Table 1—

Overall comparison of medication adherence by demographic factors

Demographic characteristicsMetformin
Placebo
nPercent adherentnPercent adherent
Age (years)
    25–4429365.930270.1
    45–5951972.553077.3
    ≥6020870.619281.0
    P value0.010.0001
Sex
    Male34873.731678.4
    Female67268.470874.9
    P value0.010.07
Ethnicity/race
    Caucasian57773.455080.7
    African American20966.421167.0
    Hispanic15065.015873.0
    American Indian5267.55972.1
    Asian3268.54675.3
    P value0.008<0.0001
Income*
    <$20,00012660.114676.8
    $20,000 to <$35,00016566.118175.6
    $35,000 to <$50,00020374.720674.6
    $50,000 to <$75,00021270.020178.6
    ≥$75,00023177.221078.6
    Refused8264.78065.1
    P value<0.00010.01
Marital status
    Never married12667.412777.8
    Living together2962.44475.7
    Married63272.563675.5
    Separated3164.62768.9
    Divorced15267.314577.2
    Widowed5065.84577.3
    P value0.090.72
Education (years)
    ≤1225868.827076.2
    13–1648469.649775.1
    ≥1727872.625777.2
    P value0.330.66
  • *

    * The adherence difference between metformin and placebo is consistent across age, sex, ethnicity, marital status, and education. However, heterogeneity is observed for income levels (P = 0.01). Those with <$20,000 income had the biggest gap in adherence between metformin and placebo.