At the same patient at the same time can occur independently from each other or be combined different diseases. In such cases, both the doctor and the patient seek to understand whether one disease triggered the development of another, whether these diseases are somehow related, or whether they originated independently of each other.

For example, patients with diabetes often develop retinal, heart, and kidney damage. All these disorders are complications of the primary disease – diabetes. In contrast, patients with schizophrenia have an increased risk of mood disorders such as comorbid disease. Finally, a patient with an elevated level of cholesterol in the blood may develop bursitis as a separate independent disease.

To measure comorbidity, the odds ratio indicator (OR) is often used. This statistical term is used when comparing the probabilities of comorbid diseases in two different groups. Probability is calculated by comparing the number of patients suffering from a particular pathology with a number of patients who do not have this disease in a certain time period.

With equal chances of developing the disease in the two compared groups, the OR is equal to one. This is observed if two diseases occur in combination with equal chances. If the OR is greater than one, this means that the joint development of both diseases is observed more often than separately. OSH less than one means that the development of diseases combined with each other occurs less frequently than separately.

The OR score is significant when evaluating the confidence interval (CI) of 95%. The confidence interval shows the range of possible values that are compared with the data obtained. The limiting values of the confidence interval are called the limits of the confidence interval. The confidence estimate is considered significant if the 95% CI does not include the number 1.0.

Another indicator characterizing comorbidity is the relative risk (RR), or the ratio of the patients of the study group to the number of patients of the control group. A RR equal to one indicates that there is no relationship, and a zero value of RR indicates a complete positive relationship.

The OR value can be similarly determined using a CI of 95%. In addition, a risk ratio (RIA) based on survival tests can be used to determine the OR. With ODS equal to one, the likelihood of disease is the same. With ODS equal to two, the incidence of the first group is two times higher than that in the other group. With ODS equal to 0.5, the disease occurs in half of the subjects.

A study conducted by the family medicine service revealed a wide range of adult diseases, both with and without a headache.