Random forest analysis of predictors of pain tolerance and beliefs
Description
The primary content of this repository includes the data, codebook, and analysis scripts (with associated markdown outputs and plots) for random forest analyses of predictors of cold-pain tolerance (cold-pain-tolerance.Rmd, cold-pain-tolerance.md), pressure-pain tolerance (pressure-pain-tolerance.Rmd, pressure-pain-tolerance.md), and acceptance of pain behaviours in males (apbq-male.Rmd, apbq-male.md) in healthy black (self-declared African ancestry) and white (self-declared European ancestry) young adults of both sexes in South Africa. Only complete cases were used in the random forest analysis (pain tolerances: 156/212 participants; ABPQ-M: 167/212 participants).
The repository also includes the data and codebook used in all bivariate analyses. These analyses were completed using GraphPad Prism 6.0, and the results have not been uploaded to the repository (please contact antonia.wadley@wits.ac.za or peter.kamerman@wits.ac.za for more information).
Bibliographic information
Bagwath Persad LA, Kamerman PR, Wadley AL. Predictors of cold and pressure pain tolerance in healthy South African adults. Pain Med [Epub - ahead of print], 2017. DOI: 10.1093/pm/pnw291.
License
MIT License
Copyright: Peter Kamerman (2016)
Repository contents
Overview of the study
###Background Studies on relationships between sex, ethnicity and pain largely have emanated from the US and Europe. We compared cold (CPT) and pressure pain tolerance (PPT) in male and female South Africans of African and European ancestry and assessed whether psychosocial factors (including pain beliefs) predicted differences in pain tolerance.
Methods
We recruited 106 (62 female) students of African ancestry and 106 (55 female) of European ancestry and subjected them to a cold-pressor test and pressure algometry. Socioeconomic status (SES), pain catastrophizing, depression, anxiety and pain beliefs were assessed as predictors of pain tolerance.
Results
CPT was lower in students of African compared to European ancestry (for both sexes), and PPT was lower in female than male students (for both ethnicities). Females were very accepting of men expressing pain and males less so. Males of African ancestry were least accepting but still tolerant. Multivariate analysis identified African ancestry, and particularly being a female of African ancestry as strong predictors of lower CPT. Anxiety was a weak predict of CPT. Sex was the only strong predictor of PPT on multivariate analysis (PPT females < males) and catastrophizing was a weak predictor . Female sex and African ancestry were strong predictors of acceptance of expression of pain in males. SES was a weak predictor of APBQ-M.
Conclusions
Despite a different cultural and social background from US and European cohorts, we saw similar patterns of sex and ethnic differences in CPT and PPT in an African cohort. Traditional psychosocial predictors of pain sensitivity predicted variation in the outcome variables but were not strong predictors.
Codebook
Random forest analysis
Data file: random-forest.csv
Codebook file: codebook-random-forest.csv
| Key | Notes |
| :———— | :————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————————— |
| ID | Participant identification code |
| CPT | Cold-pain tolerance: Time (in seconds) participants could retain their dominant hand in iced water (5oC). For safety, a maximum duration of 300s hand immersion was used. |
| PPT | Pressure-pain tolerance: Pressure (in kPa) applied to the nail bed of the index finger using a pressure algometer with a 10mm^2 probe (Algometer, Somedic AB, Sweden). For safety, a maximum pressure of 1500kPa was used. |
| ancestry | Self-identified ancestry (Afr: African ancestry, Eur: European ancestry) |
| sex | Self-identified biological sex (F: Female, M: Male) |
| anxiety | Anxiety was assessed using 10-item anxiety subscale of the Hopkins Symptom Checklist-25 (HSCL-25). Participants rated the extent to which they had experienced symptoms within the last week on a 4-point Likert scale. A mean subscale scores > 1.75 indicates clinically relevant levels of anxiety. |
| depression | Depression was measured using the 15-item depression subscale of the Hopkins Symptom Checklist-25 (HSCL-25). See Anxiety for details. |
| PCS | Pain Catastrophizing Scale was used to assess catastrophic thinking related to pain. The PCS was administered before exposure to the experimental pain stimuli to determine trait catastrophizing: Assesses the general tendency to catastrophize. Participants rated each of the 13 items on the questionnaire on a 5-point Likert scale. PCS scores > 30 indicate a clinically significant level of catastrophizing. |
| APBQ-F | Appropriate Pain Behavior Questionnaire - Female (APBQ-F): Assesses pain beliefs regarding females. A 14-item questionnaire that measures beliefs about the appropriateness of expressing pain in the presence of others. Eight items on the ABPQ express a positive attitude to pain expression, and 6 express a negative attitude towards expressing pain. Participants rated the extent to which they agreed with each of the 14 statements by scoring them on a 7-point Likert scale. APBQ was scored by calculating the difference between the mean score of the eight positive statements and six negative statements. The final score has a bounded range -6 to +6, with negative values indicating a bias against females expressing pain behaviours. |
| APBQ-M | Appropriate Pain Behavior Questionnaire - Male (APBQ-M): Assesses pain beliefs regarding males. See ABPQ-F for details. |
| education | Highest level of education completed by a parent or guardian [0: none, 1: primary school (grades 1 - 7), 2:,secondary school (grades 8 - 12), 3: tertiary education (post-secondary school)]. |
| assets | Average number of household assets owned by parents or guardians (five assets were assessed: refrigerator, television, car, microwave oven, and washing machine; 0: not owned, 1: owned). |
Bivariate analyses
Data file: bivariate-data.csv
Codebook file: codebook-bivariate-data.csv
| Key | Notes |
|---|---|
| id | Participant identification code. |
| ancestry | Self-identified ancestry (Afr: African ancestry, Eur: European ancestry) |
| sex | Self-identified biological sex (F: Female, M: Male) |
| age | Age in years |
| height | Height in metres (m) |
| mass | Body mass in kilograms (kg) |
| bmi | Body Mass Index in kg/m^2 |
| english_first_language | English as a first language (yes, no) |
| first_language_other | If first language was not English, what was it? |
| education | Years of formal education (years) |
| ses_parents_education | Highest education level achieved by parent(s)/guardian(s) (0: none, 1: primary school - grades 1-7, 2: secondary school - grades 8-12, 3: tertiary education) |
| ses_parents_employment | Parent(s)/guardian(s) current employment status (0: unemployed, 1: pensioner, 2: employed) |
| ses_housing_type | Type of primary residence (0: none, 1: shack, 2: hostel, 3: room/garage, 4: flat/cottage, 5: home shared with other families, 6: home not shared with other families) |
| ses_toilet | Type of toilet facilities at primary residence (0: none, 1: pit/bucket, 2: flush toilet - outside, 3: flush toilet - inside) |
| ses_bedrooms | Number of bedrooms at primary residence (0: 0, 1: 1, 2: 2, 3: 3, 4: 4 or more) |
| ses_refrigerator | Do you have a refrigirator at your primary residence (0: no, 1: yes) |
| ses_television | Do you have a television at your primary residence (0: no, 1: yes) |
| ses_car | Do you/your parents/guardians own a car (0: no, 1: yes) |
| ses_washing_machine | Do you have a washing machine at your primary residence (0: no, 1: yes) |
| se_microwave_oven | Do you have a microwave oven at your primary residence (0: no, 1: yes) |
| cpt_time | Cold-pain tolerance: Time (in seconds) participants could retain their dominant hand in iced water (5oC). For safety, a maximum duration of 300s hand immersion was used |
| cpt_vas | Rating of the intensity of pain when cold-pain tolerance was reached. Rating recorded on a 0-100mm visual analogue pain scale (VAS, anchored at: 0: no pain, and 100: worst pain imaginable) |
| ppt_kpa | Pressure-pain tolerance: Pressure (in kPa) applied to the nail bed of the index finger using a pressure algometer with a 10mm^2 probe (Algometer, Somedic AB, Sweden). For safety, a maximum pressure of 1500kPa was used |
| ppt_vas | Rating of the intensity of pain when pressure-pain tolerance was reached. Rating recorded on a 0-100mm visual analogue pain scale (VAS, anchored at: 0: no pain, and 100: worst pain imaginable) |
| hopkins_1_anx_scared | Suddenly scared for no reason (1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| hopkins_2_anx_fearful | Feeling fearful (1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| hopkins_3_anx_faintness | Faint, dizziness or weakness(1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| hopkins_4_anx_nervousness | Nervousness or shaking inside (1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| hopkins_5_anx_heart_pounding | Heart pounding or racing (1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| hopkins_6_anx_trembling | Trembling (1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| hopkins_7_anx_tense | Feeling tense or keyed-up (1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| hopkins_8_anx_headaches | Headaches (1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| hopkins_9_anx_terror | Spells of terror or panic (1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| hopkins_10_anx_restlessness | Feeling restless, cannot sit still (1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| hopkins_11_dep_low_energy | Feeling low in energy, slowed down (1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| hopkins_12_dep_self_blame | Blaming yourself for things (1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| hopkins_13_dep_cry | Crying easily (1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| hopkins_14_dep_libido | Loss of sexual interest or pleasure (1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| hopkins_15_dep_appetite | Poor appetite (1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| hopkins_16_dep_sleep | Difficulty falling asleep, staying asleep (1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| hopkins_17_dep_hopelessness | Feeling hopeless about the future (1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| hopkins_18_dep_sad | Feeling blue (1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| hopkins_19_dep_lonely | Feeling lonely (1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| hopkins_20_dep_suicidal | Thoughts of ending your life (1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| hopkins_21_dep_trapped | Feeling of being trapped or caught (1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| hopkins_22_dep_worrying | Worrying too much about things (1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| hopkins_23_dep_disinterest | Feeling no interest in things (1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| hopkins_24_dep_effort | Feeling everything is an effort (1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| hopkins_25_dep_worthlessness | Feeling worthlessness (1: not at all, 2: a little, 3: quite a bit, 4: extremely) |
| pcs_1 | I worry all the time about whether the pain will end (0: not at all, 1: to a slight degree, 2: to a moderate degree, 3: to a great degree, 4: all the time) |
| pcs_2 | I feel I cannot go on (0: not at all, 1: to a slight degree, 2: to a moderate degree, 3: to a great degree, 4: all the time) |
| pcs_3 | It is terrible and I think It is never going to get any better (0: not at all, 1: to a slight degree, 2: to a moderate degree, 3: to a great degree, 4: all the time) |
| pcs_4 | It is awful and I feel that it overwhelms me (0: not at all, 1: to a slight degree, 2: to a moderate degree, 3: to a great degree, 4: all the time) |
| pcs_5 | I feel I cannot stand it anymore (0: not at all, 1: to a slight degree, 2: to a moderate degree, 3: to a great degree, 4: all the time) |
| pcs_6 | I become afraid that the pain will get worse (0: not at all, 1: to a slight degree, 2: to a moderate degree, 3: to a great degree, 4: all the time) |
| pcs_7 | I keep thinking of other painful events (0: not at all, 1: to a slight degree, 2: to a moderate degree, 3: to a great degree, 4: all the time) |
| pcs_8 | I anxiously want the pain to go away (0: not at all, 1: to a slight degree, 2: to a moderate degree, 3: to a great degree, 4: all the time) |
| pcs_9 | I cannot seem to keep it out of my mind (0: not at all, 1: to a slight degree, 2: to a moderate degree, 3: to a great degree, 4: all the time) |
| pcs_10 | I keep thinking about how much it hurts (0: not at all, 1: to a slight degree, 2: to a moderate degree, 3: to a great degree, 4: all the time) |
| pcs_11 | I keep thinking about how badly I want the pain to stop (0: not at all, 1: to a slight degree, 2: to a moderate degree, 3: to a great degree, 4: all the time) |
| pcs_12 | There is nothing I can do to reduce the intensity of the pain (0: not at all, 1: to a slight degree, 2: to a moderate degree, 3: to a great degree, 4: all the time) |
| pcs_13 | I wonder whether something serious may happen (0: not at all, 1: to a slight degree, 2: to a moderate degree, 3: to a great degree, 4: all the time) |
| abpq_1_f_ok_to_cry | It is acceptable for women to cry when in pain (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_2_f_ok_to_tell_others | It is okay for women to communicate their pain to others (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_3_f_ok_to_frown | It is all right for women to frown when in pain (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_4_f_sympathy_towards | I feel sympathy towards women who are displaying pain (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_5_f_unacceptable_to_tell | It is unacceptable for women to tell others about their pain* (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_6_f_keep_private | I believe women should keep pain private* (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_7_f_ok_to_groan | It is all right for women to groan when in pain (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_8_f_ok_to_ignore | It is appropriate for women to ignore their pain* (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_9_f_weakness_to_show_pain | I regard it a sign of weakness for women to show pain* (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_10_f_ok_to_complain | It is okay for women to complain when in pain (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_11_f_acceptable_to_complain | It is acceptable for women to complain when in pain (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_12_f_appropriate_to_lie_down | It is appropriate for women to lie down when in pain (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_13_f_unacceptable_to_clutch_painful_area | It is unacceptable for women to bend over/clutch at the area in pain* (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_1_f_should_tolerate_pain | Women should be able to tolerate pain in most circumstances* (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_1_m_ok_to_cry | It is acceptable for men to cry when in pain (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_2_m_ok_to_tell_others | It is okay for men to communicate their pain to others (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_3_m_ok_to_frown | It is all right for men to frown when in pain (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_4_m_sympathy_towards | I feel sympathy towards men who are displaying pain (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_5_m_unacceptable_to_tell | It is unacceptable for men to tell others about their pain* (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_6_m_keep_private | I believe men should keep pain private* (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_7_m_ok_to_groan | It is all right for men to groan when in pain (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_8_m_ok_to_ignore | It is appropriate for men to ignore their pain* (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_9_m_weakness_to_show_pain | I regard it a sign of weakness for men to show pain* (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_10_m_ok_to_complain | It is okay for men to complain when in pain (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_11_m_acceptable_to_complain | It is acceptable for men to complain when in pain (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_12_m_appropriate_to_lie_down | It is appropriate for men to lie down when in pain (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_13_m_unacceptable_to_clutch_painful_area | It is unacceptable for men to bend over/clutch at the area in pain* (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
| abpq_1_f_should_tolerate_pain | men should be able to tolerate pain in most circumstances* (Likert-scale anchored at 1: stongly disagree, and 7: stongly agree) |
Note: The dataset does not contain any calculated scores. To calculate:
- Socio-economic assest score:
- Based on ownership of culturally relevant assets (refrigerator, televison, car, washing machine, microwave oven). Because the cohort consisted of full-time students we used parental/guardian ownership of material household items as proxies for participants’ asset ownership. The score was calculated by summing the number of assests ‘owned’, and dividing by the number of asset questions correctly completed.
- Pain Catastrophizing Scale score:
- Scores from each of the 13 statements were summed (the maximum score is 52 with a higher scores indicating a greater tendency to catastrophize. PCS scores > 30 indicate a clinically significant level of catastrophizing).
- Hopkins Symptom Checklist 25:
- Mean scores for the 10-item anxiety subscale and the 15-item depression subscale items were calculated (mean subscale scores > 1.75 indicate clinically relevant levels of anxiety or depression).
- Appropriate Pain Behaviours Questionnaire score:
- The Appropriate Pain Behavior Questionnaire (APBQ) was used to assess pain beliefs (Nayak et al., 2000). The questionnaire is a 14-item questionnaire that measures beliefs about the appropriateness of expressing pain in the presence of others. There are two components to the APBQ: the APBQ-Male (APBQ-M), which assesses how appropriate individuals find men expressing pain to be and the APBQ-Female (APBQ-F), which assesses how appropriate individuals find women expressing pain to be. Eight items on the ABPQ express a positive attitude to pain expression, and 6 express a negative attitude towards expressing pain. The APBQ score was calculated by taking the difference between the mean score of the eight statements that assess whether it is appropriate to express pain behaviors and the mean score of the six statements that assess whether it is inappropriate to express pain behaviors. The final score has a bounded range -6 to +6, with negative values indicating a bias towards pain expression being considered inappropriate and positive values indicating a bias towards pain expression being considered appropriate. We interpreted a score close to zero as indicating an individual had a neutral view of pain expression.