The study revealed five factors that were significantly associated with neck and shoulder pain. General health showed the highest association with the risk of experiencing neck and shoulder pain. Participants with moderate or poor health were more than twice as likely (ORs: 2.3 and 2.8, respectively) as healthy individuals to experience neck and shoulder pain. Participants with sleep disturbances had an OR of 1.7 for neck and shoulder pain. We observed weak associations between neck and shoulder pain and poor job satisfaction (ORs: 1.2 to 1.3) and sitting for less than 7 h per day (OR: 1.1). Our results also showed that aerobic physical activity was negatively associated with neck and shoulder pain. Participants who performed aerobic exercise for more than 60 min per week, at a level that enhanced heart rate and breathing, were less likely to experience neck and shoulder pain (OR: 0.8) than participants who did not perform aerobic exercise. In this study, we distinguished between aerobic physical activity (physical activity that is planned, structured, and repetitive, which improves or maintains physical fitness) and general physical activity (any bodily movement generated by skeletal muscles that results in energy expenditure) . For example, general physical activities included walking, cycling, or gardening.
Moderate or poor health showed the highest association with neck and shoulder pain. One of the most important ways to improve health in adults is to maintain active habits and to perform moderate physical activity for a minimum of 150 min per week and/or vigorous physical activity for 75 min per week. Moreover, additional health benefits can be gained with up to 5 h/week of moderate physical activity and 2.5 h/week of vigorous physical activity . It is well known that physical activity and sedentary behaviour are associated with neck pain and poor health [11, 19, 23, 29]. However, there seem to be large variations in the combination of these variables among individuals . Several health conditions have been shown to benefit from physical activity, for example, coronary heart disease, cancer, diabetes, and sleep disturbances . However, in the current study, we found no significant association between > 150 min/week of general physical activity and risk of neck and shoulder pain. Overall, our participants reported low levels of general physical activity. Most participants performed general physical activities for less than 150 min/week (64% of participants with neck and shoulder pain and 63% of participants without pain). Office workers who reported walking as their general physical activity had a reduced incidence of neck pain onset, but there was no significant difference in neck pain intensity, compared to the control group . In the present study, we found an association between aerobic physical activity, i.e., exercises that enhance breathing and heart rate, and lower odds of experiencing neck or shoulder pain. We found no association between physical activity (e.g., walking) and the risk of experiencing neck or shoulder pain. However, in the present study, we could not determine causal relationships; for example, a higher intensity of physical activity might have reduced pain in the upper body, or conversely, individuals with no neck pain may have been more likely to participate in moderate to vigorous exercise.
Despite the low levels of general physical activity in the current study, 85% of participants with no neck and shoulder pain reported good to very good health, compared to 64% of participants with neck and shoulder pain. However, the risk of developing a chronic condition, such as musculoskeletal disorders or pain, coronary heart disease, cancer, diabetes, or premature mortality, was likely to be considerable for many individuals, due to their low physical activity levels.
In contrast, more than 60 min/week of aerobic physical activity was associated with a reduced risk of neck and shoulder pain. Indeed, more than 60 min/week of aerobic exercise was reported by 49% of participants with no neck and shoulder pain, compared to 39% of individuals with neck and shoulder pain. In a previous study, physical activity for 5 h/week or more was associated with a lower risk of neck pain , but the intensity level was not explicitly explained in that study. Nevertheless, the authors showed that, for pain in the upper body, low-intensity physical activity (e.g., walking) may be insufficient to reduce pain intensity, when the activity is performed for less than 5 h/week . Alternatively, as indicated in the present study, moderate aerobic physical activity might affect pain intensity. Currently, the available evidence for the effect of physical activity on neck and shoulder pain remains inconclusive [12, 16, 28, 29], but moderate-to-vigorous activity may be protective and can be included in clinical recommendations.
In the present study, neck and shoulder pain were associated with sleep disturbances. Previously, Holm et al.  found that the risk of developing neck and lower back pain was higher in individuals who reported poor work ability and sleep disturbances, and Finan et al. reported similar findings . Individuals living with chronic pain experience sleep disturbances, due to the pain . Our findings in the present study are consistent with those studies.
It has previously been reported that short periods of sitting are related to a lower risk of neck and back pain . In contrast, in the present study, we found that sitting for less than 7 h per day was related to a small increase in the risk of neck and shoulder pain. However, too much activity, without rest during the day, may cause pain when the activity is static, repetitive , or related to stress . Moreover, another study showed that, among blue-collar workers, increased sitting time at work reduced the risk of neck pain . Thus, sitting and relaxation times, relative to physical demands on muscles, are likely to be highly individual.
We found that time spent working was not significantly related to neck and shoulder pain. However, we also found that neck and shoulder pain was weakly associated with poor job satisfaction.
The main study limitation is that we could not draw causal relationships, due to the cross-sectional nature of our study. Another limitation is that self-reported estimates of exercise and activity levels have been questioned. For example, individuals with cancer or fibromyalgia have over-reported their physical activity levels in self-reported questionnaires [36, 37], and objective methods have been recommended. However, it would be extremely costly, and probably not possible, to measure physical activity objectively in all the individuals in a large, population-based cohort with several thousand participants. Moreover, self-reported and objective methods produced contradictory results in a study by Neupane et al. . They found that musculoskeletal pain was significantly correlated with self-reported occupational physical activity, but not correlated with objectively measured activity levels. Therefore, other factors, apart from the fact that exercise and physical activity were self-reported, might have been associated with neck and shoulder pain. Two different questionnaires were used in the study. The questionnaire sent to individuals aged over 30 years included more questions than the one sent to individuals aged between 18 and 30 years. The reason for fewer questions being asked of the younger age group was to increase the response rate among younger adults. We do not think that this discrepancy between the questionnaires impacted the study results because the questions included in the present study were identical in both questionnaires. Another limitation relates to the question regarding neck or shoulder pain. This question had three response options: ‘No pain’, ‘Yes, mild pain’ or ‘Yes, severe pain’. There was no clear definition given to distinguish between mild and severe pain, and we did not use a validated pain measurement; all responses were based on subjective interpretations of the question and self-assessments. Individuals in the study could have experiences of pain in the neck and/or shoulders. The questionnaires included no questions about intensity, duration, or frequency of pain or a pain sketch. Thus, we could not draw any conclusions about potential associations between pain severity, pain location, and the predictive factors. However, the aim of this study was to distinguish between individuals with or without upper body pain (neck or shoulder pain) and to relate the presence/absence of this pain to potential explanatory factors. Moreover, only 14% of participants reported severe pain. Therefore, we considered it reasonable to forgo the distinction between mild and severe pain and dichotomise the responses into categories of no pain vs. pain. The question about disturbed sleep had limitations regarding information about the severity of sleeping problems. The question had only three response options: ‘No’, ‘Yes, mild sleep problems’, or ‘Yes, severe sleep problems’. However, the question was able to distinguish between individuals with and without sleep problems. We intended to select cut-off values that could distinguish between individuals who followed the current recommended physical activity level (in 2017, ≥150 min)  and/or aerobic physical activity level (≥75 min)  and individuals who practised activities below the recommended levels. Unfortunately, the response alternatives for aerobic exercise did not allow a threshold of 75 min. Therefore, we chose a 60-min cut-off, because it included all participants who followed the 75 min recommendation, and excluded most participants who did not fulfil the recommendation. To date, there is no clear recommendation regarding sitting time. Health risks and the potential impact on neck and shoulder pain that were related to sitting time appeared to be associated with exercise habits . Moreover, sitting times of > 6–8 h appeared to be related to an increased risk of disease and an enhanced risk of experiencing neck and back pain . Therefore, we chose a cut-off of 7 h. Dichotomising and trichotomising variables had some potential limitations. Firstly, they might lead to an underestimation of the extent of variation in the outcomes. Secondly, individuals close to the cut-off value were considered to be very different from individuals who were just on the opposite side of the cut-off value, but in fact, they might be very similar.
In the present study, the dichotomisation for neck pain distinguished between individuals who expressed a ‘No’ response and individuals who expressed one of two responses that indicated a ‘Yes’ response. Therefore, we could clearly distinguish between individuals with and without neck/shoulder pain, individuals with and without sleep disorders, and individuals who followed or did not follow the current recommendations for physical activity and aerobic exercise. However, for two questions, health and job satisfaction, the responses could not be easily dichotomised. The central value (moderate) could have referred to either ‘moderately good’ or ‘moderately poor’ response alternatives. Therefore, we could not readily assign the ‘moderate’ category to either ‘good’ or ‘poor’. Instead, we decided to trichotomise the responses to distinguish between good, moderate, and poor/low.
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