks during spring/autumn chores, with their neck turned. During the rest of the year, there is generally no such long-lasting, routine exposure.
At a certain point during the study (June 1996, parishioner no. 695), it was therefore decided to add a more thorough investigation of these farmers. This particular study can therefore be characterized as a spin-off effect of the Vågå study. It is accordingly not a regular prevalence study.
Materials and methods
The Vågå study was carried out in a parish in the mountainous part of southern Norway (2). The number of parishioners was 3907 just prior to the initiation of the study, which took place during a 2-year period, starting in the late fall of 1995 (Table 1). Of the accessible individuals in the age group 18–65 years, 88.6% were personally examined by the principal investigator (O.S.), according to a set questionnaire (2). The examination can probably best be characterized as a ‘semistructured’ interview (2).
Demographic data
∗88.6% of the target group.
†Parishioners from the later part of the study period who defined themselves as farmers, see Materials and methods.
It is open to question how to define a farmer in this part of the world today, since farmers at many small/medium-sized farms are only part-time farmers. In the present context, only individuals who specified farming as their main occupation were included: those who were the owners of at least a middle-sized farm, and had been doing regular farm work for at least a decade. Only the farmer himself has been given the designation of farmer (not the wife, who was termed farmer's wife). There were three female farmers, and they were included. Young males on the farms—aides, substitutes, and young family members—were not included if they had had only limited exposure to tractor work.
Excluded were also those with chronic, major neck problems (e.g. accidents involving the neck directly) and severe cervicobrachialgia, impeding the assessment of the role of tractor driving per se. The farmers were not selected in any other way. Due to the ‘gradual’ start of the study, most farmers from the early part of the study were not included. The present study should accordingly not be regarded as a regular prevalence study. However, it does provide information about the frequency of complaints among farmers interviewed according to the above mentioned principles. Not all the farmers answered all questions.
The usual duration of the period of exposure to tractor work was 1–2 weeks or even more during spring plowing/sowing and autumn harvesting periods. The head and neck were turned continuously—mostly to the right—for prolonged periods during these spells of work, and the farmers generally worked long hours.
A full examination of the head and neck, including the cranial nerves, was carried out. A long-version neurological status was included only when deemed necessary.
Various nuchal features/phenomena were particularly searched for, such as: tenderness of the upper trapezius and sternocleidomastoid muscles; tenderness over the splenius muscle; tenderness over the greater and minor occipital nerves and the tendon insertions in the back of the head; tenderness over the facet joints. Attempts at pain provocation were also made, i.e. pain irradiating to the head (and similar to the spontaneous one) through external pressure to the above mentioned, specified, pressure-sensitive points in the neck. The positive response to pressure was graded, anterior head pain exceeding a couple minutes' duration being the highest level of response. Furthermore, the range of motion in the neck was assessed clinically in a rough way (movement restriction in steps of 5°).
The skin-roll test was carried out in a standardized way along the upper border of the trapezius muscle (3), using the skin callipers (Servier, Leiden, The Netherlands), enabling estimation of both tenderness and skin thickness (4). These measurements were compared with those in a sex-matched (two females and 68 males) and age-matched control group, selected among consecutive non-farmers in the Vågå study. The above mentioned single findings on examination of the neck were summarized, and a numerical assessment of the extent of involvement could in this way be obtained (scale from 0 to 5+, with single steps of 0.5+). The mean value for these features indicating cervical abnormalities in the entire Vågå material was 0.78+. The details of this grading system will be described elsewhere.
Results
A total of 109 farmers were asked about their experience with tractor work. Fifteen of them failed to give adequate information. Of the remaining 94, 66 had had neck-ache, whilst 15 had had head- and neck-ache. Thirteen (Table 2) claimed to have no appreciable head- or neck-ache in connection with tractor work. Once started, the pain tended to continue during that day. No one admitted to transitory discontinuation of work due to these complaints.
Presence of neck- and headache
∗Four in this group had only minimal/mild neck-ache. Males/females in the total group: 106/3.
Thus, of those asked, 14%, and of those with adequate information 16%, complained of headache. The number of headache cases corresponded to 0.8% of the studied population. As already emphasized, the latter figure is clearly a minimum figure and cannot be used as a prevalence estimate.
Age of onset
The mean age of onset was around 36 years when based upon figures obtained from those who gave rather precise information. In eight cases, information like ‘10–15 years ago’, ‘approximately 15 years ago’, ‘later years’ was given. Even when trying to stipulate the mean age of onset also for these cases, e.g. using 12.5 years for ‘10–15 years’, the total mean was still approximately 36 years.
This figure should be evaluated with various reservations. Some of the youngest ones at the farm, for instance the non-included aides, might of course also have had complaints. The mean age is therefore in all probability artificially increased.
Headache characteristics
There was no case of headache without a coexisting neck-ache. Many farmers stated that only when the neck-ache reached its maximum did the headache appear. The headache seemed to be only occipital in most cases, occasionally spreading up against the vertex or anteriorly. It was almost invariably bilateral. In one case only, a right-sided predominance seemed to be present. The headache was apparently mild to moderate in intensity. Dizziness and a feeling of not being well might occasionally occur. Nausea and anorexia were not reported. We may not have been persistent enough in trying to extract the latter types of symptoms. The same may go for a throbbing quality of headache, phono- and photophobia, none of which was specifically mentioned.
The neck-ache
Neck-ache was present in 66 farmers (73%) (Table 2). The neck-ache was usually bilateral; there appeared to be a predominantly right-sided neck-ache in two cases. Neck-ache was not infrequently combined with ache between the shoulder-blades (n = 7) or in the shoulders (n = 5).
It is our impression that usually the ache was ‘moderate’, perhaps at times bordering on ‘strong’ or ‘intense’. The ache seemed to be only minimal to mild in four cases (Table 2).
The ache was accompanied by a feeling of stiffness in the neck. Whether reduced range of motion was a part of the picture in the acute stage can not be established from the present investigation, which generally was performed out of season.
Symptoms: dependency on duration of the chore
Most farmers felt that the complaints were worst at the beginning of a chore (Table 3). A kind of habituation seemed to take place during the chore in some cases. The opposite trend seemed to occur in others—with a later maximum.
Influence of duration of chore
Carry-over effect
In most cases, the headache/neck-pain was gone by the next morning, or even during the late evening on the day of exposure. It could continue like that until the end of a chore. In a number of cases, however, there was a carry-over effect of varying duration. This carry-over effect not infrequently seemed to increase as a function of the duration of the chore, with an increasing degree of morning pain. In 35 cases (45%), there was a carry-over effect at the end of the chore (detailed in Table 4). Mostly, after a couple days, tractor drivers seemed to have recuperated.
Carry-over effect at the end of the chore. Head- and/or neck-pain
In one exceptional case, the carry-over effect lasted approx. 3 weeks. Cervical abnormalities were present on examination of this farmer, but he was not so markedly afflicted subjectively as to make him ineligible for the study. One farmer claimed that there was a carry-over effect of the neck symptoms, but not of the head symptoms.
Influence of age
With continued tractor work year after year, was there any deterioration with time? Only 27 farmers responded to this question, and 17 (63% of them) had noted a deterioration over the years.
Does head/neck-ache particularly appear in farmers stigmatized from a nuchal point of view?
Features indicating cervical abnormalities were particularly searched for (see Materials and methods).
The categories 0 and 0.5+ have been combined. This may be a correct way of comparing data in this context, since even 0.5+ hardly indicates findings of putative pathological significance. In the group of < 1+(0–0.5+) factor, the percentages in the neck-ache and control groups were rather similar, i.e. 74% vs. 78%, respectively (Table 5).
Features indicating ‘abnormalities in the neck’∗ in tractor drivers' head- and neck-ache
∗See Materials and methods for further explanation. Mean age farmers: 48.0 years (range 23–67 years). Mean age controls: 48.2 years (range 31–64 years). Mean age in the whole Vågå study group: 35.9 years. The average number of factors in the headache/neck-ache group, 1.63, is significantly higher than that in controls—0.45 (P < 0.0001, Mann–Whitney U-test).
Could the subgroup with headache complaints be different? In this group, the average number of features was clearly higher than in the control group (P < 0.0001, Mann–Whitney U-test, Table 5). There is also a clear discrepancy between the number of ≥ 2-values among controls and farmers with the head/neck-ache (Table 5): farmers with additional headache from tractor work seemed to have more neck involvement than controls in between chores. It should be appreciated that the grading scale used here is a rather rough one. It is also difficult to know which feature(s) to emphasize when calculating ‘features indicating abnormalities in the neck’. Should, for example, tenderness of the upper trapezius be given the same weight as reduced range of motion in the neck? At any rate, even this rough, unsophisticated assessment system to some extent seems to discriminate between these groups.
Countermeasures
Some farmers had little discomfort (see Table 2), and some had abated their situation over the years by applying certain prophylactic measures. One had got accustomed to using a mirror (and did not have to turn the neck); two turned the whole body (and not only the neck). Four farmers implemented frequent breaks or had only short spells/shifts of work. One claimed that he did not tolerate tractor work in excess of 1 week and tried to limit his own contribution to that. One felt that a cushion filled with air on the seat helped a lot.
Discussion
Farmers in Norway are exposed to a rather interesting, ‘experimental’ situation. For weeks, in the spring and fall, years on end, they twist the neck, mostly to the right side, during tractor work. In between chores there are long periods of much less, or almost no, exposure to tractor work. This is an experiment of nature, or rather of culture, so to speak, and it would be non-practicable and unethical to imitate this situation in the laboratory or in a randomized controlled trial. The farmers can actually be their own controls, with a multitude of ‘control periods’.
The main features
The main features of the tractor drivers' neck- and headache seem to be the following.
The complaints repetitively appear in connection with tractor driving. The symptoms more often than not seem to be most marked during the first days of tractor driving. In 45% of cases, there was a carry-over effect at the end of the chore, mostly of relatively short duration: 1–2 days.
The headache seems to be of mild/moderate severity; the neck-ache may seem to be somewhat stronger. When the neck-ache reaches a culmination, a headache may be added. Headache does not seem to exist without a neck-ache. The pain in both areas is generally bilateral, as it seems to be in neck sprain. The headache mainly involves the occipital area; it may eventually spread up to the vertex and, exceptionally, further forward. The picture except for the pain/stiffness in the neck seems to be symptom-poor. Most farmers suspect that the condition might have worsened during life.
Features indicating neck-related abnormalities seemed to be more frequent and marked in those who in addition to the neck-ache also had headache than among controls (Table 5).
The marked prevalence of the male sex as well as the relatively high age of onset may be factitious, in that they are largely probably due to the special selection process of the material (see Materials and methods).
Predisposition, and consequences for health
Could those who get neck-ache of this type have a predisposition for it? This is highly unlikely, for the following reasons. All except 13 of the 94 with adequate information had experienced neck-ache, i.e. 86% of the cases (Table 2). Tractor work, and not a particular predisposition, in all likelihood underlies this discomfort. Other evidence pointing in the same direction is that the complaints in almost all cases fade away rather quickly as soon as the chore is over, leaving no particular traces, subjectively.
Headache appeared only in 16% of cases and was associated with objective findings in the neck. In those that acquire headache, there may thus conceivably be a predisposition. However, tractor work is a decisive provoking factor, since also this special complaint disappears on discontinuation of the work. Although the complaints in many farmers seemed to increase with time, in no one did it seem to have reached a chronic stage so far.
What is the influence of this neck-ache and headache on well-being? In most cases the discomfort is probably moderate: the farmers take it as something they have to live with, as part of their life. They know the cause themselves, and to the best of our knowledge no one had consulted their physician about it. Drug consumption was not systematically asked about. No one spontaneously reported drug use. Mild analgesics use was probably at a low/almost negligible level, just as in other pain conditions involving the head and neck in this part of the world.
Consequences for the understanding of cervicogenic headache
What does this information add to the story of cervicogenic headache (CEH)? There is no direct stimulus to the head during exposure to tractor work. The rotation of the neck seemed to be the most likely cause, and nuchal/occipital structures, through stretching or compression, or both, probably cause most of the discomfort. The two main components of the presently described picture, neck-ache and headache, accordingly probably both derive from the neck. This study tends to strengthen the view that headache may arise from the neck/occipital area. A further supporting observation is that headache only appeared when the neck-ache became severe. In a few parishioners, lack of neck rotation during tractor driving counteracted head- and neck-ache almost completely.
This headache, in contrast to CEH, in general tends to be in the posterior parts of the head and rarely spreads to the front. The observation that it tends to appear at a younger age than CEH in general (approx. 36 vs. 45.2 ± 13.7 years (5)) may be due to a difference in the type of pain generators.
A contributing factor may be the vibration (‘bumping’) conveyed to the driver because of the lack of an adequate shock-absorbing system on the tractors.
We had not read or heard about this type of complaint at the time we came across it in early/mid 1996 in connection with the Vågå study. It is not mentioned by the IASP (6) or IHS (7). A recent search through the literature has brought to light a couple of recent reports (8, 9). They are based on questionnaire examinations and concern health risks in young farmers (8) and headache and neck-pain in farmers in general (9). Among the activities leading to increase in neck-pain and headache, ‘driving a tractor’ was the major one (no. of participants=179 (9)). No details concerning the head- and neck-pain were given.
Tractor drivers' neck- and head-pain: future perspectives
In recent years, more farmers have started using tractors with mirrors (and consequently they do not have to rotate the head) and with shock-absorbers (to counteract the vibration). Presumably within a few years all tractors will have such equipment. It may therefore not be possible to carry out similar studies in future in Norway.
Footnotes
Acknowledgements
We are indebted to GlaxoSmithKline of Norway for generous support in all phases of the investigation. The authors are also grateful to the personnel at the Vågå Health Centre at Vågåmo for their aid. Last, but not least, we thank the inhabitants of the Vågå commune for their collaboration.