Introduction

There is now considerable evidence that prolonged sitting can have adverse consequences for health. A recent systematic review and meta-analysis showed that sedentary time is associated with increased mortality and morbidity [1]. Physical activity is known to prevent premature death [2]. According to the review by Biswas et al, the increased health risk associated with sedentary behaviour appears to be independent of physical activity [1], although a subsequent systematic review suggested that the size of the mortality risk associated with sedentary time is reduced in those who are physically active and that the risk disappears in those who are most active, defined here as 60–75 minutes per day of moderate intensity activity [3]. There is a need to identify modifiable risk factors for sedentary behaviour [4, 5]. This may be particularly important for older people who spend a higher proportion of time sitting than younger age groups. In a systematic review, nearly 60% of those aged ≥60 reported sitting for ≥four hours a day, while in a survey where sedentary behaviour was measured objectively, 67% were sedentary for >8.5 hours per day [6].

One factor that might help determine both how sedentary and how physically active older people are is their attitude to ageing. There is evidence from cross-sectional surveys that older people who have a more negative attitude to ageing—seeing it as a time of ill health, loneliness, loss of ability to perform usual activities, and loss of independence—report lower levels of physical activity [7–10]. A limitation of these cross-sectional studies is that it is unclear whether attitudes to ageing influence activity patterns or vice versa. Longitudinal evidence on the relationship between attitudes to ageing and physical activity is sparse, but two studies have found that having a more positive view of ageing is associated with an increase in self-reported physical activity over time [10, 11]. In one of these studies, a positive attitude to ageing was predictive of walking more frequently six years later [10]. To our knowledge, there have been no longitudinal studies into the relation between attitudes to ageing and sedentary behaviour. Furthermore, existing longitudinal evidence on attitudes to ageing and physical activity is based solely on self-reported activity which could be subject to recall and social desirability bias. Establishing whether having a negative attitude to ageing is a risk factor for sedentary or walking behaviour in older people is important, as evidence from interventions suggest that such attitudes are modifiable [12], so could potentially lead to behaviour change.

We used data from the Lothian Birth Cohort 1936 to investigate the prospective relationship between attitudes to ageing at age 72 years and objectively measured sedentary behaviour and physical activity at age 79. Our aim was to examine whether having a more positive attitude to ageing was predictive of being less sedentary and taking more steps around seven years later.

Materials and methods

Results

Of 374 people invited to participate, 304 were given an activPAL and 302 returned them. We excluded 31 participants (incomplete diary (n = 7), activPAL data quality (n = 5), and <7 days of data (n = 19)). We analysed only those who had 7 days of data so no assumptions about wear time would have to be made. Analyses are based on 271 participants. Mean age at the time of activPAL data collection was 79.1 (0.44) years.

Preliminary analyses showed that responses to the two items on exercise in the Attitude to Ageing Questionnaire were correlated with the activPAL measures collected around seven years later. People who endorsed the item ‘It is important to take exercise at any age’ more strongly spent less time sedentary (rho -0.174, p = 0.005), had a higher step count (rho = 0.325, p<0.001), and made more sit-to-stand transitions (rho = 0.235, p = 0.001). Similarly, people who endorsed the item ‘I keep as fit and active as possible by exercising’ more strongly spent less time sedentary (rho = -0.136, p = 0.027), had a higher step count (rho = 0.357, p<0.001), and made more sit-to-stand transitions (rho = 0.124, p = 0.045).

To avoid spurious correlations with the activPAL measures produced by construct overlap between measures, we calculated scores for the Physical change subscale after excluding the two items on exercise. Cronbach alpha statistics for Physical change, Psychosocial loss, and Psychological growth were 0.77, 0.82 and 0.75 respectively.

Table 1 describes the characteristics of the participants. Participants who spent a greater percentage of time sedentary tended to have a lower average daily step count (rho = -0.475, p<0.001), but sedentary time was not associated with number of sit-to-stand transitions. Participants having a higher average daily step count tended to make more sit-to-stand transitions (rho = 0.265, p<0.001). Participants who had a more positive attitude to psychosocial loss (indicated by lower scores) tended to make more sit-to-stand transitions (rho = -0.159, p<0.001); participants with more positive attitudes to physical change tended to have a higher daily step count (rho = 0.152, p<0.01). Scores on the domain of psychological growth were not associated with any activPAL measure. A higher percentage of sedentary time was associated with being female, having a higher BMI, and spending less time in full-time education. Taking more steps per day was associated with having fewer chronic physical diseases, lower levels of depressive symptoms, lower BMI, and lower scores on the Townsend disability scale. Making more sit-to-stand transitions per day was associated with lower BMI and lower scores on the Townsend disability scale.

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Table 1. Characteristics of the participants at age 72 years and their rank order correlations with the sedentary and walking behaviour measures at age 79 years (n = 271).

https://doi.org/10.1371/journal.pone.0197357.t001

We examined whether the relationships between attitudes to ageing and the activPAL measures varied by sex. Of nine interactions examined, only one was statistically significant (p = 0.028), but after control for multiple testing [25], this p value did not reach statistical significance (p = 0.25). We therefore analysed men and women together and adjusted for sex.

Table 2 shows regression coefficients (95% confidence intervals) for percentage of time spent sedentary, logged average daily step count, and logged average daily sit-to-stand transitions separately for a standard deviation (SD) increment in each attitude to ageing domain score. Results are shown adjusted first for sex, and then further adjusted for the potential confounding factors—education, depressive symptoms, number of chronic physical diseases, BMI, and Townsend disability score.

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Table 2. Results from linear regression analyses of measures of sedentary behaviour at age 79 according to scores on attitudes to ageing scales at age 72.

https://doi.org/10.1371/journal.pone.0197357.t002

There were no associations between any of the attitude to ageing domains and percentage of waking time spent sedentary. There were no associations between attitudes to psychosocial loss or psychological growth and logged average daily step count. In the sex-adjusted model, participants who had a more positive attitude with regard to physical change took significantly more steps per day: for a SD increment in score on this domain, average daily step count increased by 1.5% (95% CI 0.6%, 2.4%). This remained significant after correction for multiple testing (p = 0.012) [25]. However, this relationship was no longer significant after adjustment for the other covariates, in particular depressive symptoms, BMI and Townsend disability score. In the sex-adjusted model, there was a significant association between having a more negative attitude to psychosocial loss and logged average daily sit-to-stand transitions. This association did not survive control for multiple testing (p = 0.10). It was attenuated after adjustment for the other covariates. There were no associations between the other attitudes to ageing subscales and logged average daily sit-t0-stand transitions.

As noted in the methods, we chose to exclude two items on exercise from the 8-item physical change domain to avoid spurious correlations with the activity measures. Had we retained the two items on exercise in the physical change domain, the associations between scores on this domain and amount of time spent sedentary or number of sit-to-stand transitions would have been very similar to those found when they were excluded. With the retention of these exercise items, the association between scores on this domain and average daily step count would have been slightly stronger and would have remained significant after adjustment for potential confounders: for a SD increment in score, average daily step count increased by 1.59% (0.86%, 2.31%) after adjustment for sex, and by 0.89% (0.14%, 1.64%) (p = 0.020) after further adjustment for potential confounding variables. However, this association was not statistically significant after correction for multiple testing (p = 0.12).

Discussion

In this longitudinal study, we found no evidence that having a more positive attitude to ageing at age 72 was predictive of daily time spent sedentary or sit-to-stand transitions at age 79. In sex-adjusted analyses, people who had a more positive attitude with regard to physical change had a higher average daily step count, but the effect size was small and was attenuated to non-significance after adjustment for potential confounding factors.

Negative stereotypes of ageing are common [26]. Such internalised stereotypes may have adverse consequences for health in older people [27, 28]. Having a more negative perception of ageing has been associated with declines in cognitive ability [29] and in physical function [30, 31] and with an increased risk of dying prematurely [22, 32, 33]. Qualitative evidence in older women suggests that it is common for them to feel encouraged by society, family, and friends to sit rather than be physically active [19]. Although there is some longitudinal evidence to suggest that people who have a more positive attitude to ageing may be more physically active, as based on self-reports [10, 11], the results of the current study fail to confirm this. They also suggest that sedentary behaviour is unlikely to be a mechanism underlying the associations found in other studies between attitudes to ageing and adverse health outcomes.

According to the social psychologists, Ajzen and Fishbein, attitudes are more likely to predict behaviours if there is a strong degree of correspondence between attitude and behaviour such that both involve the same action, target, context and time element [34], in other words, both are measured at equivalent levels of specificity. There is considerable evidence in support of this principle of correspondence [35]. If we had collected data on participants’ attitudes to being physically active or sedentary, or on their attitudes to these same behaviours seven years in the future, we might have obtained stronger associations with our objective measures of walking and sedentary behaviour than those we found with the attitudes to ageing subscales which represent broader constructs.

Our findings are in contrast with those of two longitudinal studies which reported that a positive attitude to ageing was associated with increases in self-reported physical activity in older people over periods of 2.5 and 6 years respectively [10, 11]. In one of these studies, attitude to ageing was assessed with a 4-item scale about ageing as a time of personal growth and development [10], similar in content to the psychological growth subscale used here. The other study used the 5-item attitudes towards own ageing subscale of the Philadelphia Geriatric Center Morale Scale [11]. This includes items similar in wording to some of those included in the psychosocial loss and physical changes subscales used here, but has been criticized for ignoring the fact that ageing can be a time of development and positive change [18]. Neither of the attitudes to ageing scales used in these two longitudinal studies included items about physical activity [10, 11], yet despite what might seem a lack of correspondence between the attitude being assessed and the behaviour under study, they were significantly associated. One explanation for the inconsistency between these findings and those of the current study might be our use of objective measures of activity and sedentary behaviour rather than self-report.

Responses to two items in the Attitudes to Ageing Questionnaire that referred specifically to exercise—‘I keep as fit and active as possible by exercising’ and ‘It is important to take exercise at any age’—were significantly correlated in the expected direction with the objective measures of sedentary and walking behaviour made seven years later, confirming that self-reports of exercise have some validity. We chose to exclude these two items when calculating scores on the 8-item Physical change domain of the Attitudes to Ageing Questionnaire in order to avoid spurious correlations between these scores and the objective measures of sedentary and walking behaviour produced by the inclusion of these items on exercise. It might perhaps be argued that they should have been retained. The results from an analysis using all 8 items suggest that if we had included the two items on exercise in the physical change domain, our findings on the relationship between attitudes to physical change and objectively measured walking and sedentary behaviour seven years later would be essentially the same as those we obtained when they were excluded.

Our study has a number of strengths. The activPAL accelerometer provides gold-standard objective measures [15, 16]. Our analyses are based on accelerometry data for a seven day period thus minimising any systematic variation over the course of the week. Over 90% of participants provided a full week of data. Attitudes to ageing were assessed using a well-validated questionnaire [18]. A further strength is that we were able to take account of a range of potential confounding factors, including depressive symptoms, comorbidity, BMI and difficulties with activities of daily living. One potential weakness of our study is that attitudes to ageing were assessed on average seven years prior to the collection of activPAL data. However, a previous longitudinal study has shown that attitudes to ageing are predictive of frequency of self-reported walking six years later [10], so it was not unreasonable to hypothesise that in the current cohort we would find a similar association using objectively measured activity data. A further limitation is that we had no contemporaneous measure of sedentary and walking behaviour so were not able to examine whether attitudes to ageing were predictive of change in these behaviours.

In our ageing populations, understanding the extent to which internalised negative stereotypes about age affect health outcomes or behaviours in older people has particular relevance (28). In this study, we found no evidence that attitudes to ageing at age 72 years were predictive of objectively measured sedentary or walking behaviour around seven years later. Future studies should examine whether attitudes to ageing are associated with objectively measured walking or sedentary behaviour at the same time as the existence of such an association could inform the development of interventions, and investigate whether the relationship between attitudes to ageing and these outcomes varies over the wide age range of older adults. It might also be informative to explore whether specific attitudes about exercise or sitting in later life are better predictors of objectively measured walking or sedentary behaviour in older people than the broader-based attitudes to ageing scales.

Acknowledgments

We thank the Lothian Birth Cohort 1936 members, investigators, research associates and team members. We also thank the radiographers at the Brain Research Imaging Centre, and the research nurses and Genetics Core staff at the Wellcome Trust Clinical Research Facility. The named authors present the study on behalf of the Seniors USP Team, which comprises: Dawn A Skelton (PI), Sebastien Chastin, Simon Cox, Elaine Coulter, Iva Čukić, Philippa Dall, Ian Deary, Geoff Der, Manon Dontje, Claire Fitzsimons, Catharine Gale, Jason Gill, Malcolm Granat, Cindy Gray, Carolyn Greig, Elaine Hindle, Karen Laird, Gillian Mead, Nanette Mutrie, Victoria Palmer, Ratko Radakovic, Naveed Sattar, Richard Shaw, John Starr, Sally Stewart, Sally Wyke.