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Table 4 Logistic regression model for the probability of at least one mental health service for those over the age of 65

From: A prospective study of mental health care for comorbid depressed mood in older adults with painful osteoarthritis

Model 1: Regression Model with SF-36 Mental Health Score as the Only Independent Variable (R-square = 0.080)

Independent variable

Odds Ratio

95% confidence interval

p-value

SF-36 Mental Health score per 10-point deterioration

1.3

1.23 to 1.38

< 0.0001

Model 2: Regression Model for the Effect of SF-36 Mental Health Score, Adjusted for Additional Covariates* (R-square = 0.124)

Independent variable

Odds ratio

95% confidence interval

p-value

Age per 10-year increase in age

0.8

0.68 to 0.95

0.012

Female sex (baseline is male)

1.79

1.37 to 2.34

< 0.0001

Urban region (reference is rural)

1.36

1.08 to 1.71

0.0083

Interaction between mental and general health†

  

0.0009

   Effect of a 10-point deterioration in general health score

1.04

0.97 to 1.11

0.32

   when mental health score = 56 (25th percentile for mental health score; poor mental health)

   

   Effect of a 10-point deterioration in general health score when mental

1.11

1.05 to 1.18

0.0007

   health score = 72 (median mental health score)

   

   Effect of a 10-point deterioration in general health score when mental

1.15

1.10 to 1.21

< 0.0001

   health score = 84 (75th percentile mental health score; good mental health)

   

   Effect of a 10-point deterioration in mental health score when general

1.2

1.12 to 1.29

< 0.0001

   health score = 35 (25th percentile general health score; poor health)

   

   Effect of a 10-point deterioration in mental health score when general

1.28

1.20 to 1.37

< 0.0001

   health score = 50 (median general health score)

   

   Effect of a 10-point deterioration in mental health score when general health score = 67 (75th percentile general health score; good health)

1.38

1.26 to 1.52

< 0.0001

  1. * Additional covariates that were considered in the regression analysis were: age, sex, number of comorbid conditions, SF-36 general health score, WOMAC total score and pain subscale, education, income, living arrangements, marital status, region, and race. An interaction between age and sex was also included. Interactions between the mental health score and the other variables were included in order to allowed the effect of mental health to vary by sub-group. All significant covariates are reported.
  2. † The significant interaction between the SF-36 mental health score and the SF-36 general health score means that both scores are significant predictors of the number of mental health visits, and that the effect of the mental health score varies with general health and the effect of the general health score varies with mental health. To illustrate the form of the interaction, the effect of increasing mental health score is presented for each of 3 representative ages (the 25th percentile age, the median age, and the 75th percentile age); and the effect of increasing age is presented for each of 3 representative mental health scores (the 25th percentile score, the median score, and the 75th percentile score). For younger patients, the odds of a mental health visit decreases as the score improves; whereas for older patients, the odds of a mental health visit are not affected by the score. For patients with the worst (lowest) mental health scores, the odds of a mental health visit decrease with increasing age, whereas for patients with better (higher) mental health scores, the odds are less affected by age.