The findings show that each additional serving of fruit and vegetable or 15
min brisk walk per day, was associated with approximately 10% increase in the odds of reporting health as good or better among women and men. The effect size remained statistically significant when all three lifestyle behaviours were included in the model, and after adjusting for BMI, smoking, long-term illness and socio-demographic characteristics (education, marital status and housing tenure). Taking into consideration the burden of chronic diseases, an increase in F&V intake and LTPA of this size may have a substantial impact on public health. However, these cross-sectional findings need to be confirmed longitudinally.
Recent large prospective studies show that compliance with multiple healthy behaviours is associated with the reduced risk of mortality in a dose–response way [5
]. For example, the mortality risk associated with compliance with four compared to zero health behaviours (never smoked, healthy diet, adequate physical activity and moderate alcohol use) was equivalent to being up to 14
years younger in chronological age [5
]. The study by Ford et al. also showed that the combined impact of a healthy diet and adequate physical activity reduced the risk of all-cause mortality by 25% [5
]. Another longitudinal study, examining health behaviours and quality of life, suggest that physical activity is the key factor, superior to fruit and vegetable consumption and sedentary time (viewing), when influencing individual’s mental health and quality of life [41
]. On the other hand, an untargeted increase in physical activity has been reported in interventions to promote fruit and vegetable consumption [42
]. Furthermore, randomized control trials have shown that individuals that adopted one healthy behaviour are more likely to adopt another healthy behaviour, and that there are even greater benefits with reducing bundle risk behaviours simultaneously [43
]. Although these studies were among adults in general and did not focus specifically on older adults aged 55–65
years, the results give justification for looking at health behaviours in combination, and the importance to examine both additive and synergistic effects on health outcomes. They also give insights into the quantity and quality of life that can be potentially gained when adopting healthy lifestyles. The results from the present study show similar association for F&V and LTPA with self-rated health, and provide further support that even small differences in lifestyle behaviours may make a big difference to health in the population.
Worldwide it is well-recognised that the risks for chronic disease are escalating, and the future burden (social and economic) will be largely determined by current lifestyle behaviours [10
]. In Australia, a majority of older adults aged 55–64
years have three or more behavioural risk factors for chronic disease, and low intake of fruit and vegetables together with lack of physical activity is the most common combination [45
]. Hence, to bring about an increase in F&V intake or/and LTPA could result in postponement of age-associated diseases which allows independent living for a longer period of time [1
]. However, for optimal promotion of healthy lifestyles in older adults, we need to understand both prevalence of health behaviours and associations among such behaviours. The low correlation coefficients, between F&V intake, LTPA and ST in the present study, indicate that they have little if any linear correlation, or that confounding variables might be involved. A range of personal, social, and environmental factors, (above and beyond the socio-demographic factors included in the present study), are important influences on food consumption, physical activity and sedentary behaviours [17
]. A better understanding of these influences among older adults is necessary to take into account the specific life-stage context.
Considering the growing evidence of an association between sedentary behaviour and different health outcomes [2
], the lack of an association between ST and self-rated health was unexpected. One reason could be that ST in older adults might be more related with objective health indicators [4
]. Another explanation could be the measure of ST. Although the sitting measure in the IPAQ has acceptable reliability and validity among adults aged 18–65
], perhaps the measure did not perform so well among Australian adults in this age group. A limitation of the sitting measure in IPAQ is that it does not distinguish between sitting in different domains, such as work, transportation, domestic and garden, and leisure- time. Therefore, associations between discretionary sitting and self-rated health could not be examined, as was done for LTPA. When specific sedentary behaviours are examined the most common sedentary leisure-time behaviour is TV viewing time [8
The positive and negative interaction effect (for women and men, respectively) between ST and F&V was also surprising. This means, that the simultaneous influence of ST and F&V on self-rated health is not additive. Instead, the association between F&V and self-rated health is dependent on ST and additional time spent sitting affects this association differently in women and men. Therefore, among men the association between F&V and self-rated health strengthens with less time spent sitting (<10
b). However, the reverse effect for added time spent sitting (>5
hr/day) in women are more difficult to explain (Figure
a). It is possible that the different associations for men and women are a result of different patterns of sitting time, for example, prolonged periods versus intermittent sitting bouts however there is limited research on sitting time among this age group [3
]. Objective measures of sedentary time in US shows that male older adults (>60
years) are more sedentary than their female counterparts [47
]. However, an international comparative study of sitting time among adults in 20 countries did not find any gender differences [17
]. Consequently, more research is needed to clarify associations with sedentary behaviour in this age group.
One limitation of this study is the use of self-reported data which may be hampered by recall biases such as social desirability (including cultural and gender differences), and over- or under-reporting [48
]. The modest response rate, which can introduce bias into study results, is also acknowledged. Although there were some differences between respondents and non-respondents, the distribution did not differ compared to Australian national data for self-rated health and health risk factors (smoking, BMI, fruit and vegetable consumption, exercise level) in the same age group [15
]. Even if selection bias cannot be ruled out (e.g. those that agreed to participate could have healthier behaviours than nonparticipants), the data were obtained from a relatively large, random sample of older adults sampled from the Australian Electoral Commission electoral roll (voting is compulsory for person aged 18
years and over), which limits the risk of self-selection bias. The cross-sectional design and inability to determine causality of effect is also a limitation. Thus, it is difficult to assess which factors are determinants and which are consequences in the association between F&V intake, LTPA, ST and self-rated health. Though we found no association between long-term illness and physical activity, it cannot be excluded that some individuals do not take part in physical activity and/or might be more sedentary due to various health problems, including mental health problems. However, the WELL study is designed as a prospective cohort so we will be able to investigate the findings longitudinally. Furthermore, the ability to concurrently explore a set of key factors that may have an impact on older adult’s future health, with sufficient power and adjusted for important confounders is a strength of this study. In light of an acceleration of the ageing of the global population [10
], and bearing in mind that self-rated health is strongly associated with successful healthy ageing, identifying its determinants is of importance for understanding the underpinnings of good health in later life.