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Socioeconomic conditions and number of pain sites in women

BMC Women's Health201212:7

DOI: 10.1186/1472-6874-12-7

Received: 27 September 2011

Accepted: 29 March 2012

Published: 29 March 2012

Abstract

Background

Women in deprived socioeconomic situations run a high pain risk. Although number of pain sites (NPS) is considered highly relevant in pain assessment, little is known regarding the relationship between socioeconomic conditions and NPS.

Methods

The study population comprised 653 women; 160 recurrence-free long-term gynecological cancer survivors, and 493 women selected at random from the general population. Demographic characteristics and co-morbidity over the past 12 months were assessed. Socioeconomic conditions were measured by Socioeconomic Condition Index (SCI), comprising education, employment status, income, ability to pay bills, self-perceived health, and satisfaction with number of close friends. Main outcome measure NPS was recorded using a body outline diagram indicating where the respondents had experienced pain during the past week. Chi-square test and forward stepwise logistic regression were applied.

Results and Conclusion

There were only minor differences in SCI scores between women with 0, 1-2 or 3 NPS. Four or more NPS was associated with younger age, higher BMI and low SCI. After adjustment for age, BMI and co-morbidity, we found a strong association between low SCI scores and four or more NPS, indicating that there is a threshold in the NPS count for when socioeconomic determinants are associated to NPS in women.

Keywords

Socioeconomic conditions Number of pain sites/locations Women Co-morbidity Cancer survivors

Background

Living in deprived socioeconomic conditions is associated with higher prevalence of health complaints [1, 2], like generalized [3], musculoskeletal [4], chronic non-malignant [5] and complex/frequent/intensive pain [6]. The most frequent measures of self-reported pain are frequency, severity, and specific pain locations. During the recent years number of pain sites (NPS) is regarded as a better parameter in pain assessment [7] and may be more important than actual sites in determining the impact on health [8] and functioning [9]. Females endorse a larger NPS than males [7, 1012], and high NPS is frequently reported around middle age [7, 12, 13]. Increasing NPS is related to impaired health status [10, 12], and poorer general [9, 14], as well as physical, psychological and social functioning outcomes [15]. However, little is known regarding the association between socioeconomic conditions and NPS. The aim of this study was to explore the relationship between socioeconomic conditions and NPS in women.

Materials and methods

Study population

The study population comprised recurrence-free long-term gynecological cancer survivors and women from the general population. From 1987 through 1996, 1171 primary patients of cervical, corpus and ovarian cancer were treated at St. Olav's Hospital, Trondheim, which represent all gynecological cancer patients from the middle part of Norway. In May 2003 we examined survival and recurrence status. Women aged 30-75 years and without recurrence of disease, were eligible for participation in this cross-sectional study - in total 369 cases. For each survivor we selected four age-matched women as controls, living in the same county, at random from the population census. We failed to reach 50 cases due to invalid mailing addresses. Thus, the final sample comprised 319 gynecological cancer survivors and 1276 women from the general population. After one reminder, 176 survivors (55%) and 521 controls (41%) responded. Some had incomplete responses to most questions and were excluded. In total, 653 responses were included in the analyses; 160 women with and 493 without a history of gynecological cancer. Mean age was 58 and 57, respectively. The mean follow-up time after cancer treatment was 12 years (SD 2.6; range 8-17). More detailed information on the study population is provided elsewhere [1618].

Socioeconomic condition

The Socioeconomic Condition Index (SCI) [17] is a modification of the Living Condition Index [19], based on the scores on education, employment, income, ability to pay bills, self- perceived health, and satisfaction with the number of close friends. Education: < 10 years = 0;

10-12 years = 2; 13-15 years = 3; > 15 years = 4. Employment status: unemployed = 0; part- time job = 2; full-time job = 4. The unemployed group included homemakers, students, retired, and women with a disability pension. Annual household income: < 12.500 € = 0;

12.500 - 37.500 € = 2; 37.501-62.500 € = 3; > 62.500 € = 4. Ability to pay bills: never problems = 2; problems = 0. Self-perceived health: very poor = 0; poor = 1; moderate = 2; good = 3; very good = 4. Satisfaction with number of close friends: satisfied with number of close friends = 2; not satisfied with number of close friends = 0.

The summary scores of the SCI range from 0 to 20 and were categorized into quartiles; poor (score ≤ 24 percentile), average to poor (score 25-49 percentile), average to good (score 50-74 percentile), and good (score ≥ 75 percentile) SCI.

Number of pain sites

A body outline diagram was divided into 30 different areas; 15 on each side of the body, enabling the respondents to locate pain that they had experienced during the past week. As most studies apply an upper limit of 7-10 NPS [812, 15, 20, 21], we localized pain to eight body regions: head; neck; chest/stomach; lower abdomen/pelvis/hips; back/buttock; thigh/knees; legs/feet; arms/hands. The marked regions of pain were summarized into NPS (range 0-8).

Variable specification

The questionnaire also contained questions on potential confounding variables, such as age, marital status (single, married/co-habitant), weight and height (calculation of body mass index, BMI; kg/m2), smoking (yes, previous, never), and co-morbidity. Co-morbidity was measured as diseases/conditions over the past 12 months prior study, with yes/no responses. All questions were assessed by the respondent herself.

Statistical analyses

All questionnaires were scanned. Consistency analyses were run and corrected for appropriate variables. All analyses were carried out with SPSS version 17.0, applying Chi-square test and forward stepwise logistic regression to examine determinants associated to NPS. Outcome measures were adjusted odds ratios (aOR) with 95% confidence interval (CI). We have used p ≤ 0.05 as level of statistical significance. All reported p-values are two-sided.

Ethics

The study was approved by the Regional Committee for Medical Research Ethics, Mid- Norway, the Norwegian Data Inspectorate, and The National Department of Health and Social Affairs, Norway. All respondents gave informed written consent.

Results

There were only minor differences in the prevalence of women reporting 0, 1, 2, 3, and 4 or more pain sites (20.2%, 21.1%, 20.2%, 15.8%, and 22.7%, respectively). Pain in the neck was most prevalent (49.9%) followed by pain in the back/buttock (45.2%), lower abdomen/pelvis/hips (35.4%), and thighs/knees (33.8%) (Table 1).
Table 1

Pain site responses and total number of pain sites (NPS)

Pain site

N = 653

%

Head

148

22.7

Neck

326

49.9

Chest/stomach

91

13.9

Low abdom/pelvis/hips

231

35.4

Back/buttock

295

45.2

Thigh/knees

221

33.8

Legs/feet

162

24.8

Arms/hands

166

25.4

No. of pain sites (NPS)

  

0

132

20.2

1

138

21.1

2

132

20.2

3

103

15.8

4

73

11.2

5

43

6.6

6

23

3.5

7

9

1.4

8

0

0

For the remaining analyses, we categorized NPS as 0, 1-2, 3, and 4-7 pain sites. As displayed in Table 2 age, smoking, and satisfaction with number of close friends were equally distributed among the NPS groups. More women reporting 3 NPS had high BMI. However, in all major factors the differences in the distribution within the NPS groups were found between women reporting 4-7 NPS and those reporting 3 or less NPS. Women with 4-7 NPS were more often single, had lower education, were more often unemployed, had lower income, more problems paying their bills, and poorer general health (Table 2). The SCI summarizes the differences in education, employment status, income, ability to pay bills, self-perceived health, and satisfaction with number of close friends. In total, women with the lowest SCI had the highest NPS (p < 0.001).
Table 2

Study population characteristics by number of pain sites (NPS)

  

Number of pain sites

  
 

N

0

1-2

3

4-7

%

P-value*

 

653

20.2

41.3

15.8

22.7

100

 

Age

      

P < 0.55

30-49

168

17.9

44.6

18.5

19.0

100

 

50-59

188

18.6

41.0

16.5

23.9

100

 

60-75

297

22.6

39.7

13.8

23.9

100

 

Marital status

      

P < 0.04

Single

152

21.7

32.9

15.1

30.3

100

 

Married/cohabit.

501

19.8

43.9

16.0

20.4

100

 

BMI (kg/m2)

      

P < 0.03

< 25

324

24.7

40.7

11.7

22.8

100

 

25-30

241

17.4

40.2

19.5

22.8

100

 

> 30

88

11.4

46.6

20.5

21.6

100

 

Smoking

      

P < 0.16

Yes

185

15.1

39.5

15.7

29.7

100

 

Previous

227

22.5

42.3

15.4

19.8

100

 

Never

241

22.0

41.9

16.2

19.9

100

 

Education

      

P < 0.10

< 10 yrs

200

16.5

41.0

15.5

27.0

100

 

10-12 yrs

186

18.3

38.2

16.1

27.4

100

 

13-15 yrs

140

24.3

41.4

15.7

18.6

100

 

> 15 yrs

127

24.4

46.5

15.7

13.4

100

 

Employment status

      

P < 0.01

Unemployed

326

17.8

35.9

14.7

31.6

100

 

Part-time

84

21.4

42.9

16.7

19.0

100

 

Full-time

243

23.0

48.1

16.9

11.9

100

 

Income (Euro)

      

P < 0.01

< 12.500

33

15.2

45.5

12.1

27.3

100

 

12.500-37.500

186

18.8

32.8

15.1

33.3

100

 

37.501-62.500

193

19.7

42.5

16.1

21.8

100

 

> 62.500

241

22.4

46.5

16.6

14.5

100

 

Problem paying bills

      

P < 0.01

Never

533

22.0

42.8

14.4

20.8

100

 

Sometimes/often

120

12.5

35.0

21.7

30.8

100

 

Satisfied no. friends

      

P < 0.70

Yes

536

20.1

42.4

15.5

22.0

100

 

No

117

20.5

36.8

17.1

25.6

100

 

General health

      

P < 0.001

Poor

119

7.6

18.5

21.0

52.9

100

 

Moderate

158

7.6

44.3

19.0

29.1

100

 

Good

176

18.2

48.9

19.9

13.1

100

 

Very good

200

39.5

46.0

6.5

8.0

100

 

SCI

      

P < 0.001

≤ 24

140

15.0

34.3

15.0

35.7

100

 

25-49

170

18.8

35.3

18.2

27.6

100

 

50-74

167

18.0

46.7

14.4

21.0

100

 

≥ 75

176

27.8

47.7

15.3

9.1

100

 

*Chi-square test

The SCI quartiles [poor (score ≤ 24 percentile), average to poor (score 25-49 percentile), average to good (score 50-74 percentile), good (score ≥ 75 percentile)] were evenly distributed by BMI and by co-morbidities such as pulmonary, gastrointestinal, kidney/urinary, skin disorders and migraine/headache. Poor/average to poor SCI-score was more frequent in high age, among singles and smokers, as well as among women who had survived gynecological cancer, had cardiovascular disease, hypertension, diabetes, and musculoskeletal, psychiatric and sleeping disorder (Table 3).
Table 3

Demographic factors and co-morbidity by Socioeconomic Condition Index (SCI)

  

SCI (quartiles)

 
 

N

≤ 24 Poor

25-49

50-74

≥ 75 Good

%

P-value*

 

653

21.4

26.0

25.6

27.0

100

 

Age

      

P < 0.001

   30-49

168

10.7

16.7

29.2

43.5

100

 

   50-59

188

8.5

24.5

24.5

42.6

100

 

   60-75

297

35.7

23.2

24.2

7.7

100

 

Marital status

      

P < 0.001

   Single

152

36.2

34.2

16.4

13.2

100

 

   Married/cohabit.

501

17.0

23.6

28.3

31.1

100

 

BMI (kg/m2)

      

P < 0.22

   < 25

324

20.1

22.8

28.4

28.7

100

 

   25-30

241

21.6

28.2

22.8

27.4

100

 

   > 30

88

26.1

31.8

22.7

19.3

100

 

Smoking

      

P < 0.001

   Yes

185

34.1

27.6

20.5

17.8

100

 

   Previous

227

16.7

23.3

28.6

31.3

100

 

   Never

241

16.2

27.4

26.6

29.9

100

 

History of gyn. cancer

      

P < 0.02

   Yes

160

26.9

31.3

22.5

19.4

100

 

   No

493

19.7

24.3

26.6

29.4

100

 

Cardiovascular dis.

      

P < 0.04

   Yes

28

39.3

25.0

28.6

7.1

100

 

   No

625

20.6

26.1

25.4

27.8

100

 

Hypertension

      

P < 0.001

   Yes

142

29.6

31.7

21.8

16.9

100

 

   No

511

19.2

24.5

26.6

29.7

100

 

Diabetes

      

P < 0.05

   Yes

25

36.0

40.0

8.0

16.0

100

 

   No

628

20.9

25.5

26.3

27.4

100

 

Migraine/headache

      

P < 0.40

   Yes

243

18.1

28.4

26.7

26.7

100

 

   No

410

23.4

24.6

24.9

27.1

100

 

Musculoskeletal dis.

      

P < 0.001

   Yes

148

25.0

37.8

23.0

14.2

100

 

   No

505

20.4

22.6

26.3

30.7

100

 

Psychiatric dis.

      

P < 0.001

   Yes

72

34.7

22.2

29.2

13.9

100

 

   No

581

19.8

26.5

25.1

28.6

100

 

Sleeping disorder

      

P < 0.001

   Yes

185

27.0

31.9

25.4

15.7

100

 

   No

468

19.2

23.7

25.6

31.4

100

 

*Chi square test

Variables such as SCI (Table 2) and co-factors (Table 3) that were predictors (p < 0.10) of NPS in univariate analyses entered forward stepwise logistic regression analyses. Three models were tested: model A (1-2/0 NPS), model B (3/0 NPS), and model C (4-7/0 NPS), with the no-pain-sites group as reference. In all models we adjusted for co-morbidity. Being a gynecological cancer survivor was not associated with NPS in any model. A significant association was found for increasing BMI and NPS in all three models, with no difference between obese and overweight women. Age below 60 years was associated to 3 or more NPS (models B and C) with no difference between the age-groups 30-49 and 50-59 years. A significant association by decreasing SCI and 4-7 NPS was found in model C, but not in model A or B. Although aOR in the lowest SCI quartiles was 4.2 (95% CI: 1.3-13.5) for the 3/0 NPS group (model B), the strongest association between SCI and NPS was found for the lowest quartile of SCI in model C (aOR 16.9; 95% CI: 4.6-61.7) (Table 4). There was no effect modification between any of the significant variables and co-morbidity in any model.
Table 4

Predictors of number of pain sites (NPS)

 

Model A*

Model B**

Model C***

NPS analyzed

1-2/0

3/0

4-7/0

N controls

132

132

132

N cases

270

103

148

Adjusted odds ratio (aOR)/

Variables

aOR (95% CI)

aOR (95% CI)

aOR (95% CI)

Age

   

30-49

1.4 (0.7-2.6)

5.5 (1.9-15.8)

2.9 (0.99-8.5)

50-59

1.5 (0.8-2.8)

4.3 (1.6-11.4)

4.5 (1.6-12.1)

60-75

1.0 (ref.)

1.0 (ref.)

1.0 (ref.)

BMI (kg/m2)

   

< 25

1.0 (ref.)

1.0 (ref.)

1.0 (ref.)

25-30

1.5 (0.92-2.4)

3.3 (1.6-6.8)

2.3 (1.0-5.2)

> 30

2.7 (1.2-5.9)

5.4 (1.8-16.5)

1.7 (0.5-5.8)

History of gyn. cancer

   

Yes

0.97 (0.6-1.7)

1.4 (0.7-3.1)

1.3 (0.6-3.1)

No

1.0 (ref.)

1.0 (ref.)

1.0 (ref.)

SCI

   

≤ 24

1.7 (0.8-3.7)

4.2 (1.3-13.5)

16.9 (4.6-61.7)

25-49

1.1 (0.6-2.3)

1.5 (0.5-4.0)

6.6 (2.0-21.7)

50-74

1.5 (0.8-2.8)

2.1 (0.9-5.2)

6.6 (2.1-20.5)

≥ 75

1.0 (ref.)

1.0 (ref.)

1.0 (ref.)

* Adjusted for musculoskeletal disorders and migraine/headache

**Adjusted for musculoskeletal disorders, migraine/headache, and sleeping disorders

*** Adjusted for musculoskeletal disorders, migraine/headache, sleeping and psychiatric disorders

Discussion

Major differences in the socioeconomic conditions, measured by SCI, were found between women reporting 4 or more NPS and those reporting 3 or less NPS. The socioeconomic conditions are fairly equal for women reporting 0, 1-2 or 3 NPS (Table 2), with employment status corresponding to women in the general Norwegian population [22]. More women with

4-7 NPS, on the other hand, live under the poorest socioeconomic conditions (Table 2). We did not find a clear socioeconomic gradient in NPS, but a threshold when socioeconomic determinants are associated to NPS. After adjustment for co-factors (Table 3) the strongest association between SCI and NPS was found for women with the lowest SCI scores (Table 4). The association in the other groups is rather modest.

The relationship between low socioeconomic conditions and high NPS could be explained by determinants of social position. Although this relationship has been found for some marginalized groups, there is limited scientific evidence for such associations [23]. On the contrary, components of social position, like material circumstances, lifestyle, and psychosocial factors, have been found to increasingly determine health outcomes. The psychosocial perspective proposes that impaired health is a consequence of long-term stress. Lack of control [24] and relative deprivation [25] may represent the key elements of this association, as both phenomena are related to the lower levels of the social hierarchy in modern societies. Adverse psychosocial environment and low job control [1] as well as experiences of being belittled, lack of social support, and economic hardship [26] is associated with poor self-rated health. Women in deprived socioeconomic positions may experience constant stress due to such unfavorable factors, affecting an imbalance in their hormonal and immune systems [27], leading to pain conditions. Within this context we explain the significant association between low socioeconomic conditions and NPS.

Although a relationship between living in socioeconomic deprived areas and widespread pain has been demonstrated earlier [4], the present study reveals that there is a strong relationship between low socioeconomic status and high NPS. In most studies examining NPS, NPS is treated as a co-factor, with chronic pain [8, 11] or disability [21] as outcome variables. In only one study was NPS treated as the dependent variable [12], indicating an association between three components of socioeconomic condition (education, marital and employment status) and NPS in both sexes. However, in that particular study adjustment for co-morbidity was not performed. After adjustment for co-morbidity, we found a strong association between poor

SCI (lowest quartile) and 4 or more NPS, indicating that there is a threshold for most determinants on NPS. In a wealthy country as Norway, women with an average socioeconomic position (≥ 25 and < 75 percentile of SCI) hardly report any higher NPS than women in the best socioeconomic position (≥ 75 percentile of SCI).

Unfortunately, disadvantaged and less assertive women may lack sufficient resources to perform as a credible patient within a normative, biomedical frame of reference. According to Werner and Malterud [28], Norwegian women with chronic pain exert themselves extensively in order to appear as what they hope is "just right" during medical encounters, i.e. substantial effort from the patient's side is required to get access to health care benefits. Health care professionals should be extra attentive to subtle and unarticulated ill-health symptoms of women living in the lowest socioeconomic position to try and reduce the persistent social inequalities in health outcomes [1, 2].

As reported in other Scandinavian studies [7, 12, 13], we found the highest NPS among women below 60 years of age (Table 4). In accordance with Kamaleri et al. [12], we found a weak association between NPS and overweight, whereas smoking and being a gynecological cancer survivor was not associated with NPS in any model. Traumas as war [20] or frightening accidents [29] have been associated with NPS later in life, but surviving cancer without recurrence seems to be very different from surviving other traumas.

The sample size (N = 653) and the high completeness of reported data, including pain areas on the body chart, are considered strengths of the present study. The prevalence of women reporting no, one, two, three, or 4-7 pain sites (Table 1) is similar to what is reported in another Norwegian study [12], supporting the external validity of the study. We consider the use of SCI as strength of the study, and we avoid the problems of co-linearity in multivariate models applying a single outcome for socioeconomic conditions. One limitation of the present study is the cross-sectional design. We cannot draw strict conclusions on causality as the relationship between socioeconomic conditions and NPS is very complex and interactive. Another limitation is the relatively modest response rate. However, the response-rate among gynecological cancer survivors and their controls selected at random from the general population, 55% and 41%, respectively, is considered high, related to comparable studies [4, 13, 30]. There was no skewed distribution between respondents and non-respondents among survivors and women selected at random from the general population regarding age (quartiles) or marital status (married/single) (data not shown).

Conclusion

After adjustment for age, BMI and co-morbidity, we found a strong association between low SCI score and four or more NPS, indicating that there is a threshold in the NPS count for when socioeconomic determinants are associated to NPS in women.

Funding

The study was funded by a grant from SINTEF Health, Trondheim, Norway, and by a grant from the Sør-Trøndelag University College, Faculty of Nursing, Trondheim, Norway.

Abbreviations

BMI: 

Body mass index

SCI: 

Socioeconomic condition index

NPS: 

Number of pain sites

Declarations

Authors’ Affiliations

(1)
Research Centre for Health Promotion and Resources HiST/NTNU, Sør-Trøndelag, University College, Faculty of Nursing
(2)
Department of Infectious Disease Epidemiology, Norwegian Institute of Public Health
(3)
Women's Health and Perinatology Research Group, Department of Clinical Medicine, Faculty of Health Sciences, University of Tromso

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  31. Pre-publication history

    1. The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1472-6874/12/7/prepub

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© Rannestad and Skjeldestad; licensee BioMed Central Ltd. 2012

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