Background
A notable proportion of adults are globally regarded as physically inactive [
1]. Population-based studies have also shown that physical activity levels are lower in older age groups (60+) [
2‐
4]. This is concerning, as regular participation in physical activity helps to reduce many negative age-related changes in the human body, such as the decline in muscle strength, bone density and cardiovascular fitness [
5]. In women, menopause is associated with worsening of physical performance [
6,
7] and decline in physical activity levels [
8]. Regular physical activity could help to prevent negative menopausal-related changes, such as muscle strength and power loss and increased visceral adiposity [
7,
8].
To promote physically active lifestyle, it is crucial to identify the factors associated with physical activity and inactivity in different stages of life. Among the potential psychological factors, pervasive individual differences in feeling, thinking and behaving, called personality [
9], may underlie an individual’s willingness to be physically active and help identify risk groups for inactivity.
Individual differences in personality traits are known to be relatively stable throughout the adult lifespan [
10]. However, some longitudinal studies indicate that extraversion declines with age, whereas neuroticism typically declines from early to middle-adulthood and may slightly increase thereafter [
11]. Personality traits may shape a multitude of health behaviors, including physical activity [
12‐
14]. Previous meta-analyses have shown that adults scoring high on extraversion (i.e., a tendency to be outgoing, sociable, active, and assertive) and low on neuroticism (i.e., the tendency to experience negative emotions, such as anxiety, tension and self-pity) report higher levels of physical activity [
12‐
14].
Most previous studies have used self-reported measures of physical activity. Correlations between self-reported and device-based physical activity measures have been low to moderate [
15,
16], indicating that they measure partly different aspects of physical activity. Thus, including device-based physical activity measures may yield new knowledge in research on personality and physical activity. The strengths of device-based physical activity measures, such as accelerometers, include minute-by-minute monitoring, also of light intensity physical activity that is often underreported in questionnaires [
17]. This is important, especially among older adults whose daily activity is mainly light intensity [
17]. Accelerometer studies have not reported consistent associations with personality traits [
18‐
22]. This may be due to relatively small sample sizes and the use of convenience samples of active older adults (
n = 69) [
20], obese middle-aged men and women (
n = 235) [
18], college women (
n = 294) [
19] and young men and women (
n = 64) [
22].
However, hip-worn accelerometers have their limitations. For example, hip-worn devices imperfectly capture cycling or upper-body exercises [
17,
23]. In addition, the thresholds for different intensities of physical activity (light, moderate, vigorous) do not take individuals’ fitness levels into account [
17,
24]: accelerometer-measured light activity, for example, may be experienced as very strenuous by low-fit individuals. It is, therefore, important to measure physical activity in multiple ways. Moreover, although accelerometers and questionnaires do not measure exactly the same aspect of physical activity, personality may play a role in how people estimate and report their physical activity. Individuals high in extraversion may over-report and individuals high in neuroticism under-report their physical activity levels. It has been found, for example, that individuals who scored high in neuroticism were more likely to over-estimate their weight, whereas those higher in extraversion typically assessed themselves as leaner and taller than they actually are [
25]. To our knowledge, the associations of both accelerometer-measured and self-reported physical activity with personality traits have simultaneously been investigated in only one previous study, which found that, among college women, extraversion was associated only with higher self-reported physical activity whereas neuroticism was associated only with lower moderate-to-vigorous accelerometer-measured physical activity [
19].
This study aimed to contribute to this growing area of research by exploring a) the cross-sectional associations of extraversion and neuroticism with both accelerometer-measured and self-reported physical activity and b) the role of extraversion and neuroticism in discrepancies between accelerometer-measured and self-reported physical activity. This study is based on two relatively large samples of Finnish adults, which represent two groups at risk for physical inactivity: menopausal women and sedentary or at most moderately physically active older adults.
Discussion
This study investigated whether extraversion and neuroticism are associated with accelerometer-measured and self-reported physical activity among two samples of Finnish adults: a sample of middle-aged women and a sample of older women and men. Among the middle-aged women, those who scored higher in extraversion and lower in neuroticism, reported higher levels of physical activity. Among these women, lower scores in neuroticism also had a weak negative association with accelerometer-measured leisure time MVPA. Neither of these associations were observed among the older adults. Among older adults, high neuroticism was associated with underreporting physical activity compared to accelerometer-assessed physical activity.
In line with the literature [
12‐
14], extraversion had a positive association with self-reported physical activity among middle-aged women. Furthermore, as in previous studies among college women [
19], obese middle-aged adults [
18] and older adults [
21], extraversion was not associated with accelerometer-measured physical activity. It is possible that people high in extraversion tend to give socially desirable responses to self-reports [
19]. However, extraversion did not explain the discrepancy between self-reported and accelerometer-measured leisure time physical activity and a showed a tendency towards an association with accelerometer-measured leisure time MVPA (
p = .076). However, extraversion seems to be related to leisure time exercise alone and not to light-intensity daily activities.
In line with previous studies [
12‐
14], in the sample of middle-aged women, neuroticism was negatively associated with self-reported physical activity. As in the study among college women [
19], this negative association was also seen with leisure-time accelerometer-measured MVPA. Although the association with accelerometer-measured MVPA was weak and would become statistically non-significant if
p-values were corrected with the number of tests, the negative association of neuroticism in physical activity seems to be consistent across both self-reported and accelerometer-measured leisure time physical activity. Based on the sensitivity analysis (the association was attenuated from β = −.07 to β = −.06), this association seems to be at least partially explained by health status. Additionally, the association may have been underestimated, because women who scored high in neuroticism were less likely to provide acceptable accelerometer data. People who score high in neuroticism may have a tendency to avoid the intensive stimulation offered by physical activity [
14]. The negative feelings that are often experienced by individuals who score higher on neuroticism, such as anxiety and depression [
9], may also decrease the willingness to be physically active. However, physical activity interventions may help to reduce symptoms of anxiety and depression [
40], and hence people with high neuroticism could potentially benefit from physical activity interventions. Further research should address ways of promoting physical activity among people who score high on neuroticism. For example, good barrier self-efficacy may help such individuals to overcome the negative effects of high neuroticism on physical activity [
41].
Interestingly in this study, the negative association of neuroticism was only found with leisure time MVPA, and not with whole-day MVPA or whole-day or leisure time light physical activity. People high in neuroticism typically have lower occupational status [
42] and may therefore be more physically active during their working hours. Moreover, personality may play a more important role in leisure time physical activity, as people are likely to have more control over their physical activity during their leisure time than work time. Given that leisure time and occupational physical activity may have different links with health [
43] and that MVPA is more beneficial for health than lighter intensity activities [
44], it would be important to pay more attention to neuroticism as a predictor of leisure time MVPA. However, due to the observational nature of this study, the causal relationship between neuroticism and leisure-time MVPA remains unclear and warrants further research.
The associations found among middle-aged women were not observed in the sample of older adults. This is surprising, since previous studies with large samples and meta-analyses suggest robust associations between personality traits and self-reported physical activity without a moderator effect of sex or age [
13,
14]. However, similar finding was also reported by Čukić and colleagues [
21], who found no associations between personality traits and accelerometer-measured step counts among older adults. The physical activity levels of the older adults in the PASSWORD sample showed a rather narrow range and low variance, as being sedentary or at most moderately active were among the inclusion criteria [
27]. The small proportion participating in regular physical activities and sports is likely to explain the absence of any associations between personality traits and physical activity in this sample. Terracciano and colleagues [
45], who studied a sample of US older adults, found that while personality traits had essentially no associations with resting metabolic rate and energy expenditure at normal walking pace, lower neuroticism and higher extraversion were associated with walking significantly faster and higher energy expenditure at peak walking pace. This pattern suggests that personality traits are less predictive of activity level in samples limited to individuals or activities with low energy expenditure.
To our knowledge, this was the first study to investigate the role of personality traits in discrepancies in the two different physical activity outcomes. A weak negative association between neuroticism and a discrepancy between scores was found among older adults. In line with previous results showing that individuals who score high in neuroticism are more likely to over-estimate their weight [
25,
46], our finding suggests that such individuals may also tend to underestimate their level of physical activity. Neuroticism describes a predisposition to experience negative feelings, and hence this result may support this negative way of looking at life. This would be a fruitful area for future studies using more detailed personality questionnaires and more comparable physical activity measures.
Our discrepancy analysis was limited by the use of physical activity measures that are not directly comparable. The self-report items asked about mean monthly activity, whereas accelerometers were used for seven consecutive days. In addition, self-reports are informative about subjective intensity, while the cut-point values for accelerometer-measured MVPA do not usually take into account the fitness level of the user and may underestimate the amount of, at least, moderate intensity activity, especially among older adults [
15,
17]. Moreover, in the samples used in this study, accelerometers are likely to have underestimated physical activity among persons who participated in cycling, water-based activities or upper-body training. Therefore, further studies on the role of personality in the discrepancy between physical activity measures are needed.
This study was limited by the absence of the other three Five Factor Model personality traits, namely conscientiousness, openness and agreeableness [
9]. Because personality was not the primary focus in the ERMA and PASSWORD studies, longer questionnaires assessing all five personality traits were not included in the baseline questionnaires in either study. Previous studies have shown that both conscientiousness and openness are positively associated with physical activity [
13,
14] and it would also have been interesting to study these traits. Additionally, the Five-Factor Model personality traits comprise lower-order facets, which offer more detailed information about the traits [
46]. For example, the positive association between extraversion and physical activity is mainly explained by the facet of extraversion termed “activity” [
20]. The inclusion of facet-level personality characteristics could have offered more information on the associations between personality and physical activity. Another weakness of this study was the relatively low internal consistency of the 19-item short form of the Eysenck Personality Inventory, especially in the ERMA sample; however, removing any item would not have improved the Cronbach’s alpha values. It is also possible that personality traits influence the willingness to participate in different types of trials. Unfortunately, information on those who declined to participate in the ERMA and PASSWORD studies was not available, and hence they cannot be compared on personality traits with the participants.
It is important to bear in mind that although identical measures of personality and self-reported physical activity were used in both samples, the accelerometers and ways of analysing raw accelerometer data differed between the two studies. Hence, the samples are not directly comparable in their absolute levels of accelerometer-measured physical activity. However, the accelerometer data were analysed with previously validated methods in both studies [
35,
38] and it is unlikely that the slightly different cut-points for physical activity intensity would have affected the associations between personality traits and physical activity.
The use of two samples and of both accelerometers and self-reports to assess physical activity are the major strengths of this study. Although the PASSWORD sample was relatively inactive and the ERMA sample did not include men, both samples are large compared to previous studies using accelerometers [
18‐
20,
22] and the results thus contribute to knowledge on the relationship between personality and different measures of physical activity. The ERMA sample showed relatively high amount of MVPA per day (whole day 49.7 ± 25.9 min) compared, for example, to Canadian women aged 40–59 (approximately 24 min/day) [
3] and Norwegian women aged 20–64 (36 min/day) [
4]. However, this seems to be in line with country-level comparisons showing that, among the high-income countries, Finland has one of the most physically active general populations [
1]. The amount of MVPA in the ERMA sample was close to the mean of middle-aged women in Finland [
47,
48] (see also Additional File
1).The results can be generalized to healthy middle-aged women and to sedentary or at most moderately active older adults.
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