背景与目的 长时间久坐已被证实与全因死亡及心血管疾病（Cardiovascular Disease, CVD）风险增加相关，但其在不同职业人群中的差异尚不明确。本研究旨在基于前瞻性城乡流行病学（Prospective Urban Rural Epidemiological study, PURE）中国地区队列研究，探讨中国体力劳动职业人群与非体力劳动职业人群中久坐时间与全因死亡及CVD风险之间的关联差异。

方法 本研究依托PURE China队列研究，在2005年至2009年间在中国12个省份115个社区招募47,931名年龄在35至70岁之间的参与者。久坐时间采用国际体力活动问卷（International Physical Activity Questionnaire, IPAQ）测量。研究的主要结局为全因死亡和主要不良心血管事件（定义为心血管死亡、非致死性心肌梗死、卒中或心力衰竭）。参与者的职业信息通过标准化问卷收集，并依据2008年国际职业分类标准（International Standard Classification of Occupations, ISCO-08）和意大利国家统计研究所2001年职业分类标准（Italian National Institute of Statistics 2001, ISTAT-2001）划分为体力劳动职业与非体力劳动职业。将参与者按基线日均久坐时长分为4组：0 - 4、4 - 6、6 - 8、≥8小时/天。采用多因素Cox共享脆弱模型分析久坐时间与全因死亡和CVD风险的关联，并比较在不同性别、年龄和城乡中的关联差异。采用限制性立方样条模型拟合久坐时长与死亡风险及CVD风险的剂量效应关系。最后进行敏感性分析验证结果的稳定性。

结果 经过剔除数据缺失及基线时患有CVD的参与者后，最终43,256名纳入分析，其中男性占41.6%（n= 18,004），平均年龄为50.6 ± 9.5岁。在随访11.9 ± 3.0年期间，共记录2,271例参与者发生全因死亡事件，3,408例参与者发生主要不良心血管事件。根据ISCO-08和ISTAT-2001职业分类标准，35,294名参与者（81.6%）属于体力劳动职业，而7,962名参与者（18.4%）属于非体力劳动职业。多因素Cox共享脆弱模型表明，在体力劳动职业人群中，相较于久坐小于4 h的人群，久坐时间6 - 8 h全因死亡风险平均增加30%（HR = 1.30, 95%CI: 1.10 - 1.53），主要不良心血管事件风险平均增加18%（HR = 1.18, 95%CI: 1.03 - 1.35）；久坐时间8 h以上全因死亡风险平均增加52%（HR = 1.52, 95%CI: 1.14 - 2.02），主要不良心血管事件风险平均增加40%（HR = 1.40, 95%CI: 1.09 - 1.78）。在分别分析CVD死亡风险和发病风险时，亦观察到相似趋势。在男性、年龄50岁及以上、农村地区人群中这种关联更加明显。限制性立方样条模型显示，久坐时间与全因死亡及主要不良心血管事件风险之间存在明显的非线性剂量-反应关系，当久坐时间＞8小时/天，随着久坐时间的增加，发生全因死亡及主要不良心血管事件的风险显著增加。在非体力劳动职业人群中，相较于久坐小于4 h的人群，久坐时间8 h以上主要不良心血管事件风险平均增加88%（HR = 1.88, 95%CI: 1.19 - 2.98）。在分别分析CVD死亡风险和发病风险时，亦观察到相似趋势。在男性、年龄50岁以下、城市地区人群中这种关联更加明显。敏感性分析结果显示，本研究的主要研究结果均较稳定。

结论 本研究表明，长时间久坐与中国成年人全因死亡及CVD风险显著增加相关。在体力劳动者中，久坐时间超过6小时/天显著增加全因死亡和CVD风险；在非体力劳动者中，久坐时间超过8小时/天显著增加CVD风险。研究结果提示，应针对不同职业人群制定个性化的干预措施，以减少久坐行为对健康的不良影响。

Background and Objective
Prolonged sitting has been shown to be associated with an increased risk of all-cause mortality and cardiovascular disease (CVD). However, whether this association varies across occupational groups remains unclear. Given the differences in working environments, activity patterns, and health conditions between manual and non-manual occupations, it is crucial to explore the impact of sedentary behavior on the health of different occupational groups. This study aimed to investigate the association between sitting time and the risk of all-cause mortality and CVD in manual and non-manual workers in China based on the Prospective Urban and Rural Epidemiological (PURE) China cohort.

Methods
This study was based on the PURE China cohort study. Between 2005 and 2009, a total of 47,931 participants aged 35 to 70 years were recruited from 115 communities across 12 provinces in China. Sitting time was assessed using the International Physical Activity Questionnaire (IPAQ). The primary outcomes were all-cause mortality and major adverse cardiovascular events (defined as cardiovascular death, cardiovascular incidence). Occupational information was collected using standardized questionnaires and classified as manual or non-manual occupations according to the 2008 International Standard Classification of Occupations (ISCO-08) and Italian National Institute of Statistics 2001 (ISTAT-2001) occupational classification system. Participants were categorized into four groups based on their daily sitting time at baseline: 0 - 4, 4 - 6, 6 - 8, and ≥8 hours/day. A multivariable Cox shared frailty model was used to examine the association between sitting time and the risk of all-cause mortality and CVD, and to assess differences across sex, age, and urban-rural subgroups. A restricted cubic spline model was applied to explore the dose-response relationship between sitting time and the risk of all-cause mortality and CVD. Sensitivity analyses were performed to verify the robustness of the results.

Results
After excluding participants with missing data and those with pre-existing CVD at baseline, 43,256 participants were included in the final analysis, of whom 41.6% were men (n = 18,004), with a mean age of 50.6 ± 9.5 years. During a follow-up period of 11.9 ± 3.0 years, 2,271 participants experienced all-cause mortality events, and 3,408 participants experienced major adverse cardiovascular events. According to the ISCO-08 and ISTAT-2001 occupational classification system, 35,294 participants (81.6%) were classified as manual workers, and 7,962 participants (18.4%) as non-manual workers.

In the multivariable Cox shared frailty model, among manual workers, compared with those who sat for less than 4 hours/day, participants with 6–8 hours/day of sitting had a 30% higher risk of all-cause mortality (HR = 1.30, 95% CI: 1.10 - 1.53) and an 18% higher risk of major adverse cardiovascular events (HR = 1.18, 95% CI: 1.03 - 1.35). Those who sat for ≥8 hours/day had a 52% higher risk of all-cause mortality (HR = 1.52, 95% CI: 1.14 - 2.02) and a 40% higher risk of major adverse cardiovascular events (HR = 1.40, 95% CI: 1.09 - 1.78). Similar trends were observed when CVD mortality and incidence were analyzed separately. The association was more pronounced among men, individuals aged ≥50 years, and those in rural areas.

The restricted cubic spline model showed a significant nonlinear dose-response relationship between sitting time and the risk of both all-cause mortality and major adverse cardiovascular events. When sitting time exceeded 8 hours/day, the risk of all-cause mortality and major adverse cardiovascular events increased significantly with prolonged sitting.

Among non-manual workers, participants who sat for ≥8 hours/day had an 88% higher risk of major adverse cardiovascular events compared with those who sat for less than 4 hours/day (HR = 1.88, 95% CI: 1.19 - 2.98). Similar trends were observed when CVD mortality and incidence were analyzed separately. This association was more pronounced among men, individuals aged <50 years, and those in urban areas. Sensitivity analyses confirmed the robustness of the main findings.

Conclusion
This study indicates that prolonged sitting time is significantly associated with an increased risk of all-cause mortality and CVD in Chinese adults. Among manual workers, sitting for more than 6 hours/day was associated with significantly higher risks of all-cause mortality and CVD, while among non-manual workers, sitting for more than 8 hours/day significantly increased the risk of CVD. These findings highlight the need for tailored interventions targeting different occupational groups to mitigate the adverse health effects of prolonged sitting.