This study aimed to determine subgroups of the Azar cohort population based on lifestyle patterns using the LCA method and compare the incidence of hypertension in lifestyle behavior subgroups. Considering the behavioral differences between men and women in Iranian society,the two sexes were investigated separately. Women were classified into three separate classes based on lifestyle patterns: a healthy (low-risk) lifestyle (25.7%), a moderate-risk lifestyle (secondhand smoke exposure and poor sleep quality) (65.3%), and a high-risk lifestyle (9.0%). The high-risk lifestyle included obese individuals with secondhand smoke exposure and poor sleep quality/physical activity. Men were classified into seven distinct classes based on lifestyle patterns:class 1 (13.3%) included smokers; class 2 (29.3%) included men with poor sleep quality;class 3 (16.3%) featured smokers with poor sleep quality; class 4 (23.1%) included people with poor sleep quality and physical activity;class 5 (5.7%) included ex-smokers exposed to secondhand smoke with poor sleep quality; class 6 (8.7%) included smokers and alcohol consumers with poor sleep quality; and class 7 (3.6%) included obese smokers with alcohol consumption, secondhand smoke exposure, and poor physical activity.
In the present study, the frequency of smoking, alcohol consumption, and substance use was higher among men than women, in line with Moradinazar et al. (21). Similarly, Shen et al. recorded a higher prevalence of smoking and alcohol consumption inmenthan in women (26). On the other hand, in agreement with the findings of Ghanbari et al., we found obesity and poor physical activity to be more common among women than men (27).
In the present study, the highest prevalence and incidence of hypertension in the female model was related to the high-risk class (class 3). Zhang et al.demonstrated an association between secondhand smoke exposure and hypertension risk(28). Also, a study linked secondhand smoke exposure with hypertension among non-smokers (OR=1.16) (29). On the other hand, previous studies have shown that both short and long sleep durations are related to an increased risk of hypertension in most age groups (30, 31). Ewunieet al.concluded that sedentary adults are 2.55 times more likely to suffer from hypertension than physically active adults(32). According toWenzhen Li et al.,the combined effect of low physical activity and high BMI is associated with the highest risk of hypertension (33). Obesity is one of the most critical determinants of hypertension. The chance of having hypertension in obese adults is two(34)to three(33) times higher compared to those with normal BMI. Misuzu Fujita et al.demonstrated a stronger effect of obesity on the incidence of hypertension in women than in men (35). In the present study, women in the high-risk class accumulated all these risk factors, increasing the prevalence and incidence of hypertension.
In the male model, the highest prevalence (23.4%) and incidence (17.8%) of hypertension were related to class 4 (poor physical activity and sleep quality). This class included almost a quarter of all men (23.1%), reflecting the necessity of paying more attention to this group. In this class, the incidence and prevalence of hypertension were significantly greater compared with class 3 (smokers with poor sleep quality). As poor sleep quality was present in both classes, these differences are most likely related to the effect of physical activity. On the other hand, the comparison of class 1 (smokers) with class 3 (smokers with poor sleep quality) showed that the addition of sleep problems led to an increase in the incidence and prevalence of hypertension. These two influential factors, i.e., poor physical activity and poor sleep quality, were aggregated in class 4. According to Belinda Hernández et al., poor sleep quality and physical activity are associated with a higher risk of chronic diseases, including hypertension(36). Yongbin Li et al. showed a significant correlation between physical activity and sleep (37). Merellano-Navarro et al. found that being a man and having appropriate physical activity improves sleep quality regardless of age (38). Also, one review concluded that moderate physical activity affects sleep quality more than intense physical activity in all age groups (39). Therefore, through interventions that increase physical activity, sleep quality can also be improved, theoretically reducing the incidence of hypertension in high-risk groups.
After class 4, the highest incidence and prevalence of hypertension was related to class 7 (obese smokers with alcohol consumption, secondhand smoke exposure, and poor physical activity). A problematic behavior common to both these classes is poor physical activity. In 2018, the Physical Activity Guidelines Advisory Committee provided strong evidence on the protective effect of physical activity against hypertension based on a meta-analysis of 15 clinical trials (40). Also, the inverse relationship between physical activity and hypertension has been reported in different countries (Britain, China, Denmark, France, Italy, Korea, Saudi Arabia, and Thailand), consistent with our results (41, 42). A study compared physical activity with other lifestyle interventions (weight loss, diet modification, smoking cessation, and moderation of alcohol consumption) and showed that among the recommended lifestyle changes, increased physical activity had broad benefits (43). Another important reason for the high incidence and prevalence of hypertension in class 7 is obesity. In this regard, a study concluded that overweight and obesity are significant and independent risk factors for hypertension; this relationship was significant after adjusting for confounding factors such as age, gender, smoking, healthy diet, and physical activity(44). For every 3 kg/m2 increase in BMI, the risk of hypertension increases by 50% in men and 57% in women (45). Regular physical activity and weight control can reduce the risk of hypertension, and physical activity's protective effect remains the same in both sexes regardless of obesity levels (46).
Among men, by comparing class 2 (poor sleep quality) and class 3 (smokers with poor sleep quality), we found that the addition of smoking did not lead to an increase in the incidence of hypertension. Regarding the effect of smoking on blood pressure, prior studies have provided conflicting results. A meta-analysis showed no causal relationship between smoking and increased risk of hypertension; rather, smoking was associated with lower blood pressure and a decreased prevalence of hypertension (47). Smoking causes an acute and transient increase (about 15 minutes) in blood pressure (48). However, the chronic effect of smoking on hypertension is controversial (49). Another study showed that, only in older men, blood pressure was significantly higher in smokers than in non-smokers (50). Also, class 3 (smokers with poor sleep quality) featured a lower incidence and prevalence of hypertension than class 5 (ex-smokers with secondhand smoke exposure and poor sleep quality). In this regard, Guoju Li et al.revealed lower blood pressure levels in smokers than in non-smokers and ex-smokers (49). One explanation may be the lower BMIs in smokers and higher BMIs in ex-smokers(51) since a significant interaction exists between BMI, smoking, and blood pressure among men(50). However, these findings should not distract attention from the known harms of smoking (52). The inverse relationship between smoking and hypertension and the higher prevalence of hypertension in ex-smokers may be because doctors are more likely to advise people with hypertension to quit smoking. In fact, ex-smokers are more aware of their blood pressure than non-smokers, pushing them toward quitting (53). On the other hand, a cohort study showed that smoking cessation significantly reduces blood pressure (54). Nonetheless, smoking cessation was not mentioned as the best-proven lifestyle intervention in the 2017 guidelines on hypertension(40).
The incidence and prevalence of hypertension were lower in class 6 than in class 3. As the difference between these two classes was in the presence of alcohol consumption in class 6, our findings reflect a protective role of alcohol against the occurrence of hypertension. Similarly, Won Kim Cook et al. found a lower hypertension prevalence in smokers and alcohol consumers(55). A systematic review of 32 randomized controlled trials concluded that low and moderate doses of alcohol reduce blood pressure, while high doses have a biphasic effect on blood pressure, reducing it in the first 12 hours but increasing it after 13 hours(56). Naghipour et al.found no independent relationship between alcohol consumption or smoking and hypertension risk(16). Among white males, one study concluded that large amounts of alcohol are an independent risk factor for hypertension, but low to moderate alcohol consumption is not associated with a higher incidence of hypertension (57). Min-GyuYoo et al. linked moderate and heavy alcohol consumption with the risk of hypertension in men (58). In our study, the classification of alcohol consumption was such that people who had ever experienced alcohol consumption were considered as part of the "yes" answer, which includes a large share of alcoholics. Therefore, the lower incidence and prevalence of hypertension in class 6may be related to the roles of alcohol and smoking.
Strengths andlimitations
We ran LCA models for women and men separately to maximize statistical power since risky lifestyle behaviors follow different patterns between the sexes. The large sample size and the use of information from five follow-up periods were also among the study's strengths. However, this study also had limitations. As the age at entry into the study was 35-70 years, comparisons with studies conducted on adults of all ages might be limited. Furthermore, the level of smoking, alcohol consumption, and secondhand smoke exposure was not considered.