Health-related competencies or health literacy (HL) are defined as “cognitive and social skills which determine the motivation and ability of individuals to gain access to, understand and use information in ways which promote and maintain good health” [1
]. Studies show that high HL is associated with healthier lifestyles and health-promoting and -maintaining behaviors in healthy adults [2
] as well as in people with cardiovascular [3
] or metabolic diseases [4
]. In recent years, many studies have investigated the quality of HL in the population. The “European Health Literacy Survey” (HLS-EU) showed that almost one in two respondents (47%) have insufficient HL [5
]. In regard to the different areas of HL, a study of the German population showed that 20.8% of the respondents had inadequate HL in the field of health-promoting behavior, compared to 11.5% for prevention and 10.3% for dealing with diseases [6
The validated structural model of HL introduced by Lenartz [7
] and Soellner et al. [8
] (see Figure 1
) provides a possible theoretical explanation of the influence of HL on health behavior. In short, health behavior and health
are the result of two basic and six secondary abilities, all of which define HL. In this model, basic knowledge of health
and basic skills concerning health
build the foundation, e.g., the ability to read health-related manuals [9
] and understand terms describing the body [7
]. These basic abilities influence the secondary abilities. Health-related self-perception
includes the perception of one’s own needs and feelings as well as the focus on internal and external processes (e.g., being aware of tensing up in certain situations), which again are part of self-regulation
]. Together with the willingness and ability to take responsibility for one’s own health (proactive approach to health
influences even more secondary abilities: Dealing with health information
describes the capability to understand health-related information and integrate it into one’s personal life. Someone with high self-control
is disciplined in pursuing personal goals [11
], whereas regulatory processes help to deal with self-congruent and -incongruent topics (self-regulation,
e.g., being able to relax) [11
]. Lastly, communication and cooperation
describes behavior which intends to establish and maintain good relationships with others [7
One of the most common methods in maintaining health and decreasing the risk of non-communicable diseases is physical activity (PA) [12
]. According to Lenartz’ model, people who have higher HL should also show more health behavior than people who are less health literate. Since PA is acknowledged as a healthy behavior, it is questionable if physically active people show greater occurrences of HL and vice versa. In fact, some studies show that training in HL for healthy adults [2
] as well as adults with chronic diseases [18
] leads to increased PA levels afterwards, thus supporting this assumption. However, the majority of results on the association between HL and PA were obtained with questionnaires and overall HL scores [18
]. Up to now, the association between objective PA data and HL has only been scarcely investigated in adults [19
]. Therefore, the aim of the present study is to investigate the relationships between the different aspects of HL and PA, not only with subjectively (questionnaire) but also with objectively (accelerometry) measured PA data. In line with the literature [2
] and the structural model by Lenartz [7
], we hypothesize a positive correlation between HL and both measures of PA.
The aim of the present study was to investigate whether a relationship between HL and PA measured by subjective and objective instruments exists. In total, the study population reported moderate to high values for HL and PA. The hypothesized positive correlation between HL and PA was only partly confirmed. Only one very low correlation could be observed for the subjective assessment of PA and one subscale of HL (self-perception). In regard to the objective PA levels, one medium correlation with the subscale proactive approach to health was found. Since the majority of HL subscales showed no connection to PA at all, these results indicate that not all aspects of HL might be equally important for promoting and maintaining healthy behavior.
The present study only partly confirms previous research which showed a connection between HL and PA [19
]. Neither the regression analyses nor the majority of the correlations showed significant associations between the subscales of HL and objective and subjective PA. Only the proactive approach to health
was statistically significantly correlated to objectively measured vigorous activity. A possible explanation for the correlation found might be that, according to Lenartz [7
], the proactive approach to health
includes having the awareness that health is not given but something that has to be worked for. One might assume that the proactive approach to health
plays an important role in participating in more intense activities, e.g., swimming or jogging [43
]. Such activities are mostly intentionally performed and planned. Therefore, it is likely that people taking responsibility for their own health engage in sport activities purposely. Previous studies on self-determination theory [44
] have shown that engagement in PA behavior increases if a person has autonomous forms of motivation and actively takes responsibility for their health [45
]. In line with this, a more detailed analysis of our results revealed that a proactive approach to health
correlates with leisure time MET minutes (r = 0.31, p
< 0.001) but not with work time MET minutes. This supports the assumption that if the importance of health-promoting behavior is internalized and a person takes active responsibility for showing such behavior, increased vigorous PA might be the result and be shown in leisure time.
In addition to those findings, a result that is controversial in relation to the literature was found: Lenartz’ assumptions and previous results, which postulated that a greater ability in perceiving inner and outer processes results in a healthier lifestyle and adaptive health behavior [47
], could not be affirmed. While the subjective PA data revealed only very low negative correlations with self-perception,
neither the regression analyses nor the data from the accelerometry showed any connection at all. A possible explanation for these results may refer to the perception of PA. As previous studies have shown, self-reported PA in terms of intensity and duration differs from data recorded by more objective tools [48
]. PA of moderate or vigorous intensity is often overestimated while sedentary behavior is frequently underestimated in relation to the respective objective data [50
]. Therefore, it stands to reason whether people with high self-perception are more precise when reporting their own PA. In this way, their reported PA might be lower than that of people with worse self-perception. This assumption is supported by psychology research which concludes that respondents are more accurate in their ratings when they are more self-aware [51
] as well as by the fact that no influence of self-perception
on the data measured by accelerometry was found.
Although the strongest correlation between HL and PA was found within the Actigraph GT3X+ data, it is questionable whether the objective measurement and the resulting more valid estimation of PA [53
] has a connection to general HL. Only a few HL studies have assessed PA with an objective device so far [2
]. Al Sayah et al. [19
] found a significant interaction between HL and subjectively assessed PA, but no interaction between HL and objectively measured PA. A study by Aldana et al. [2
] was able to observe a significant increase in PA by 30% after a health educational course. However, no correlation analysis between HL and PA was provided. Riecken [20
], on the other hand, was able to observe a significant correlation between HL and objectively assessed PA. Hence, the question of whether all or only certain aspects of HL relate to objective PA and PA in general is still unanswered. Further research with objective measures and larger sample sizes is needed to establish solid evidence regarding the relationship between HL and PA behavior.
The present study was conducted as a pooled analysis of three projects by the research association TRISEARCH, which were addressing different target groups. Due to the cross-sectional study design, testing the direction of causality between HL and PA was not possible. Moreover, large differences between the different target groups regarding age and sex were present. One project was conducted with apprentices, who were at the start of their working career and, therefore, much younger. Research showed that younger age was a significant predictor for lower HL levels [54
]. Additionally, the target group of working adults with health-related risk factors participated in a rehabilitation and prevention program, which was able to offer external support. Even if our population showed great heterogeneity, age and sex were entered as covariates into the analyses and therefore controlled. However, since not all studies recorded data on participants’ educational levels, body-mass index or socio-economic status, we could not include these as possible covariates. Hence, a potential bias cannot be ruled out.
In the present study, HL was assessed with a questionnaire generated by the German researcher Lenartz. This questionnaire is not yet as commonly used as the Health Literacy Questionnaire (HLQ) [55
]. The HLQ is a valid and reliable measurement of HL [55
]. In comparison to the HLQ, the Lenartz questionnaire fails in providing a global HL score but offers a differentiation on six subscales compared to the nine of the HLQ. This makes the questionnaire more compact and feasible. Furthermore, the Lenartz questionnaire focuses on the respondent’s self, whereas the HLQ focuses on dealing with the outside world and being resourceful [55
]. Additionally, the connection to the HL model of Lenartz [7
], which was used as a theoretical basis in the TRISEARCH projects, led to the decision to use the Lenartz questionnaire.
A problem that might occur when both PA and HL are measured via questionnaires is that both measurements underlie the probability of recall and social desirability bias. Recall or social desirability bias could, for instance, influence the participants’ response when recalling the length and occurrence of PA behavior [53
]. People tend to over-report their PA behavior [50
] and might be likely to show the same pattern in HL questionnaires. This could lead to a higher probability of gaining significant correlations between these two instruments. Our study is one of the few existing studies which included objective and subjective PA measurements, although, only a subsample had access to accelerometry because of limited resources and compliance of participants. The compliance of the participants wearing the accelerometer was also the reason why we chose the inclusion criterion of at least three days with at least ten hours of recorded data. The widely used recommendation by Trost et al. [59
] of at least 4 valid days, including at least one weekend day, would have further reduced the sample size to 92 participants. Nevertheless, the results regarding the association between HL and PA, as well as the influence of the HL subscales on the amount of MVPA, would have been similar. Thus, the inclusion criterion of three days was kept to maintain the larger sample size.
Due to these limitations, the generalizability of the Actigraph GT3X+ results must be treated with caution. Hence, further studies with objective measures of HL and healthy behavior are needed to improve the understanding of the underlying mechanisms of this relationship.