Relationship among lifestyles, aging and psychological wellbeing using the General Health Questionnaire 12-items in Japanese working men

Abstract

Introduction. The relationship among lifestyle, aging and psychological wellbeing was evaluated in Japanese working men.

Methods. Self-administered questionnaire on six lifestyle factors and the General Health Questionnaire 12-item version (GHQ12) were administered to 3306 male workers. Health practice index (HPI) was calculated as a desirable lifestyle score by summing up each binary lifestyle score (0, 1), ranging from 0 to 6. To check validity of the study outcome, the authors repeated twice with 1 year interval. HPI was categorised into three groups by the score of 0–2, 3–4 and 5–6.

Results. The number of subjects categorised by HPI was 532, 1967 and 807, respectively. The mean value of GHQ12 significantly decreased as the HPI increased by adjusting age. Multiple regression analysis was conducted to predict GHQ12 by six lifestyle scores, and age, sleep, night snacking and exercise were significantly related to GHQ12. Multiple logistic regression analysis was conducted and age in 50s, two-shift work, sleep, night snacking and exercise were significantly associated with GHQ12.

Conclusion. Although cause–effect relationship cannot make clear, some of desirable health practices and aging were closely related to psychological wellbeing judged by GHQ12.

Keywords:

• Lifestyle
• health practice index
• the General Health Questionnaire 12-item version
• aging

Introduction

Lifestyle factors including smoking, drinking, exercise, eating habit and sleeping are well known to be associated with health status such as morbidity and mortality [1–3]. Mental health status such as depressive state was also closely related to lifestyle factors, although cause–effect relationship cannot be clarified.

Healthy life status has been recommended to keep health status from the aspect of prevention. Once some problem on health appears, keeping healthy lifestyle is difficult. To keep productivity of industry, desirable lifestyle should be continuously paid attention. As a political strategy, prevention on mental and physical distress has been screened such as overwork prevention program by questionnaire survey. In addition to point check, education on continuous self-check procedure should be broadly conducted.

The General Health Questionnaire 12-item version (GHQ12) is a short form of original 60-item, which is a self-administered screening inventory to detect non-psychotic psychiatric illness [4,5]. The GHQ12 is specified to detect psychological wellbeing, although there is a recommendation to split into two or three factors by confirmatory factor analysis [6,7]. According to an opinion [8], the authors adopted total score of GHQ12 and analysed the relationship between GHQ12 and lifestyle factors.

Recently, economic instability has also made job stress widely and strongly to working men, and an urgent strategy is required to keep health status. In the present study, cross-sectional study was conducted in conjunction with annual health examination to know the relationship between lifestyles and GHQ12 as a screening tool for interruption of psychological wellbeing.

Subjects and methods

In spring of 2008, we made survey with a population of Japanese workers (3428 men and 141 women) ranging in age from 35 to 59 years who were working at a car-manufacturing company, Japan. As the number of women was relatively small, they were excluded from the subsequent analysis. Subjects receiving medication were included in this study. A questionnaire was administered to the subjects when they underwent their annual health examination mandated by law. As there were deficits of data on self-administered questionnaire, data for 3306 participants (96.4%) were finally included in the analysis.

The work schedule, lifestyle and medical history of the subjects were determined based on a self-administered questionnaire. The work schedule of the subjects was determined based on the answer to the question: ‘What is your usual work schedule, day, two-shift, or three-shift work?’ Day workers (n = 1848) were defined as subjects without any night work in their usual work schedule. The time schedule for day work was 08:00 to 17:00 h. Shift workers were divided into two-shift workers (n = 1211), with each shift starting at 06:30 or 15:00 h, and three-shift workers (n = 195), with the shifts beginning at 06:30, 14:30 and 22:30 h; the shifts rotated on a weekly basis. The number of unclassified subjects was 52. There were five work days per week. The rotating shift work was ‘discontinuous’ when it was interrupted in the weekend. There was no clear order in the direction of rotation, that is, clockwise or counterclockwise. Information on the length of the shift work experience and specifications about changes between shift/day work schedules during the working life, including past work experiences, could not be obtained.

The authors obtained informed consent from each of the study participants for participation in the study, and the study protocol was approved by the ethics committee of the company where they worked.

Definitions of the three lifestyle-related variables

Lifestyle-related covariates in this analyses included binary data on smoking status (1 = never smoked or ex-smoker; 0 = current smoker), alcohol use (1 = never drinker or not everyday drinker; 0 = everyday drinker), subjectively sufficient sleep (1 = Yes; 0 = No), habitual exercise (1 = not less than one hour exercise including walking everyday; 0 = other), breakfast (1 = more than four times per week; 0 = other), and night snacking (1 = not more than two times per week; 0 = other). These criteria were modified version of health practice presented by Berkman and Breslow [3]. Health practice index (HPI) was calculated by summing up of each score, ranging from 0 to 6.

Psychological wellbeing

The 12-item version of the GHQ12 was administered. The original version of the GHQ12 was developed by Goldberg to measure psychological distress or to quantify the degree of psychological strain in an individual [5]. The GHQ12 is sensitive for detecting psychological strain and is an established and effective epidemiological approach for determining the prevalence of psychological disturbances in a normal population [9–11]. Ill-health indicators are assumed to represent relevant stress-related outcome variables; hence, the GHQ has been used in a variety of studies to evaluate the stress response. The rating scale is a behaviourally anchored scale consisting of four options: ‘Better than usual’, ‘Same as usual’, ‘Worse than usual’ and ‘Much worse than usual.’ A Likert-style scoring procedure can be applied to this four-point scale, with ‘Better than usual’ representing 0 point and ‘Much worse than usual’ representing 3 points, with higher scores corresponding to poorer health. In the present study, however, the authors utilised the ‘GHQ-scoring’ method, in which the first two anchors, ‘Better than usual’ and ‘Same as usual’, were scored as 0 and the last two anchors, ‘Worse than usual’ and ‘Much worse than usual’, were scored as 1. Namely, the first two anchors represent the non-presentation of symptoms and are thus both scored as 0, while the last two responses represent the presentation of symptoms and are therefore scored as 1.

Statistical analysis

Multiple comparison by Tukey's test was conducted if analysis of variance by the HPI was significant. Multiple regression analysis and logistic regression analysis were conducted to estimate the prediction ability of GHQ score by lifestyle factors and age. SPSS 16.0 for Windows (SPSS Japan, Tokyo) was used for the statistical analysis. p < 0.05 was considered to denote statistical significance.

Results

From the distribution of HPI (Figure 1), the authors categorised HPI into three groups by the score of 0–2, 3–4 and 5–6. The number of subjects in each group was 532, 1967 and 807, respectively. There was a significant difference of GHQ12 scores among three groups (Table I). As the mean value of GHQ12 significantly decreased according to age (Jonckheere–Terpstra test p < 0.001), the authors also analysed ANOVA stratified by age. Except 50–54 years of age, there were significant differences among three groups stratified by HPI. There were significant difference in three combinations by Tukey's multiple comparison in age of 40–44, 45–49, 55–59 and total. Subjects in age of 35–39 showed significant difference between subjects with 5–6 HPI and 0–2 HPI or 3–4 HPI (Table I).

Table I.  Mean and standard deviation of GHQ12 stratified by health practice index (HPI).

Age	HPI 0–2		HPI 3–4		HPI 5–6
	N	Mean, SD	N	Mean, SD	N	Mean, SD
35–39	134	6.4, 3.50$	497	5.9, 3.77$	198	4.7, 3.50
40–44	169	6.9, 3.49*	547	5.9, 3.69*	202	4.7, 3.72*
45–49	99	7.3, 3.38*	382	5.6, 3.83*	161	4.7, 3.68*
50–54	61	5.1, 3.58	245	5.0, 3.68	92	4.4, 3.57
55–59	69	5.8, 3.63*	296	4.6, 3.62*	154	3.4, 3.20*
Total	532	6.5, 3.55*	1967	5.5, 3.75*	807	4.4, 3.57*

*There were significant differences among three groups stratified by HPI. In addition, the italic value was significantly lower than $ (p < 0.05).

Figure 1.  Distribution of health practice index.

Stepwise multiple regression analysis was conducted to predict GHQ12, and age, sleep, night snacking and exercise were significantly related to GHQ12 (Table II). Adjusted coefficient of determination was 0.124. From the negative relationship, the above mentioned three desirable lifestyles were positively associated with psychological wellbeing. As non-parametric Jonckheere–Terpstra trend test showed, GHQ12 became lower as they became older by adjusting several lifestyle factors.

Table II.  Determinants of GHQ12 by using stepwise multiple linear regression analysis.

Independent variable	B	SE	β	Significance
Satisfactory sleep	−2.33	0.12	−0.31	<0.001
Age	−0.05	0.01	−0.10	<0.001
No frequent night snacking	−0.71	0.17	−0.07	<0.001
Regular exercise	−0.46	0.13	0.06	<0.001

B, non-standardised regression coefficient; SE, standard error; β, standardised regression coefficient.

This statistical procedure includes age and six lifestyle factors. Each desirable lifestyle was categorised as 1, and subjects who have no desirable lifestyle were categorised as 0.

Multiple logistic regression analysis was conducted and odds ratios (95% confidence interval) of age in 50–54, age in 55–59 compared with age in 35–39, satisfactory sleep, habitual exercise, not night snacking, and two-shift work compared with day work for increased GHQ12 (≥4) were 0.68 (0.52–0.88), 0.66 (0.52–0.83), 0.34 (0.29–0.40), 0.81 (0.69–0.94), 0.60 (0.48–0.76) and 0.81 (0.69–0.95), respectively (Table III).

Table III.  Odds ratios and 95% confidence intervals of several factors to predict elevated GHQ12 (≥4) by logistic regression analysis.

Variables	Control	Metabolic syndrome
		OR (95%CI)	Significance
Age	35–39 years
40–44		1.05 (0.85, 1.30)	NS
45–49		0.88 (0.70, 1.10)	NS
50–54		0.68 (0.52, 0.88)	<0.01
55–59		0.66 (0.52, 0.83)	<0.01
Smoking	Current smoking	0.87 (0.75, 1.02)	NS
Drinking	Drink everyday	1.10 (0.94, 1.29)	NS
Sleep	Not recovered	0.34 (0.29, 0.40)	<0.001
Exercise	No habitual exercise	0.81 (0.69, 0.94)	<0.01
Breakfast	Less than 3 times/week	0.91 (0.76, 1.10)	NS
Night snacking	More than 3 times/week	0.60 (0.48, 0.76)	<0.001
Type of work	Day work
	Two-shift work	0.81 (0.69, 0.95)	<0.01
	Three-shift work	0.97 (0.70, 1.34)	NS

NS, not significant.

Discussion

In this study, HPI had a relationship with psychological wellbeing using GHQ12. As age was also related to HPI, the authors conducted ANOVA stratified by age. Except subjects aged 50–54, HPI was negatively associated with GHQ12. Decrease of GHQ12 was observed in subjects aged 50s from Table I, and HPI score of subjects aged 55–59 was significantly higher than those of subjects aged 35–39 or 40–44 in this study (data was not presented). The effect of age on HPI and GHQ12 seems complicated and further survey is needed.

There was a significant relationship between two-shift work and GHQ12 by logistic regression analysis, and two-shift workers showed psychological wellbeing. The total weekly working hours of the subjects was 40 h, and extra work was basically not permitted; however, we could not obtain more information about the work characteristics, activity levels, and other possible differences between the shift groups, that might help us to understand the results better. We agree that shift work is physiologically more stressful to humans than day work, but the psychological stress related to the type of job still needs to be clarified. There is a report that the effect of shift work on coronary heart disease may depend on the duration of shift work [12], the change in psychological distress or wellbeing was not surveyed simultaneously. But information on the duration of shift work as a working carrier seems important and it should be considered with caution.

The results of the multiple logistic regression analysis indicated that three of six lifestyles, such as satisfactory sleep, not frequent night snacking and regular exercise, were significantly related to the GHQ12 scores. There is a report that desirable dietary lifestyle was related to poor mental health, whereas habitual exercise was associated with lower depressive symptoms [13]. In our study, not frequent night snacking was significantly related to psychological wellbeing. Logically, recommended or desirable dietary lifestyle leads good mental health and good mental health would lead to improvement of dietary habits. There is also a report that depressive state is not related to habitual exercise [14], which is not in concordance with outcome by Simonsick [13]. Although GHQ12 is not a tool to detect depressive state, psychological wellbeing relates strongly to mental illness in our study.

Berkman and Breslow presented that each lifestyle-related health practice had different effect on health outcome [3], and our research presented that some of the lifestyles were significantly related to psychological wellbeing, which also agrees with the past research [15]. Ezoe and Morimoto reported the association between lifestyle and mental health status using GHQ 28-item version (GHQ28) [16]. They concluded that good health practices are associated with better mental health status, although sex deference definitely existed. As three sub-scales of GHQ28 showed decreasing trend as HPI increased, the relationship between lifestyle and health status is not limited in mental but also in somatic health.

There is a limitation that GHQ12 is determined by several determinants such as physical illness, unemployment, sex and familiar factor [17]. These factors should be adjusted to know the net relationship between lifestyle and psychological wellbeing.

In conclusion, good lifestyle was significantly associated with psychological wellbeing, although cause–effect relationship cannot conclude because of methodological limitation of the study. Sorensen et al. used 1-year interventional approach and there was a significant effect of exercise on total GHQ score (30-item version) [18]. As GHQ12 and six lifestyle-related items were included into self-administered questionnaire with annual health examination, interventional follow-up study is possible to improve psychological wellbeing.

Acknowledgements

We wish to express our appreciation to the study participants.