Table 4.
Ratio (MR) of the mean number of prescription fillings (1995–2005) for all-purpose and system-specific drugs according to educational status and income in a 5% population-based sample (137 300) and a population of Danish twins (n=24 370), showing results from unpaired and intrapair analyses stratified on zygosity
| Unpaired analysis* |
Intrapair analysis† |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 5% Population n=137 300 |
Twins DZSS n=15 788 | MZ n=8582 |
DZSS |
MZ |
||||||
| Type of drug | MR | 95% CI | MR | 95% CI | MR | 95% CI | MR | 95% CI | MR | 95% CI |
| All purpose | ||||||||||
| Education | ||||||||||
| Secondary | 0.90 | 0.90 to 0.90 | 0.90 | 0.86 to 0.95 | 0.87 | 0.81 to 0.93 | 0.88 | 0.84 to 0.93 | 0.97 | 0.91 to 1.03 |
| Tertiary | 0.82 | 0.82 to 0.83 | 0.85 | 0.80 to 0.91 | 0.83 | 0.76 to 0.90 | 0.86 | 0.80 to 0.92 | 0.95 | 0.86 to 1.05 |
| Income | ||||||||||
| 2nd quartile | 0.78 | 0.78 to 0.78 | 0.81 | 0.76 to 0.85 | 0.81 | 0.75 to 0.88 | 0.86 | 0.82 to 0.91 | 0.91 | 0.85 to 0.97 |
| 3rd quartile | 0.72 | 0.72 to 0.73 | 0.72 | 0.69 to 0.77 | 0.74 | 0.69 to 0.80 | 0.79 | 0.75 to 0.83 | 0.87 | 0.81 to 0.94 |
| 4th quartile | 0.70 | 0.70 to 0.70 | 0.71 | 0.67 to 0.75 | 0.70 | 0.65 to 0.77 | 0.76 | 0.72 to 0.81 | 0.87 | 0.81 to 0.94 |
| Circulatory system (ATC-C) | ||||||||||
| Education | ||||||||||
| Secondary | 0.95 | 0.95 to 0.96 | 0.92 | 0.85 to 0.99 | 0.87 | 0.78 to 0.96 | 0.85 | 0.79 to 0.92 | 0.89 | 0.81 to 0.97 |
| Tertiary | 0.79 | 0.79 to 0.80 | 0.78 | 0.71 to 0.87 | 0.70 | 0.60 to 0.82 | 0.80 | 0.71 to 0.90 | 0.93 | 0.79 to 1.08 |
| Income | ||||||||||
| 2nd quartile | 0.91 | 0.90 to 0.91 | 0.94 | 0.87 to 1.03 | 0.94 | 0.84 to 1.06 | 1.08 | 0.99 to 1.17 | 0.95 | 0.87 to 1.05 |
| 3rd quartile | 0.83 | 0.83 to 0.84 | 0.86 | 0.78 to 0.94 | 0.86 | 0.76 to 0.97 | 0.97 | 0.89 to 1.06 | 0.98 | 0.89 to 1.08 |
| 4th quartile | 0.79 | 0.79 to 0.79 | 0.82 | 0.74 to 0.90 | 0.85 | 0.74 to 0.97 | 0.97 | 0.88 to 1.08 | 0.94 | 0.84 to 1.05 |
| Nervous system (ATC-N) | ||||||||||
| Education | ||||||||||
| Secondary | 0.80 | 0.80 to 0.80 | 0.87 | 0.79 to 0.96 | 0.77 | 0.67 to 0.88 | 0.85 | 0.77 to 0.94 | 1.00 | 0.86 to 1.17 |
| Tertiary | 0.71 | 0.71 to 0.71 | 0.77 | 0.67 to 0.88 | 0.75 | 0.61.0.92 | 0.78 | 0.67 to 0.90 | 0.91 | 0.73 to 1.16 |
| Income | ||||||||||
| 2nd quartile | 0.61 | 0.60 to 0.61 | 0.61 | 0.55 to 0.68 | 0.60 | 0.52 to 0.70 | 0.68 | 0.61 to 0.75 | 0.75 | 0.67 to 0.87 |
| 3rd quartile | 0.49 | 0.49 to 0.50 | 0.47 | 0.43 to 0.53 | 0.47 | 0.39 to 0.56 | 0.54 | 0.48 to 0.61 | 0.59 | 0.50 to 0.70 |
| 4th quartile | 0.44 | 0.44 to 0.44 | 0.45 | 0.40 to 0.51 | 0.42 | 0.35 to 0.50 | 0.50 | 0.45 to 0.57 | 0.60 | 0.50 to 0.71 |
| Respiratory system (ATC-R) | ||||||||||
| Education | ||||||||||
| Secondary | 0.86 | 0.85 to 0.86 | 0.77 | 0.67 to 0.87 | 0.82 | 0.69 to 0.98 | 0.83 | 0.72 to 0.94 | 1.00 | 0.84 to 1.21 |
| Tertiary | 0.81 | 0.80 to 0.81 | 0.79 | 0.68 to 0.92 | 0.76 | 0.61 to 0.95 | 0.80 | 0.66 to 0.97 | 0.77 | 0.58 to 1.03 |
| Income | ||||||||||
| 2nd quartile | 0.76 | 0.75 to 0.76 | 0.76 | 0.66 to 0.87 | 0.79 | 0.65 to 0.98 | 0.86 | 0.75 to 0.99 | 1.04 | 0.86 to 1.25 |
| 3rd quartile | 0.68 | 0.68 to 0.69 | 0.74 | 0.64 to 0.86 | 0.69 | 0.57 to 0.85 | 0.85 | 0.73 to 0.98 | 1.02 | 0.84 to 1.24 |
| 4th quartile | 0.63 | 0.63 to 0.63 | 0.69 | 0.59 to 0.81 | 0.64 | 0.52 to 0.79 | 0.83 | 0.71 to 0.96 | 1.25 | 1.04 to 1.51 |
| Alimentary tract and metabolism (ATC-A) | ||||||||||
| Education | ||||||||||
| Secondary | 0.84 | 0.84 to 0.84 | 0.85 | 0.77 to 0.94 | 0.81 | 0.71 to 0.93 | 0.84 | 0.75 to 0.94 | 0.98 | 0.85 to 1.14 |
| Tertiary | 0.68 | 0.67 to 0.68 | 0.72 | 0.62 to 0.83 | 0.64 | 0.53 to 0.77 | 0.81 | 0.68 to 0.96 | 0.94 | 0.76 to 1.17 |
| Income | ||||||||||
| 2nd quartile | 0.74 | 0.74 to 0.75 | 0.73 | 0.65 to 0.81 | 0.83 | 0.72 to 0.96 | 0.85 | 0.76 to 0.96 | 0.88 | 0.77 to 1.01 |
| 3rd quartile | 0.64 | 0.64 to 0.65 | 0.63 | 0.56 to 0.71 | 0.77 | 0.66 to 0.90 | 0.77 | 0.68 to 0.87 | 0.87 | 0.75 to 1.02 |
| 4th quartile | 0.61 | 0.61 to 0.61 | 0.60 | 0.53 to 0.68 | 0.65 | 0.55 to 0.77 | 0.76 | 0.67 to 0.88 | 0.86 | 0.72 to 1.02 |
*Unpaired analysis treating twins as individuals while taking interdependence of observations within each individual and within twin pairs into account. The interpretation of MR is the ratio of the mean number of prescriptions at a given time of, for example, an individual with a secondary or tertiary education compared with a random individual with a primary education. MRs are adjusted for age and sex. Income and education are mutually adjusted.
†Intrapair analysis of twins. The interpretation of MR is the ratio of the mean number of prescriptions at a given time of a twin with a secondary or tertiary education compared with its co-twin with a primary education.
Italic typography indicates statistical significance at 5% level.
ATC, Anatomical Therapeutic Chemical classification system; DZSS, dizygotic same sex twins; MZ, monozygotic twins.