PREDICTING PHYSICAL AND MENTAL HEALTH OUTCOMES FROM PATIENTS' NUMERICAL SKILLS

Purpose: There is compelling evidence showing that health literacy influences health outcomes. However, there is a dearth of research investigating this issue in the vast literature on numeracy-the ability to accurately interpret and make good decisions based on numerical information about risk, a skill that is only moderately correlated with health literacy. We extend this literature by investigating whether numeracy predicts prevalence of comorbidity and number of prescribed medications. We also investigated whether numeracy predicts self-perceptions of physical and mental health.

Method: 502 individuals receiving outpatient care at a Veterans Affairs Medical Center reported their demographics and answered a survey measuring objective and subjective numeracy, trust in physicians, satisfaction with role in medical decision making, perceptions of physical and mental health, and unhealthy habits. We computed patients’ BMI and their age-adjusted Charlson index, an extensively studied comorbidity index for predicting mortality. We retrieved number of prescribed medications from medical records.

Result: Compared to patients with high objective numeracy, patients with low objective numeracy showed higher prevalence of comorbidity and took more medications. Patients with low subjectivenumeracy had more negative perceptions of their physical and mental health than those with high subjective numeracy. These conclusions hold after controlling for the effect of demographics, risky habits, BMI, trust in physicians, and satisfaction with role in decision making, suggesting that numeracy has a unique significant contribution to health outcomes beyond the effect of these factors.

Conclusion: Our research documents for the first time that self-reported numeracy is a reliable predictor of perceptions of health, whereas objective numeracy accurately predicts actual health. Our research lays the groundwork for future research on improving health outcomes by improving numeracy.