After a study period of 1 year, we contacted patients and asked them to complete exit interviews. A total of 417 (82%) returned follow-up questionnaires. Self-reported health status measures provided patient outcome data on changes in health status during the study period.
Medical care was provided by 26 family practice and 79 general internal medicine second- and third-year residents. Those 105 primary care physicians each saw an average of 4.8 patients (standard deviation = 4.6 patients).
Resource Use and Medical Charges
Medical center resource use for the 1 year of care was determined by review of the comprehensive unified medical record. Physician reviewers noted the number of primary care visits, specialty clinic visits, emergency department visits, hospitalizations, and laboratory, diagnostic, and radiological tests (diagnostic services). Medical charges for all these services were obtained from the institutional central billing unit used by both clinics. Charges, used as a proxy for medical costs, were assigned to 1 of 5 categories: primary care clinics, specialty care clinics, emergency departments, hospitals (including outpatient surgical), and diagnostic services. In addition, yearlong totals for the 5 types of charges were calculated for each patient.
Results
As shown in Table 1, the 509 study patients included 315 women (62%) and 194 men (38%). Mean age and ethnicity were not significantly different for the 2 genders. Women, however, had significantly lower mean education, income, and self-reported physical and mental health status as measured by the respective SF-36 components.
The use of health care services by men and women was compared with 2-tailed Student t tests Table 2. Women had a significantly higher mean number of visits to their primary care clinic (P = .0004) and a significantly higher mean number of diagnostic services ordered (P = .0005). There were no statistically significant gender differences in the mean number of specialty clinic visits, emergency department visits, or hospitalizations.
The mean and median annual per capita expenditures for the 5 categories of medical charges (and total charges) for women and men are displayed in Table 3. To reduce the influence of outliers, the natural logarithm of these charges (plus $10) was used to examine gender differences in medical care charges using 2-tailed Student t tests to compare the 5 categories of medical charges Table 4. Women had significantly higher primary care (P = .0010), specialty clinic (P = .0487), emergency department (P = .0065), diagnostic services (P = .0016), and total charges (P = .0037) than men. There was no significant difference in hospital charges.
Regression equations were then estimated to relate the logarithm of medical charges of all categories to gender, controlling for clinic assignment, self-reported physical and mental patient health status, age, education, and income Table 5. Clinic assignment was significantly related to primary care and emergency department charges. Approximately 17% of the variation in log-transformed total charges was explained by clinic assignment, physical and mental health status, age, education, income, and patient gender. Because the dependent variable is expressed in logs, exponentiation of the estimated coefficients for any of the indicator variables (for example, the coefficient 0.1468 for the variable “female” in the primary care equation) provides the percentage by which average charges for those patients having that characteristic exceed average charges for those who do not. Thus, women had 15.8% higher charges for primary care clinic visits than men. They also had 9.4% greater charges in specialty clinics, 9.6% higher charges for emergency department care, and 10.4% greater charges for diagnostic services. Overall, their charges exceeded those of men by a statistically and clinically significant 9.9%. Predictably, physical health status and age were significantly related to medical charges.
Following a year of care, we calculated change in self-reported health status (exit health status minus entry health status). There were no significant differences in change of physical or mental health status (P = .0651 and .3691, respectively) for women compared with men. The trend for women to report their physical health status as improved to a greater extent than men should be noted.
Discussion
Previous studies reporting that women use more medical services than men have suggested that this is due to gender differences in morbidity and self-reported health status.1-4,6 Indeed, women in our study reported both baseline physical and mental health status significantly lower than the men. We found the subsequent mean numbers of primary care visits and diagnostic services were significantly higher for women than for men. Primary care physicians may be more likely to order laboratory, radiologic, and other diagnostic tests for women who make more frequent visits and have continuing medical complaints. We did not, however, observe the higher referral rates to specialty care for men that others have found.7