Similarities and differences in the transition of HRB cluster members between China and Japan

We found that most of the members of the HRB clusters remained stable across the two countries over time. This finding was consistent with evidence from previous studies in the United States of America (Burgard et al., Reference Burgard, Lin, Segal, Elliott and Seelye2018), the United Kingdom (Mawditt et al., Reference Mawditt, Sacker, Britton, Kelly and Cable2019) and Taiwan (Hsu et al., Reference Hsu, Luh, Chang and Pan2013). Another trajectory study of a single health-impairing behaviour found that HRBs appeared to remain stable much earlier in the lifecourse (adolescence to young adulthood) (Nora et al., Reference Nora, Kyrre and Bente2015). This may be a hint that preventive interventions for HRBs need to be carried out earlier in the population to promote a good lifestyle which may otherwise be difficult to change in the future.

Nevertheless, the cross-country difference was that in China, the probability of maintaining an unhealthy lifestyle pattern was more than 95 per cent, while a relatively low percentage of people were able to maintain a healthy lifestyle pattern. In contrast, in Japan, the probability of maintaining a healthy lifestyle pattern was 99 per cent, and a minority (3%) of people with unhealthy lifestyle patterns also tended to become healthier over time. This improvement in HRBs in Japan may be linked to the Japanese government's lifestyle intervention programme. All health insurance companies in Japan have been required since 2008 to provide health checkups and health guidance to those aged 40–74 years at higher risk of lifestyle-related diseases, to encourage behavioural change towards a healthier lifestyle (Kohro et al., Reference Kohro, Furui, Mitsutake, Fujii, Morita, Oku, Ohe and Nagai2008). A three-year follow-up of the programme found that participants showed greater and steady improvements in metabolic syndrome risk factors, such as waist circumference, body weight and BMI (Tsushita et al., Reference Tsushita, S, Miura, Ito, Fukuda, Kitamura and Tatara2018). Although China has also been conducting ‘China Healthy Lifestyle for All’ since 2007, this universal health education-based initiative has been found to improve knowledge and awareness of healthy lifestyles, but the long-term effects on improving health behaviours have yet to be evaluated further (Yuan et al., Reference Yuan, Juan, Xiao-ming and Xiao-feng2013). This suggests that further policy measures may be needed in China to promote improvements in HRBs among those at high risk of lifestyle diseases.

Another difference we found in the transitions in HRB clustering memberships between the two countries was the occurrence of smoking cessation among the Japanese study population. Between each wave of the JSTAR cohort, there was a transition from the ‘current smoking and drinking’ cluster to the ‘ex-smoking and drinking’ cluster, indicating that over time this group of Japanese people began to quit smoking. This also demonstrated an improvement in health-risk behaviours among middle-aged and older adults in Japan, and is consistent with evidence from studies of single health behaviours, such as the declining prevalence of smoking in Japan (Ministry of Health, Labour and Welfare, 2020). Such changes may be related to the tobacco control measures taken by the Japanese government (Goto et al., Reference Goto, Takahashi and Ida2011), the increase in the price of cigarettes (Matsubayashi et al., Reference Matsubayashi, Tabuchi and Iso2021), the increase in public awareness of the dangers of smoking and possibly changes brought about by the development of age-related non-communicable diseases (Stelmach et al., Reference Stelmach, Kaczmarczyk-Chałas, Bielecki and Drygas2004). Furthermore, in Japan, smoking cessation treatment has been included in health insurance since 2006 (Li et al., Reference Li, Okamoto and Shirai2019). In China, however, we did not find a cluster characterised by ex-smoking, which may be related to the low cessation rate in China (less than 10%), although the study found an increasing number of smokers who stopped smoking, rising from 3 per cent in 1991 to 9 per cent in 2006 (Chen et al., Reference Chen, Peto, Zhou, Iona, Smith, Yang, Guo, Chen, Bian, Lancaster, Sherliker, Pang, Wang, Su, Wu, Wu, Chen, Collins and Li2015). Therefore, our study could not identify smoking cessation among Chinese smokers, but we found a transition from the ‘healthy lifestyle’ group to the ‘smoking’ group, who started smoking over time. This may be related to changes in their marital status, as we found more separations/divorces/widowhoods in the second and third waves of the ‘smoking’ cluster, and some studies have found lower smoking rates among married men (Lindström, Reference Lindström2010).

Similarities and differences in the sociodemographics of HRB cluster members in China and Japan

Using multiple regression models, we found that the smoking and drinking alcohol populations in China and Japan possessed similar sociodemographic characteristics. Our findings are consistent with existing evidence that smoking and alcohol consumption are more likely to occur in men, in those with low levels of education and in those who are unmarried or divorced (Cho et al., Reference Cho, Khang, Jun and Kawachi2008; Lindström, Reference Lindström2010). Moreover, our findings also indicate that participants aged 60 years and above were likely to have more positive HRBs than those aged 50–60, in line with findings reported previously (Schneider et al., Reference Schneider, Huy, Schuessler, Diehl and Schwarz2009; Morris et al., Reference Morris, D'Este, Sargent-Cox and Anstey2016). This may be related to changes in HRBs associated with retirement (the official retirement age was 60 for men and 55 for women in China, and 65 in Japan), such that retired people would have increased time and frequency of outdoor activity (Sjösten et al., Reference Sjösten, Kivimäki, Singh-Manoux, Ferrie, Goldberg, Zins, Pentti, Westerlund and Vahtera2012; Syse et al., Reference Syse, Veenstra, Furunes, Mykletun and Solem2017), as well as reduced alcohol consumption and smoking due to fewer work-related social engagements (Liao et al., Reference Liao, Mawditt, Scholes, Lu and Mejía2019; Yan et al., Reference Yan, Xiang, Meng, Liang and Yue2022).

We also found differences in gender and socioeconomic statuses of the ‘overweight or obese’ cluster across the two countries, with more females and higher income in China and the opposite in Japan. The variation in gender that we found is consistent with evidence from studies of obesity alone. In China, the prevalence of obesity is significantly higher among women than men (Wang et al., Reference Wang, Wang and Li2001), while in Japan the opposite was true (Nakamura et al., Reference Nakamura, Nakamura, Saitoh, Okamura, Yanagita, Yoshita, Nishi, Okuda, Kadota, Ohkubo, Ueshima, Okayama and Miura2018). Although the political and cultural backgrounds of both countries are strongly influenced by Confucianism, differences in stages of socioeconomic development and social perceptions may be able to explain the differences in socioeconomic status of the ‘overweight or obese’ cluster (Dinsa et al., Reference Dinsa, Goryakin, Fumagalli and Suhrcke2012). For example, in a developing country like China (Noh et al., Reference Noh, Kim, Yang, Park, Cheon and Kwon2017; The World Bank, 2019), where overweight and obesity are more often seen as symbols of wealth and health, there is greater social tolerance of overweight (Noh et al., Reference Noh, Kim, Yang, Park, Cheon and Kwon2017). Low socioeconomic status groups are more likely to adopt affordable lifestyles such as low- to moderate-intake diets and higher physical activity, and higher socioeconomic status groups are more likely to adopt high-fat and high-sugar diets and less physical activity due to more options, leading to nutritional non-communicable diseases (e.g. obesity) being more prevalent (Kim et al., Reference Kim, Symons and Popkin2004; Bai et al., Reference Bai, Wu, Dong, Liu, Yang and Lyu2020). Whereas Japan is a high-income developed country (The World Bank, 2019) that is heavily influenced by Western culture (Noh et al., Reference Noh, Kim, Yang, Park, Cheon and Kwon2017), and people have become accustomed to unhealthy eating patterns. Moreover, there is a greater social stigma attached to obesity (Noh et al., Reference Noh, Kim, Yang, Park, Cheon and Kwon2017), and so higher socioeconomic groups are able to make more-considered choices about healthier lifestyles (Nakamura et al., Reference Nakamura, Inayama, Hata, Matsushita, Takahashi, Harada and Arao2016).

The strength of this study lies in the use of comparable nationally representative ageing cohorts from China and Japan to provide additional information on the clustering of HRBs and related sociodemographic characteristics in both countries. This study was expanded to include the 50–65-year-old population compared to the more focused 65+ study. Moreover, longitudinal research allows us to investigate changes in HRB cluster membership over time in each cohort. To contribute to the evidence of change in the clustering of HRBs over time in an Asian elderly population, we applied LTA, a powerful method that considers the interrelationships between multiple HRBs, to identify information on changes in HRB clusters over time. However, there are some limitations to this study. First, measures of HRBs were self-report and respondents may tend to be more likely to underestimate health-damaging behaviours in an attempt to respond in a socially desirable manner (Ferrari et al., Reference Ferrari, Werneck, Silva, Kovalskys, Gómez, Rigotti, Cortés, García, Liria, Herrera-Cuenca, Zimberg, Guajardo, Pratt, Cristi-Montero, Marques, Peralta, Bolados, Leme, Rollo and Fisberg2021). Second, the present study was constrained to the variables and measures available; we were not able to completely harmonise HRB and sociodemographic variables (e.g. physical activity and urban/rural) across the two cohorts, nor could we cover all HRBs, but the ‘SNAP’ risk factors covered common and critical health-related modifiable factors (The Royal Australian College of General Practitioners, 2004). Similarly, restricted by harmonised variables comparable across the two cohorts, this study can only make relatively broad categories of smoking, alcohol consumption and physical activity, and use BMI instead of diet (Campostrini and McQueen, Reference Campostrini, McQueen, McQueen and Puska2003). Future cross-national studies would benefit from more co-ordinated and detailed measures of lifestyle activities. Third, the dates we used differed in the time periods, so participants in both cohorts at the same age would have lived in different conditions early in their lifecourse due to differences in social context (e.g. policies, economic and social development, etc.) (Lei et al., Reference Lei, Jiaxin and Qiang2021), thus affecting their current HRBs and limiting comparisons between the same period in China and Japan. However, it also showed the improvement of HRBs in Japan at an earlier time. Finally, the current study only compared the clustering of HRBs and associated sociodemographic characteristics in middle-aged and older adults in China and Japan, without taking health status into consideration. We intend to extend this work by exploring the bidirectional association between HRB cluster membership and health outcomes in the future.

In conclusion, this study found that, in both China and Japan, the clustering profiles of HRBs were highly consistent with several clusters of multiple unhealthy behaviours identified in previous studies, and that people with specific sociodemographic backgrounds were more likely to be in these clusters. These findings could help facilitate the design of targeted multi-behavioural health interventions to promote healthy lifestyles among older adults in both countries. We also found that the majority of HRB cluster members remained stable over time. However, a minority of members in Japan were more inclined to transition to healthier lifestyles, while the opposite was true in China, especially among the overweight or obese and smoking populations. Despite the measures taken by both governments, the positive improvements in BMI and smoking among middle-aged and older adults in Japan could suggest that China can gain insights and experiences from neighbouring Japan and develop nationally appropriate health behaviour promotion policies.