Abstract
目的
探讨体重校正腰围指数(weight-adjusted waist index，WWI)与美国成人急性、亚急性、慢性疼痛之间的相关性。
方法
采用横断面研究，提取1999—2004年美国国家卫生和营养检查调查(National Health and Nutrition Examination Survey，NHANES)数据库中关于成人腰围、体质量和疼痛等变量，及性别、年龄、种族、婚姻状况、教育水平、家庭收入、体力活动情况、饮酒、吸烟和糖尿病患病状况等协变量数据。采用多分类Logistic回归分析构建3种模型，评估WWI与急性、亚急性和慢性疼痛之间的相关性。模型1未对协变量进行校正，模型2对年龄、性别、种族、婚姻状况、教育水平和家庭收入情况进行校正，模型3进一步校正了体力活动、饮酒、吸烟和糖尿病患病情况等所有协变量。
结果
共纳入12 694例参与者，平均年龄为(50.8±18.7)岁, 其中9 614例(75.74%)未出现超过24 h的疼痛，870例(6.85%)出现急性疼痛，354例(2.79%)出现亚急性疼痛，1 856例(14.62%)出现慢性疼痛。所有参与者的WWI为(10.95±0.85) cm/
，根据WWI的四分位数分为4组：Q1组为(7.90~10.36) cm/
，Q2组为(10.37~10.94) cm/
，Q3组为(10.95~11.53) cm/
，Q4组为(11.54~15.20) cm/
。随着WWI的增加，参与者的急性、慢性疼痛状态的差异有统计学意义(P < 0.001)。模型1中，与Q1组相比，Q2组和Q4组的急性疼痛风险降低(Q2组：OR=0.765，95%CI：0.615~0.953，P=0.017；Q4组：OR=0.648，95%CI：0.503~0.835，P < 0.001)；与Q1组相比，Q2组、Q3组和Q4组的慢性疼痛风险均增加(Q2组：OR=1.365，95%CI：1.149~1.622，P < 0.001；Q3组：OR=1.291，95%CI：1.082~1.541，P=0.005；Q4组：OR=1.874，95%CI：1.579~ 2.224，P < 0.001)。模型2中，与Q1组相比，其他3组慢性疼痛风险增加(Q2组：OR=1.359，95%CI：1.137~1.624，P=0.001；Q3组：OR=1.260，95%CI：1.039~1.528，P=0.019；Q4组：OR=1.735，95%CI：1.413~2.132，P < 0.001)。模型3中与Q1组相比，Q4组的慢性疼痛风险增加49.2%(OR=1.492，95%CI：1.208~1.842，P < 0.001)。在模型2和模型3中，急性疼痛与WWI未见相关性(均P>0.05)；3个模型均未发现亚急性疼痛与WWI存在相关性(均P>0.05)。
结论
WWI与美国成人急性疼痛、亚急性疼痛之间未见明显相关性，但随着WWI的增加，慢性疼痛风险增加, 所以有必要通过大规模前瞻性研究进一步验证这一结论。
Keywords: 疼痛, 体重校正腰围指数, 肥胖, 横断面研究
Abstract
Objective
To investigate the relationship between the weight-adjusted waist index (WWI) and acute, subacute pain or chronic pain among American adults.
Methods
There was a cross-sectional study. Data from the 1999-2004 National Health and Nutrition Examination Survey (NHANES) concerning waist circumference, weight, pain status and covariates (age, gender, race, marital status, education level and income, physical activity, alcohol consumption, smoking status, and diabetes) were extracted for analysis. Multinomial Logistic regression was conducted across the three models to investigate the associations between WWI and acute, subacute and chronic pain. Model 1 did not involve any adjustments. Model 2 involved adjustments for age, gender, race, marital status, education level, and income. Model 3 was further adjusted for physical activity, alcohol consumption, smoking, and diabetes status.
Results
This study involved 12 694 participants with an average age of (50.6±18.7) years. Among all the participants, 9 614 people (75.74%) had no pain, 870 people (6.85%) experienced acute pain, 354 people (2.79%) suffered from subacute pain, and 1 856 people (14.62%) experienced chronic pain. The WWI of all the participants was (10.95±0.85) cm/
, divided into four groups based on quartiles: Group Q1 (7.90-10.36) cm/
, group Q2 (10.37-10.94) cm/
, group Q3 (10.95-11.53) cm/
and group Q4 (11.54-15.20) cm/
. With the increase of WWI, the analysis revealed a significant statistical difference in the participants' acute and chronic pain status (all P < 0.001). In Model 1, the prevalence of acute pain was lower in group Q2 and group Q4 compared with group Q1 (group Q2: OR=0.765, 95%CI: 0.615-0.953, P=0.017; group Q4: OR= 0.648, 95%CI: 0.503-0.835, P < 0.001). Compared with group Q1, the prevalence of chronic pain increased in group Q2, group Q3, and group Q4 (group Q2: OR =1.365, 95%CI: 1.149-1.622, P < 0.001; group Q3: OR=1.291, 95%CI: 1.082-1.541, P=0.005; group Q4: OR=1.874, 95%CI: 1.579-2.224, P < 0.001). In Model 2, compared with group Q1, an increase in chronic pain prevalence was still associated with an increase in WWI in other three groups (group Q2: OR=1.359, 95%CI: 1.137-1.624, P=0.001; group Q3: OR=1.260, 95%CI: 1.039-1.528, P=0.019; group Q4: OR=1.735, 95%CI: 1.413-2.132, P < 0.001). In Model 3, group Q4 had a 49.2% increased prevalence of chronic pain compared to group Q1 (OR = 1.492, 95%CI: 1.208-1.842, P < 0.001). However, in Models 2 and 3, no significant relationship was observed between acute pain and WWI (all P>0.05). And none of the three models identified a significant association between subacute pain and WWI (all P>0.05).
Conclusion
For American adults, there was no significant correlation between WWI and acute pain or subacute pain. However, as WWI increases, so does the prevalence of chronic pain. Further validation of this conclusion through large-scale prospective studies is warranted.
Keywords: Pain, Weight-adjusted waist index, Obesity, Cross-sectional study
疼痛是一种与实际或潜在组织损伤相关或类似的不愉快感觉和情感体验[1]。研究表明，疼痛是患者就医的最常见原因，约五分之一的门诊患者的主要症状或诊断是疼痛，而11.2% 的成年人报告每天都有疼痛症状，这给个人和医疗保健系统带来沉重的负担[2-3]。疼痛涉及复杂的生理、心理和社会因素的相互作用，其中肥胖与疼痛的共患病关系成为越来越多研究的重点[4]。一方面肥胖导致过度的机械负荷和促炎状态可能使得机体的疼痛阈值降低，而慢性疼痛患者更容易出现超重、肥胖，甚至代谢综合征[5]；另一方面，针对肥胖和慢性疼痛的综合跨学科治疗，如通过饮食干预减轻体质量，可更有效地改善疼痛症状，这表明监测和干预肥胖对于疼痛患者具有临床意义[6]。
临床和流行病学研究中，定义肥胖的最常用指标是体重指数(body mass index，BMI)[7]。然而，BMI不能反映全身脂肪量或中心性肥胖，而中心性肥胖与疼痛具有更强的独立相关性[8]。体重校正腰围指数(weight-adjusted waist index，WWI)是一种新型肥胖指标，主要评估中心性肥胖，并与脂肪量呈正相关[9]。研究表明，WWI与抑郁症、认知功能障碍和心血管疾病有更强的相关性[10-12]。然而，WWI与疼痛状态之间的关系尚不清楚，因此，本研究依据美国国家卫生和营养检查调查(National Health and Nutrition Examination Survey，NHANES)的数据，评估WWI与疼痛的相关性，以进一步改善疼痛防治策略。
1. 资料与方法
1.1. 数据来源和研究人群
本研究是应用NHANES调查数据的横断面研究。NHANES是一项旨在评估美国成人和儿童健康和营养状况的研究项目，采用严格的多阶段概率抽样方法以确保代表性。该方案经美国国家卫生统计中心(National Center for Health Statistics，NCHS)研究伦理审查委员会批准，知情同意书由NHANES研究方案的所有参与者签署。有关NHANES调查的更多详细信息，可访问 https://www.cdc.gov/nchs/nhanes/index.htm。
由于NHANES仅在1999— 2004年提供了关于疼痛状态的问卷，且提问仅限于20岁以上成人，因此，本研究收集了以上3个NHANES周期，共计31 126名参与者的数据，排除缺乏体质量或腰围数据的5 502例、缺乏疼痛相关信息的12 200例和自我报告怀孕的730例后，最终12 694例参与者进行了后续分析。
1.2. 疼痛的定义
本研究中，确认参与者疼痛状态的依据是杂项疼痛问卷。过去1个月内没有持续时间超过24 h疼痛定义为无疼痛；疼痛持续时间超过24 h但不到1个月定义为急性疼痛；疼痛持续时间超过1个月但不到3个月定义为亚急性疼痛；疼痛持续时间超过3个月定义为慢性疼痛。所有参与者按此定义分为无疼痛、急性疼痛、亚急性疼痛和慢性疼痛4组。
1.3. WWI的计算
WWI评分是一个与中心性肥胖呈正相关的新型指标，计算方法是参与者的腰围(单位为cm)除以体质量(单位为kg)的平方根，四舍五入到小数点后两位。本研究中，WWI为暴露变量，是一个连续变量，然后根据WWI的四分位数将参与者分为Q1组、Q2组、Q3组和Q4组进行分析。
1.4. 协变量
根据文献[3, 13]和临床经验，本研究的协变量包括性别、年龄、种族、婚姻状况、教育水平、家庭收入、体力活动、吸烟、饮酒和糖尿病患病情况。
1.5. 统计学分析
运用EmpowerStats 2.0进行数据整理，应用SPSS 25.0和Stata 17.0软件进行统计学分析。根据NHANES的建议，本研究中的所有分析均采用加权方案计算。分类变量以频率和百分比表示，连续变量以 ±s 表示。连续变量应用单因素ANOVA检验、分类变量应用卡方检验来分析疼痛4组的基本特征。采用多分类Logistic回归法分析WWI的四分位数4组与急、慢性疼痛的相关性。模型1未进行任何校正，模型2校正了年龄、性别、种族、婚姻状况、教育水平和家庭收入协变量；模型3进一步校正了体力活动、饮酒、吸烟状况和糖尿病患病情况。P < 0.05认为差异有统计学意义。
2. 结果
2.1. 参与者的特征
本研究纳入12 694例参与者，平均年龄为(50.6±18.7)岁，其中6 585例(50.3%)为男性，6 309例(49.7%)为女性。所有参与者中，9 614例(75.74%)未出现超过24 h的疼痛，870例(6.85%)出现急性疼痛，354例(2.79%)出现亚急性疼痛，1 856例(14.62%)出现慢性疼痛。无疼痛、急性疼痛、亚急性疼痛、慢性疼痛4组在WWI、人口学数据、生活习惯和糖尿病患病情况均差异有统计学意义(均P < 0.001)，见表 1。
表 1.
4组疼痛状态参与者的比较
Characteristics of participants of four groups with different pain status
| Items | No pain (n=9 614) |
Acute pain (n=870) |
Subacute pain (n=354) |
Chronic pain (n=1 856) |
F/χ2 | P |
| WWI, weight-adjusted waist index. PIR, poverty income ratio. | ||||||
| WWI/(cm/kg), x±s | 10.76±0.81 | 10.67±0.78 | 10.76±0.80 | 10.94±0.82 | 23.593 | < 0.001 |
| Age/years, n (%) | 218.748 | < 0.001 | ||||
| < 40 | 3 206 (33.3) | 369 (42.4) | 110 (31.1) | 437 (23.5) | ||
| 40-59 | 2 791 (29.0) | 320 (36.8) | 148 (41.8) | 727 (39.2) | ||
| ≥60 | 3 617 (37.7) | 181 (20.8) | 96 (27.1) | 692 (37.3) | ||
| Gender, n (%) | 53.730 | < 0.001 | ||||
| Male | 4 990 (51.9) | 435 (50) | 141 (39.8) | 819 (44.1) | ||
| Female | 4 624 (48.1) | 435 (50) | 213 (60.2) | 1 037 (55.9) | ||
| Race, n (%) | 129.162 | < 0.001 | ||||
| Non-hispanic whites | 4 619 (48.0) | 498 (57.2) | 195 (55.1) | 1 110 (59.8) | ||
| Non-hispanic blacks | 1 917 (19.9) | 158 (18.2) | 67 (18.9) | 348 (18.8) | ||
| Mexican Americans | 2 351 (24.5) | 151 (17.4) | 69 (19.5) | 287 (15.4) | ||
| Other racial backgrounds | 727 (7.6) | 63 (7.2) | 23 (6.5) | 111 (6.0) | ||
| Education level, n (%) | 32.430 | < 0.001 | ||||
| Less than high school | 1 917 (19.9) | 163 (18.7) | 67 (19.0) | 427 (23.0) | ||
| High school | 2 482 (25.9) | 212 (24.4) | 92 (25.9) | 533 (28.7) | ||
| Above high school | 5 195 (54.0) | 495 (56.9) | 195 (55.1) | 895 (48.2) | ||
| Missing | 20 (0.2) | 0 (0.0) | 0 (0.0) | 1 (0.1) | ||
| Marital status, n (%) | 62.155 | < 0.001 | ||||
| Married or living with a partner | 6 088 (63.3) | 558 (64.1) | 211 (59.6) | 1 255 (67.6) | ||
| Widowed or divorced or separated | 1 679 (17.5) | 147 (16.9) | 78 (22.1) | 396 (21.3) | ||
| Never married | 1 842 (19.2) | 165 (19.0) | 65 (18.3) | 204 (11.0) | ||
| Missing | 5 (0.0) | 0 (0.0) | 0 (0.0) | 1 (0.1) | ||
| PIR, n (%) | 48.824 | < 0.001 | ||||
| <1.0 | 1 251 (13.0) | 108 (12.4) | 59 (16.7) | 312 (16.8) | ||
| 1.0-2.9 | 3 500 (36.4) | 298 (34.2) | 126 (35.6) | 721 (38.8) | ||
| ≥ 3.0 | 4 863 (50.6) | 464 (53.4) | 169 (47.7) | 823 (44.4) | ||
| Daily physical activity, n (%) | 80.103 | < 0.001 | ||||
| Sedentary | 2 260 (23.5) | 199 (22.9) | 96 (27.1) | 575 (31.0) | ||
| Mild physical activity | 5 236 (54.5) | 426 (49.0) | 169 (47.7) | 910 (49.0) | ||
| Moderate physical activity | 1 454 (15.1) | 167 (19.2) | 54 (15.3) | 257 (13.8) | ||
| Severe physical activity | 655 (6.8) | 77 (8.8) | 35 (9.9) | 109 (5.9) | ||
| Missing | 9 (0.1) | 1 (0.1) | 0 (0.0) | 5 (0.3) | ||
| Smoking, n (%) | 112.445 | < 0.001 | ||||
| Never smokers | 5 052 (52.6) | 419 (48.2) | 173 (48.8) | 753 (40.5) | ||
| Former smokers | 2 009 (20.9) | 217 (24.9) | 93 (26.3) | 557 (30.0) | ||
| Current smokers | 2 539 (26.4) | 234 (26.9) | 88 (24.9) | 545 (29.4) | ||
| Missing | 14 (0.1) | 0 (0.0) | 0 (0.0) | 1 (0.1) | ||
| Alcoholic drinks per day, n (%) | 28.080 | < 0.001 | ||||
| No | 1 710 (17.8) | 148 (17.0) | 67 (18.9) | 489 (26.4) | ||
| 1-2 glasses | 2 685 (27.9) | 224 (25.7) | 85 (24.1) | 488 (26.3) | ||
| > 2 glasses | 5 219 (54.3) | 498 (57.3) | 202 (57.0) | 879 (47.3) | ||
| Diabetes, n (%) | 65.809 | < 0.001 | ||||
| No | 8 580 (89.2) | 794 (91.2) | 296 (83.6) | 1 561 (84.1) | ||
| Yes | 901 (9.4) | 71 (8.2) | 48 (13.6) | 261 (14.1) | ||
| Borderline | 130 (1.4) | 5 (0.6) | 9 (2.5) | 34 (1.8) | ||
| Missing | 3 (0.0) | 0 (0.0) | 1 (0.3) | 0 (0.0) | ||
所有参与者的平均WWI为(10.95±0.85) cm/
，并根据WWI的四分位数分为4组：Q1组为(7.90~10.36) cm/
；Q2组为(10.37~10.94) cm/
；Q3组为(10.95~11.53) cm/
；Q4组为(11.54~15.20) cm/
。
2.2. WWI与各类型疼痛的关系
采用加权无序多分类Logistic回归分析WWI与急性、亚急性和慢性疼痛的相关性，结果见表 2。模型1未校正任何协变量，与Q1组相比，Q2组和Q4组的急性疼痛患病率降低；与Q1组相比，Q2组、Q3组和Q4组的慢性疼痛风险均增加。在模型1中，亚急性疼痛与WWI未见明显相关性(均P>0.05)。模型2对协变量年龄、性别、种族、婚姻状况、教育水平和家庭收入进行校正后，与Q1组相比，Q2组、Q3组和Q4组的慢性疼痛风险增加。急性疼痛和亚急性疼痛均未见与WWI的相关性(均P>0.05)。模型3对所有协变量进行校正，发现与Q1组相比，Q4组的慢性疼痛风险增加49. 2%。
表 2.
体重校正腰围指数与疼痛关系的无序多分类Logistic回归分析
Multinomial Logistic analysis on the associations between weight-adjusted waist index and pain
| Type of pain | Model | Weight-adjusted waist index/(cm/ )(Q1 group as reference) |
|||||||
| Q2 | Q3 | Q4 | |||||||
| OR(95%CI) | P | OR(95%CI) | P | OR(95%CI) | P | ||||
| Model 1, no covariates were adjusted; Model 2, adjusted for age, gender, race, education level, marital status, and PIR; Model 3, adjusted for age, gender, race, education level, marital status, PIR, alcohol consumption, smoking, diabetes, and physical activity. PIR, poverty income ratio. | |||||||||
| Acute pain | Model 1 | 0.765 (0.615-0.953) | 0.017 | 0.880 (0.708-1.093) | 0.248 | 0.648 (0.503-0.835) | 0.001 | ||
| Model 2 | 0.873 (0.696-1.097) | 0.244 | 1.153 (0.910-1.460) | 0.239 | 0.974 (0.722-1.314) | 0.864 | |||
| Model 3 | 0.875 (0.697-1.099) | 0.250 | 1.150 (0.906-1.459) | 0.250 | 0.949 (0.705-1.277) | 0.729 | |||
| Subacute pain | Model 1 | 1.098 (0.775-1.557) | 0.598 | 1.009 (0.710-1.433) | 0.961 | 1.006 (0.679-1.491) | 0.975 | ||
| Model 2 | 1.184 (0.824-1.702) | 0.361 | 1.121 (0.763-1.645) | 0.561 | 1.072 (0.664-1.730) | 0.776 | |||
| Model 3 | 1.177 (0.818-1.692) | 0.380 | 1.062 (0.722-1.562) | 0.760 | 0.936 (0.567-1.544) | 0.795 | |||
| Chronic pain | Model 1 | 1.365 (1.149-1.622) | < 0.001 | 1.291 (1.082-1.541) | 0.005 | 1.874 (1.579-2.224) | < 0.001 | ||
| Model 2 | 1.359 (1.137-1.624) | 0.001 | 1.260 (1.039-1.528) | 0.019 | 1.735 (1.413-2.132) | < 0.001 | |||
| Model 3 | 1.324 (1.106-1.585) | 0.002 | 1.186 (0.977-1.439) | 0.085 | 1.492 (1.208-1.842) | < 0.001 | |||
2.3. 影响WWI与慢性疼痛关系的主要协变量
模型1、2、3的结果均显示随着WWI升高，慢性疼痛风险增加，表 3所示为模型3中人口学数据、吸烟饮酒情况、体力活动和糖尿病患病情况等协变量对慢性疼痛的影响，当以WWI四分位数分组为主要变量时，慢性疼痛参与者更可能是女性，年龄40~59岁，目前吸烟或曾经吸烟，患有糖尿病，非西班牙裔白人；而与慢性疼痛风险降低相关的可能因素有未婚状态，较高的收入水平，日常饮酒2杯以内或2杯以上，轻度体力活动。
表 3.
体重校正腰围指数与慢性疼痛的无序多分类Logistic回归分析
Multinomial Logistic analysis on the associations between weight-adjusted waist index and chronic pain
| Variable | Weight-adjusted waist index as the main variable | |
| OR(95%CI ) | P | |
| PIR, poverty income ratio. | ||
| Gender/(male as reference) | ||
| Female | 1.430 (1.251-1.636) | < 0.001 |
| Age/(< 40 years as reference) | ||
| 40-59 | 1.468 (1.238-1.742) | < 0.001 |
| ≥60 | 0.920 (0.750-1.128) | 0.421 |
| Race/(non-hispanic whites as reference) | ||
| Non-hispanic blacks | 0.768 (0.658-0.897) | 0.001 |
| Mexican Americans | 0.412 (0.337-0.503) | < 0.001 |
| Other racial backgrounds | 0.709 (0.553-0.908) | 0.007 |
| Education level/(less than high school as reference) | ||
| High school | 0.916 (0.766-1.095) | 0.335 |
| Above high school | 0.858 (0.720-1.022) | 0.088 |
| Marital status/(married or living with a partner as reference) | ||
| Widowed or divorced or separated | 0.960 (0.818-1.126) | 0.616 |
| Never married | 0.583 (0.473-0.718) | < 0.001 |
| PIR/(< 1.0 as reference) | ||
| 1.0-2.9 | 0.774 (0.645-0.929) | 0.006 |
| ≥ 3.0 | 0.607 (0.496-0.744) | < 0.001 |
| Daily physical activity/(sedentary as reference) | ||
| Mild physical activity | 0.805 (0.695 -.932) | 0.004 |
| Moderate physical activity | 0.833 (0.683-1.015) | 0.069 |
| Severe physical activity | 0.954 (0.723-1.258) | 0.738 |
| Smoking/(never smokers as reference) | ||
| Former smokers | 1.887 (1.602-2.222) | < 0.001 |
| Current smokers | 1.364 (1.158-1.607) | < 0.001 |
| Alcoholic drinks per day/(no drinking as reference) | ||
| 1-2 glasses | 0.744 (0.628-0.881) | 0.001 |
| > 2 glasses | 0.708 (0.577-0.870) | 0.001 |
| Diabetes/(no diabetes as reference) | ||
| Yes | 1.591 (1.299-1.948) | < 0.001 |
| Borderline | 1.056 (0.647-1.724) | 0.827 |
| WWI/(Q1 group as reference) | ||
| Q2 | 1.324 (1.106-1.585) | 0.002 |
| Q3 | 1.186 (0.977-1.439) | 0.085 |
| Q4 | 1.492 (1.208-1.842) | < 0.001 |
3. 讨论
本研究利用具有代表性的NHANES数据库，阐明美国成人WWI水平与急性、亚急性和慢性疼痛之间的关系，研究结果显示，随着WWI升高，慢性疼痛的风险增加，而未见WWI与急性和亚急性疼痛的相关性。
疼痛是肥胖患者常见的共患病之一。随着BMI升高，疼痛的可能性增加，且肥胖与更严重的疼痛强度有关[14]。疼痛患者又因为久坐和因害怕或不能运动而暴饮暴食，导致更严重的肥胖[15]。肥胖与疼痛的共患病状态涉及多种机制: (1)肥胖患者的促炎状态可能加重疼痛，脂肪组织可释放大量促炎细胞因子(白细胞介素-6、肿瘤坏死因子、前列腺素等)[16]，这些细胞因子使得伤害感受器致敏，导致中枢神经系统的伤害感受输入增加[15, 17]；(2)肥胖导致整个骨骼系统和关节组织的机械应力增加，而关节组织的过度应力也可能导致关节软骨破裂，引起局部炎症和疼痛[18]；(3)肥胖也产生一些心理影响，如抑郁、自尊心受挫等也可加剧疼痛[19]；(4)与肥胖相关的饮食模式可能通过增加炎症和募集触发免疫反应的M1巨噬细胞来增强伤害性刺激[20]。因此，改善肥胖的各种方法都有利于改善疼痛结果，例如，体育锻炼、减肥手术等均具有积极作用[21-22]。
在评估肥胖与疼痛之间的关系时，通常应用BMI来评估肥胖程度。然而，BMI无法区分脂肪和肌肉质量，也无法区分腹部和外周脂肪[23]，而腹部内脏脂肪在代谢上与其他身体部位的脂肪不同，是疼痛的独立风险因素，而且腹部的脂肪组织释放多种全身炎症标志物，这些标志物可能与疼痛的病理生理学有关[24-26]，因此，需要能反映腹部脂肪含量的肥胖指标以更精确地评价肥胖和疼痛之间的关系。WWI与腹部脂肪量呈正相关，与肌肉量和骨量呈负相关[27]。我们的研究结果表明，更能代表腹部肥胖的WWI与慢性疼痛的发生呈正相关。一项横断面研究也有类似发现，代谢综合征在生理上与慢性疼痛有关，腹部肥胖是慢性疼痛的最强预测因素[28]。还有研究表明，WWI与抑郁症、糖尿病和认知功能障碍呈正相关[29-31]，这是影响体质量和疼痛关系的重要因素[32]。
本研究发现，WWI与慢性疼痛的相关性受多种混杂因素影响，如性别、年龄、收入水平、合并糖尿病等，这些也是目前常见的影响慢性疼痛的生理、心理和社会因素[33-34]，对这些因素的关注和调整可能改善慢性疼痛的患病率和严重程度。
本研究的局限性有：(1)NHANES数据库中的疼痛数据是通过问卷调查自我报告的，可能会受到回忆偏差的影响；(2)研究数据来自美国居民，种族间疼痛相关因素差异较大，而且没有合并症和用药相关数据；(3)因为横断面研究的限制，本研究不能证实WWI与慢性疼痛的因果关系。
综上所述，本研究发现，随着WWI升高，慢性疼痛的风险增加，但未见WWI与急性和亚急性疼痛的相关性，提示控制腹型肥胖可能有助于慢性疼痛的防治。
Footnotes
利益冲突 所有作者均声明不存在利益冲突。
作者贡献声明 刘慧丽：分析数据，撰写论文；闻蓓：分析数据；白雪、陈明安：收集数据；李民：提出研究思路，总体把关和审定论文。
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