The objective of this cross-sectional study was to clarify putative determinants of SRH with an emphasis on the relationship between SRH and lifestyle factors in a large sample of urban citizens. As expected, female gender and more consistently disease status and healthcare use were associated with poor SRH, while significant variability of SRH putative determinants across age groups was monitored.
In the younger group, individuals reporting exercise less than one hour per week have poorer SRH, implying a particular awareness of the role of exercise on health among young people.
Concerning the middle age group, people with lower education level, past or heavy smokers and individuals dissatisfied with their sleep quality reported poorer SRH. Education was significant only in this age group, probably due to its higher correlation with putative socio-economic (and employment related) inequalities. Past and current heavy smokers seem to consider smoking habit more relevant to their health, possibly representing past reasons for quitting and worries of excessive smoking, respectively.
In the 50+ years old group, daily physical symptoms, increased BMI score and low sleep satisfaction, were associated with poorer SRH. Interestingly, the role of gender was not significant in the elders while BMI emerged as a new SRH determinant. The most consistent correlation was that of sleep dissatisfaction and poor SRH, even in younger people when subgroup analyses (good vs very good/excellent SRH) was performed. Moreover, sleep dissatisfaction was the only lifestyle variable associated with poor SRH in elders, even when higher level of significance was applied (0.001).
Overall, the explained variances of SRH from the youngest to the oldest age group were 12%, 28% and 30% respectively. The lower explained variance in the youngest group implies that other than the measured factors may determine SRH in younger people. We hypothesize that the lack of measured psychosocial factors, related mainly to interpersonal relationships or academic performance could account for this low percentage of explained variance. To test if such an assumption could be true, we repeated multivariate analyses separately for 15-19 years old and 20-29 years old people, considering that the younger group refers mainly to students of secondary education, while the second one represents students at university or labor force. For the first group, only sleep dissatisfaction correlated with poor health (OR 3.68, 95%CI 1.09 to 12.41, R square 0.05) and for the second one, variables were the same with the initial (e.g. 15-29 years old) group with little R square increase (explained SRH variance equal to 17%).
In the literature, there are a vast number of similar studies that differ in respect of participants' characteristics and measurement issues, a fact that hinders a complete "face-to-face" comparison with our own. However, our main findings are quite similar with those of the most pertinent previous studies, albeit in different cross-cultural settings, that have shown, the significant relations of SRH with smoking [17
], regular physical exercise [16
] and obesity [17
]. Finally, sleep quality, although differently assessed in various studies, seems to have an important relationship with SRH [16
]. Comparing our work to these pertinent studies, major measurement discrepancies were detected for exercise and sleep quality, although this did not affect their role in determining SRH. Overall, for exercise most surveys used validated questionnaires, sets of various questions on everyday physical activity or impressions about the level of fitness, while our measurement was more simplistic (more or less than one hour per week) mainly based on the usual recommendations by Greek physicians. The same straight-forward pattern describes sleep satisfaction, while other studies used validated questionnaires or questions relevant to sleep quality (e.g. hours of sleep).
On the contrary, we did not found any relationship between dietary habits or alcohol intake and SRH supported by previous studies [17
]. We hypothesized that cross-cultural differences might account for these differences [38
]. We should note, however, that in other studies dietary habits were measured according to servings per day for each food category [18
] or in the context of health behaviors (choices) [22
], while we used a more crude measure of consumption (days per week), which it might has affected our results. We did not found significant relationship between religiosity and SRH as few other studies also did [27
]. We used two arbitrary open questions to address both extrinsic (church attendance) and intrinsic (praying) religiosity, which is not common among other studies. Religiosity is a complex variable, which should incorporate not only praying, or attendance to ceremonies, but also psychosocial variables pertinent to social networks and social recourses or support [40
]. As such, religiosity could be a marker of various social-related factors and should be regarded with caution. Perhaps spirituality may be taken into account in future studies [41
It is acknowledged that this study has a number of limitations. Firstly, cross-sectional analyses cannot infer causality among measured factors. Secondly, measurements are mainly based on self-report increasing the likelihood of information and recall bias. Seasonal variation in responses during the one year period of the study may contribute to information bias. Moreover, inter-interviewer variability and issues with regard to social communication (e.g. social desirability) may more likely introduce measurement bias than simple questionnaire administration, but interviews have the advantage of minimizing missing values, which was the case in our study. Thirdly, low participation rate (53%) could introduce a selection bias and impair generalizability, although no cluster of low participation rate among regions was noted. Fourthly, dietary cut-offs were made according to the guidelines of Mediterranean diet without including information about the level of individuals' awareness to these directions. As written earlier in the introduction, SRH is subject to individual's perceptions and expectations, so a poor informative status about diet could deviate the association of this lifestyle matter with SRH. Finally, we did not include psychosocial variables which could be putative mediators or moderators of the lifestyle-SRH relationship.