outcome

health

indicators

USING HOSPITAL ADMISSION RATES AS A HEALTH OUTCOME INDICATOR: STATISTICAL EXEMPLARS

Roberts SE, Mason A, Goldacre MJ, Yeates D, Gill LE

Report to the Department of HealthSeptember 2000

USING HOSPITAL ADMISSION RATES AS A HEALTH OUTCOME INDICATOR

Statistical exemplars

1. Introduction

2. Myocardial infarction

3. Coronary heart disease

4. Stroke

5. Fractured neck of femur

6. Diabetes

7. Asthma

8. Conclusions

1

1. INTRODUCTION Background For many years admission rates have been used as an outcome indicator to make comparisons over time and between populations. They were considered to be a potential indicator in five of the ten health outcome indicator reports published by NCHOD in 1999. In view of the continuing importance of mortality rates, the Department of Health commissioned NCHOD (Oxford) to prepare a digest of statistical exemplars based on the recommendations about mortality indicators included in the condition specific reports. This report contains statistical exemplars of hospital admission rates for:

• myocardial infarction • coronary heart disease • stroke • fractured neck of femur • diabetes • asthma.

The illustrative values have been derived from the Oxford Record Linkage Database. The definition descriptions are taken from the relevant condition specific reports. Objective The objective of producing these exemplars has been, for each condition, to show:

• age/sex group differences • comparisons between episode-based and person-based admission rates • comparisons of admission rates between health authorities.

2

2. MYOCARDIAL INFARCTION ILLUSTRATIVE VALUES

Methods The indicator definition recommended in the Report is, for a given population, age group and sex; the number of hospital admissions due to myocardial infarction per 100,000 resident population. The ICD code used was ICD-9 410. The objectives of the study were to analyse using the recommended indicator specification:

· age/sex group differences · trends in admission rates over time in recent years · comparisons between episode-based and person-based admission rates · comparisons in admission rates between health authorities.

The illustrative indicator values are based on the Oxford Record Linkage Study data for the five year study period from 1 January 1994 to 31 December 1998. All immediate (emergency and accidental) admissions have been included where the condition was listed anywhere on the hospital record. Comparisons of admission rates have been made between three health authorities. The analysis has involved calculating admission rates in two different ways:

· episode-based admission rates when all admissions for the condition are included

· person-based admission rates when only one admission for the condition each year is included regardless of how many admissions have been made.

Results Hospital admission rates for myocardial infarction for each age group and both sexes are presented in Exhibit 2.1 according to the episode-based and person-based definitions. Also included is the ratio of the total number of individual admissions or episodes for myocardial infarction to the total number of people who were affected. Both sets of age-specific admission rates for myocardial infarction increased steadily with increasing age and were higher among men than women. However, the increased relative risk of admission among men decreased with age. For example, among subjects aged 40-49 the men were about five times more likely than women to be admitted, while for subjects aged over 80 the relative risk dropped to about two. The ratios of the number of episode and person-based episodes were similar for both sexes. For all age groups above 30 years and for men and women the ratios ranged from 1.05 to 1.10. This indicates that multiple admissions for the same person and the same cause in the same calendar year accounted for only a small minority of total admissions. Annual episode-based admission rates for myocardial infarction are illustrated in Exhibit 2.2 for three health authorities and for men and women separately. These rates showed little

3

change over the five year time period. However, it is apparent that there were large differences between the respective authorities that were similar for both sexes. For example, for both men and women the admission rates for authority C were approximately 25% greater than for A. Annual person-based admission rates for men and women in the same authorities are shown in Exhibit 2.3. Since multiple admissions accounted for only a small proportion of the total admissions for myocardial infarction, the trends in the person-based admissions were similar to those shown in Exhibit 2.2.

4

Exhibit 2.1 Age and sex-specific admission rates for myocardial infarction (per 100,000 population) in the Oxford Region (1994-1998)

Admission rates (per 100,000) Ratio of Episode-based Person-based Episodes:People Age group Men Women Men Women Men Women < 1 0 4 0 4 1.00 1 - 4 0 0 0 0 5 - 9 0 0 0 0 6 -10 0 0 0 0 11-14 0 0 0 0 15-19 2 0 1 0 1.17 1.00 20-24 3 1 2 1 1.15 1.00 25-29 7 2 7 2 1.03 1.00 30-34 30 4 28 3 1.07 1.06 35-39 70 12 66 12 1.06 1.06 40-44 137 23 129 21 1.07 1.06 45-49 226 44 210 40 1.08 1.10 50-54 367 97 339 90 1.08 1.07 60-64 494 175 465 163 1.06 1.07 65-69 665 290 613 267 1.08 1.09 70-74 818 399 758 372 1.08 1.07 75-79 1017 576 935 523 1.09 1.10 80-84 1158 690 1072 649 1.08 1.06 85+ 1152 726 1085 691 1.06 1.05 All ages

169

94

157

87

1.08

1.07

5

Exhibit 2.2 Episode-based admission rates for myocardial infarction among men and women in three health authorities (per 100,000 population, 1994-1998)

0

50

100

150

200

250

1993 1994 1995 1996 1997 1998 1999

Year

Adm

issi

on R

ate

(per

100

,000

)

A - MenB - MenC - MenA - WomenB - WomenC - Women

Exhibit 2.3 Person-based admission rates for myocardial infarction among men and women in three

health authorities (per 100,000 population, 1994-1998)

0

50

100

150

200

250

1993 1994 1995 1996 1997 1998 1999

Year

Adm

issi

on R

ate

(per

100

,000

)

A - MenB - MenC - MenA - WomenB - WomenC - Women

6

3. CORONARY HEART DISEASE ILLUSTRATIVE VALUES

Methods The indicator definition recommended in the Report is, for a given population, age group and sex; the number of hospital admissions due to coronary heart disease per 100,000 resident population. The ICD codes used were ICD-9 410-414. The objectives of the study were to analyse using the recommended indicator specification:

· age/sex group differences · trends in admission rates over time in recent years · comparisons between episode-based and person-based admission rates · comparisons in admission rates between health authorities.

The illustrative indicator values are based on the Oxford Record Linkage Study data for the five year study period from 1 January 1994 to 31 December 1998. All immediate (emergency and accidental) admissions have been included where the condition was listed anywhere on the hospital record. Comparisons of admission rates have been made between three health authorities. The analysis has involved calculating admission rates in two different ways:

· episode-based admission rates when all admissions for the condition are included · person-based admission rates when only one admission for the condition each

year is included regardless of how many admissions have been made. Results Exhibit 3.1 shows that the hospital admission rates for coronary heart disease increased greatly with age. The age-specific rates were higher among men although the relative risks decreased among the oldest age groups. The age-specific admission rates for coronary heart disease ranged from between three to seven times higher than the corresponding rates for myocardial infarction. While multiple admissions in the same calendar year accounted for only a small minority of total admissions for myocardial infarction, Exhibit 3.1 shows that they were much more prevalent for coronary heart disease. Multiple admissions for coronary heart disease were more common among men than women and decreased among the oldest age groups. Annual episode-based admission rates are illustrated in Exhibit 3.2 for men and women. Unlike myocardial infarction these rates showed evidence of an increase over the study period for both men and women. Health authority C had the highest admission rates. Authority B, that had lower rates than A for myocardial infarction, had higher rates for coronary heart disease. Although multiple admissions accounted for a sizeable proportion of all admissions for coronary heart disease, the trends in the person-based rates shown in Exhibit 3.3 were similar

7

to those for the episode-based rates. All health authorities similarly showed an increase for both sexes in admission rates over time.

8

Exhibit 3.1 Age and sex-specific admission rates for coronary heart disease (per 100,000 population) in the Oxford Region (1994-1998)

Admission rates (per 100,000) Ratio of Episode-based Person-based Episodes:People Age group Men Women Men Women Men Women < 1 27 23 17 15 1.60 1.46 1 - 4 1 1 1 1 1.00 1.25 5 - 9 1 1 1 1 1.67 1.67 6 -10 2 0 1 0 1.40 1.00 11-14 2 3 2 2 1.25 1.22 15-19 9 7 7 5 1.22 1.26 20-24 12 9 9 7 1.35 1.21 25-29 39 17 25 12 1.56 1.48 30-34 164 35 91 23 1.81 1.57 35-39 383 81 209 57 1.83 1.43 40-44 777 171 432 110 1.80 1.56 45-49 1337 365 755 222 1.77 1.64 50-54 2297 662 1282 417 1.79 1.59 60-64 3136 1166 1810 717 1.73 1.63 65-69 4009 1641 2330 1029 1.72 1.59 70-74 4373 2148 2755 1397 1.59 1.54 75-79 5019 2786 3218 1885 1.56 1.48 80-84 5431 3094 3684 2243 1.47 1.38 85+ 5297 3300 3892 2492 1.36 1.32 All ages

944

502

569

337

1.66

1.49

9

Exhibit 3.2 Episode-based admission rates for CHD among men and women in three health authorities (per 100,000 population, 1994-1998)

0

200

400

600

800

1000

1200

1400

1600

1993 1994 1995 1996 1997 1998 1999

Year

Adm

issi

on R

ate

(per

100

,000

)

A - MenB - MenC - MenA - WomenB - WomenC - Women

Exhibit 3.3 Person-based admission rates for CHD among men and women in three

health authorities (per 100,000 population, 1994-1998)

0

100

200

300

400

500

600

700

800

1993 1994 1995 1996 1997 1998 1999

Year

Adm

issi

on R

ate

(per

100

,000

)

A - MenB - MenC - MenA - WomenB - WomenC - Women

10

4. STROKE ILLUSTRATIVE VALUES

Methods The indicator definition recommended in the Report is, for a given population, age group and sex; the number of hospital admissions due to stroke per 100,000 resident population. The ICD codes used were ICD-9 431-438. The objectives of the study were to analyse using the recommended indicator specification:

· age/sex group differences · trends in admission rates over time in recent years · comparisons between episode-based and person-based admission rates · comparisons in admission rates between health authorities.

The illustrative indicator values are based on the Oxford Record Linkage Study data for the five year study period from 1 January 1994 to 31 December 1998. All immediate (emergency and accidental) admissions have been included where the condition was listed anywhere on the hospital record. Comparisons of admission rates have been made between three health authorities. The analysis has involved calculating admission rates in two different ways:

· episode-based admission rates when all admissions for the condition are included · person-based admission rates when only one admission for the condition each

year is included regardless of how many admissions have been made. Results Exhibit 4.1 shows that both the episode and person-based age-specific admission rates for stroke increased greatly with age and were higher in men. The proportions of admissions that were due to multiple admissions in the same calendar year were comparable for the two sexes and among all age groups for which there were relatively large numbers of admissions. For instance, the ratios of episodes to people varied between 1.10 and 1.20 in all age and sex-groups involving subjects aged over 30. The annual episode-based admission rates for the health authorities are shown in Exhibit 4.2. These show evidence of an increase in admission rates for stroke over the time period. However, for authorities A and C there was a reduction in rates from 1994 to 1995. The person-based admission rates for the three authorities in Exhibit 4.3 show similar patterns to the episode-based rates. However, since multiple admissions were relatively infrequent for stroke, this is unsurprising.

11

Exhibit 4.1 Age and sex-specific admission rates for stroke (per 100,000 population) in the Oxford Region (1994-1998)

Admission rates (per 100,000) Ratio of Episode-based Person-based Episodes:People Age group Men Women Men Women Men Women < 1 15 11 15 11 1.00 1.00 1 - 4 3 1 2 1 1.43 1.00 5 - 9 2 2 2 1 1.00 1.40 6 -10 3 2 2 2 1.30 1.43 11-14 2 2 2 2 1.00 1.00 15-19 3 3 3 3 1.00 1.00 20-24 5 6 5 6 1.04 1.13 25-29 5 6 5 5 1.07 1.10 30-34 9 8 8 7 1.14 1.14 35-39 26 17 23 15 1.12 1.13 40-44 51 27 43 23 1.17 1.19 45-49 84 48 75 41 1.13 1.16 50-54 169 88 149 74 1.14 1.19 60-64 298 183 257 159 1.16 1.15 65-69 506 325 434 278 1.16 1.17 70-74 879 601 752 503 1.17 1.19 75-79 1459 1031 1266 899 1.15 1.15 80-84 2208 1755 1912 1549 1.16 1.13 85+ 2751 2267 2434 2053 1.13 1.10 All ages

164

178

142

156

1.15

1.14

12

Exhibit 4.2 Episode-based admission rates for stroke among men and women in three health authorities (per 100,000 population, 1994-1998)

0

50

100

150

200

250

1993 1994 1995 1996 1997 1998 1999

Year

Adm

issi

on R

ate

(per

100

,000

)

A - MenB - MenC - MenA - WomenB - WomenC - Women

Exhibit 4.3 Person-based admission rates for stroke among men and women in three health

authorities (per 100,000 population, 1994-1998)

0

50

100

150

200

250

1993 1994 1995 1996 1997 1998 1999

Year

Adm

issi

on R

ate

(per

100

,000

)

A - MenB - MenC - MenA - WomenB - WomenC - Women

13

5. FRACTURED FEMUR ILLUSTRATIVE VALUES

Methods The indicator definition recommended in the Report is, for a given population, age group and sex; the number of hospital admissions due to fractured femur per 100,000 resident population. The ICD codes used were ICD-9 820-821. The objectives of the study were to analyse using the recommended indicator specification:

· age/sex group differences · trends in admission rates over time in recent years · comparisons between episode-based and person-based admission rates · comparisons in admission rates between health authorities.

The illustrative indicator values are based on the Oxford Record Linkage Study data for the five year study period from 1 January 1994 to 31 December 1998. All immediate (emergency and accidental) admissions have been included where the condition was listed anywhere on the hospital record. Comparisons of admission rates have been made between three health authorities. The analysis has involved calculating admission rates in two different ways:

· episode-based admission rates when all admissions for the condition are included

· person-based admission rates when only one admission for the condition each year is included regardless of how many admissions have been made.

Results Exhibit 5.1 shows that admission rates for fractured femur were very low for most age groups. However, they increased greatly with age among subjects, particularly women, who were aged over 70. The low ratios of episodes to people for both sexes indicate that multiple admissions for the same person in the same calendar year accounted for only a small minority of total admissions for fractured femur. The annual trends in both episode and person-based admission rates in the three health authorities were very similar as shown in Exhibits 5.2 and 5.3. However, since multiple admissions were particularly infrequent for fractured femur, this is unsurprising. There were no clear upward or downward trends in admission rates for the three authorities. Nonetheless, there was a fair amount of variability in the admission rates for fractured femur between them. For example, the rates for women in authority C were in some years about one-third higher than for B.

14

Exhibit 5.1 Age and sex-specific admission rates for fractured femur (per 100,000 population) in the Oxford Region (1994-1998)

Admission rates (per 100,000) Ratio of Episode-based Person-based Episodes:People Age group Men Women Men Women Men Women < 1 100 83 100 82 1.00 1.01 1 - 4 38 13 37 13 1.01 1.04 5 - 9 17 10 17 10 1.03 1.07 6 -10 22 11 21 10 1.02 1.12 11-14 33 6 33 6 1.03 1.00 15-19 25 6 23 6 1.05 1.00 20-24 18 5 16 4 1.17 1.09 25-29 15 4 14 4 1.02 1.00 30-34 13 4 13 4 1.08 1.00 35-39 14 7 13 7 1.05 1.13 40-44 18 10 18 10 1.04 1.07 45-49 23 21 23 21 1.01 1.02 50-54 25 47 25 45 1.00 1.06 60-64 40 92 39 89 1.04 1.04 65-69 81 160 73 152 1.12 1.05 70-74 154 350 149 339 1.04 1.03 75-79 315 782 302 746 1.04 1.05 80-84 636 1486 609 1421 1.05 1.05 85+ 1300 2628 1253 2504 1.04 1.05 All ages

54

150

52

143

1.04

1.05

15

Exhibit 5.2 Episode-based admission rates for fractured femur among men and women in three health authorities (per 100,000 population, 1994-1998)

0

40

80

120

160

200

1993 1994 1995 1996 1997 1998 1999

Year

Adm

issi

on R

ate

(per

100

,000

)

A - MenB - MenC - MenA - WomenB - WomenC - Women

Exhibit 5.3 Person-based admission rates for fractured femur among men and women in three

health authorities (per 100,000 population, 1994-1998)

0

40

80

120

160

200

1993 1994 1995 1996 1997 1998 1999

Year

Adm

issi

on R

ate

(per

100

,000

)

A - MenB - MenC - MenA - WomenB - WomenC - Women

16

6. DIABETES ILLUSTRATIVE VALUES

Methods The indicator definition recommended in the Report is, for a given population, age group and sex; the number of hospital admissions due to diabetes per 100,000 resident population. The ICD code used was ICD-9 250. The objectives of the study were to analyse using the recommended indicator specification:

· age/sex group differences · trends in admission rates over time in recent years · comparisons between episode-based and person-based admission rates · comparisons in admission rates between health authorities.

The illustrative indicator values are based on the Oxford Record Linkage Study data for the five year study period from 1 January 1994 to 31 December 1998. All immediate (emergency and accidental) admissions have been included where the condition was listed anywhere on the hospital record. Comparisons of admission rates have been made between three health authorities. The analysis has involved calculating admission rates in two different ways:

· episode-based admission rates when all admissions for the condition are included · person-based admission rates when only one admission for the condition each

year is included regardless of how many admissions have been made. Results Exhibit 6.1 shows that admission rates for diabetes were higher in men in all age groups over 30. Multiple admissions for diabetes in the same calendar year were common. The ratios of episodes to people ranged from between 1.25 and 1.40 for subjects in all age groups over 25 and were comparable between men and women. The episode-based admission rates increased substantially over the time period as shown in Exhibit 6.2. These increases were slightly greater for men than women and were most pronounced for health authority C. For example, the episode-based admission rate for men in authority C more than doubled from 167 per 100,000 in 1994 to 366 in 1998. The corresponding increases for authorities A and B were 89% and 68%. Among women the percentage increases in episode-based admission rates for authorities A, B and C (at 68%, 53% and 74% respectively) were slightly lower. Although multiple admissions were relatively prevalent for diabetes, similar trends were apparent for person-based admissions in the authorities as shown in Exhibit 6.3. Nonetheless, the increases in the person-based rates were slightly lower than for the episode-based admissions. Exhibit 6.1 Age and sex-specific admission rates for diabetes (per 100,000 population) in

17

the Oxford Region (1994-1998) Admission rates (per 100,000) Ratio of Episode-based Person-based Episodes:People Age group Men Women Men Women Men Women < 1 31 23 23 20 1.35 1.12 1 - 4 20 21 14 17 1.44 1.22 5 - 9 40 51 33 36 1.19 1.39 6 -10 97 78 57 46 1.71 1.67 11-14 60 88 41 50 1.45 1.76 15-19 53 88 43 55 1.24 1.59 20-24 57 69 38 47 1.50 1.46 25-29 51 69 40 48 1.26 1.42 30-34 67 61 53 44 1.26 1.37 35-39 110 72 79 51 1.38 1.40 40-44 137 77 97 58 1.40 1.33 45-49 188 137 144 98 1.30 1.40 50-54 330 213 237 161 1.39 1.32 60-64 545 402 402 296 1.36 1.36 65-69 727 535 536 403 1.36 1.33 70-74 984 754 703 545 1.40 1.38 75-79 1302 1003 939 751 1.39 1.34 80-84 1632 1273 1212 980 1.35 1.30 85+ 1638 1138 1269 896 1.29 1.27 All ages

223

217

163

160

1.37

1.36

18

Exhibit 6.2 Episode-based admission rates for diabetes among men and women in three health authorities (per 100,000 population, 1994-1998)

0

50

100

150

200

250

300

350

400

1993 1994 1995 1996 1997 1998 1999

Year

Adm

issi

on R

ate

(per

100

,000

)

A - MenB - MenC - MenA - WomenB - WomenC - Women

Exhibit 6.3 Person-based admission rates for diabetes among men and women in three health

authorities (per 100,000 population, 1994-1998)

0

50

100

150

200

250

300

350

400

1993 1994 1995 1996 1997 1998 1999

Year

Adm

issi

on R

ate

(per

100

,000

)

A - MenB - MenC - MenA - WomenB - WomenC - Women

19

7. ASTHMA ILLUSTRATIVE VALUES

Methods The indicator definition recommended in the Report is, for a given population, age group and sex; the number of hospital admissions due to asthma per 100,000 resident population. The ICD code used was ICD-9 493. The objectives of the study were to analyse using the recommended indicator specification:

· age/sex group differences · trends in admission rates over time in recent years · comparisons between episode-based and person-based admission rates · comparisons in admission rates between health authorities

The illustrative indicator values are based on the Oxford Record Linkage Study data for the five year study period from 1 January 1994 to 31 December 1998. All immediate (emergency and accidental) admissions have been included where the condition was listed anywhere on the hospital record. Comparisons of admission rates have been made between three health authorities. The analysis has involved calculating admission rates in two different ways:

· episode-based admission rates when all admissions for the condition are included · person-based admission rates when only one admission for the condition each

year is included regardless of how many admissions have been made. Results Exhibit 7.1 shows that the age-specific admission rates for asthma, unlike all the other conditions considered in this Report, were highest among children aged under five. For both sexes the rates were lowest among subjects aged 20-64 and increased gradually to the 80-84 age group. The asthma admission rates were higher among boys than girls aged under five and higher in females than males in all other age groups with the exception of the two oldest age groups where the rates were more comparable. Multiple admissions for asthma were most common among children aged under five. There was a large amount of variation in the age-specific multiple admission ratios. The episode-based admission rates for men and women in the three authorities in Exhibit 7.2 show patterns of divergence in recent years. In 1994 the six admission rates were found to lie within 180 and 220 per 100,000. By 1998 the range had spread from 131 to 302 per 100,000. In particular, there were increasing admission rates in authority C and reductions for A. Although multiple admission patterns were somewhat variable across the different sex and age groupings, the trends for person-based admission rates shown in Exhibit 7.3 were similar to the episode-based. There were again increasing rates for authority C and decreases for A.

20

Exhibit 7.1 Age and sex-specific admission rates for asthma (per 100,000 population) in the

Oxford Region (1994-1998) Admission rates (per 100,000) Ratio of Episode-based Person-based Episodes:People Age group Men Women Men Women Men Women < 1 2131 1058 1708 867 1.25 1.22 1 - 4 602 361 484 291 1.24 1.24 5 - 9 258 148 221 135 1.16 1.09 6 -10 177 164 145 121 1.22 1.35 11-14 118 213 98 163 1.20 1.31 15-19 87 227 76 180 1.14 1.26 20-24 82 178 71 132 1.15 1.36 25-29 71 147 62 111 1.15 1.32 30-34 55 133 50 112 1.11 1.19 35-39 76 120 58 99 1.30 1.22 40-44 73 127 60 101 1.21 1.25 45-49 76 135 65 105 1.17 1.29 50-54 113 164 96 135 1.18 1.21 60-64 120 184 104 158 1.15 1.17 65-69 143 220 127 184 1.13 1.20 70-74 192 225 168 196 1.14 1.15 75-79 208 244 184 216 1.13 1.13 80-84 247 242 225 223 1.10 1.09 85+ 219 215 210 193 1.04 1.11 All ages

170

192

142

156

1.19

1.23

21

Exhibit 7.2 Episode-based admission rates for asthma among men and women in three health authorities (per 100,000 population, 1994-1998)

0

50

100

150

200

250

300

350

1993 1994 1995 1996 1997 1998 1999

Year

Adm

issi

on R

ate

(per

100

,000

)

A - MenB - MenC - MenA - WomenB - WomenC - Women

Exhibit 7.3 Person-based admission rates for asthma among men and women in three health

authorities (per 100,000 population, 1994-1998)

0

50

100

150

200

250

300

350

1993 1994 1995 1996 1997 1998 1999

Year

Adm

issi

on R

ate

(per

100

,000

)

A - MenB - MenC - MenA - WomenB - WomenC - Women

22

8. CONCLUSIONS

Myocardial infarction Both sets of age-specific admission rates for myocardial infarction increased steadily with increasing age and were higher among men than women. However, the increased relative risk of admission among men decreased with age. For example, among subjects aged 40-49 the men were about five times more likely than women to be admitted. For subjects aged over 80 the relative risk had dropped to about two. The ratios of the number of episode and person-based episodes were similar for both sexes. For all age groups above 30 years and for men and women the ratios ranged from 1.05 to 1.10. This indicates that multiple admissions for the same person and the same cause in the same calendar year accounted for only a small minority of total admissions. Annual episode-based admission rates for myocardial infarction showed little change over the time period. However, it is apparent that there were large differences between the respective health authorities that were similar for both sexes. For example, for men and women the admission rates for authority C were approximately 25% greater than for A. Annual person-based admission rates for men and women in the authorities were similar to the episode-based ones as multiple admissions accounted for only a small proportion of the total admissions for myocardial infarction. Coronary heart disease The admission rates for coronary heart disease also increased greatly with age. The age-specific rates were higher among men although the relative risks, as with myocardial infarction, decreased among the oldest age groups. The age-specific admission rates for coronary heart disease ranged from between three to seven times higher than the corresponding rates for myocardial infarction. While multiple admissions in the same calendar year accounted for only a small minority of the total admissions for myocardial infarction, they were much more prevalent for coronary heart disease. Multiple admissions for coronary heart disease were more common among men than women and decreased among the oldest age groups, particularly in men. Unlike myocardial infarction, annual episode-based rates showed evidence of an increase over the study period for both men and women. Health authority C had the highest admission rates. Authority B, that had lower rates than A for myocardial infarction, had higher rates for coronary heart disease. Although multiple admissions accounted for a sizeable proportion of all admissions for coronary heart disease, the trends in the person-based rates were similar to those for the episode-based rates. The three health authorities showed an increase in admission rates over time for both sexes. Stroke

23

Both the episode and person-based age-specific admission rates for stroke increased greatly with age and were higher in men than women. The proportions of all admissions that were due to multiple admissions in the same calendar year were comparable for the two sexes and among all age groups for which there were relatively large numbers of admissions. For instance, the ratios of episodes to people varied between 1.10 and 1.20 in all age and sex-groups involving subjects aged over 30. The annual episode-based admission rates for the health authorities increased over the time period. Although there was a reduction in rates from 1994 to 1995 for authorities A and C. The person-based admission rates for the three authorities show similar patterns to the episode-based rates. However, since multiple admissions were relatively infrequent for stroke, this is unsurprising. Fractured femur Hospital admission rates for fractured femur were very low for most age groups. However, they increased greatly with age among subjects, particularly women, who were aged over 70. The low ratios of episodes to people for both sexes indicate that multiple admissions for the same person in the same calendar year accounted for only a small minority of the total admissions for fractured femur. The annual trends in both episode and person-based admission rates in the three health authorities were very similar. However, since multiple admissions were particularly infrequent for fractured femur, this is unsurprising. There were no clear upward or downward trends in admission rates in the three authorities. Nonetheless, there was a fair amount of variability in the admission rates for fractured femur between the three. For example, the rates for women in authority C were in some years about one-third higher than for B. Diabetes Admission rates for diabetes were higher in men than in women in all age groups over 30. Multiple admissions for diabetes in the same calendar year, in comparison to other conditions such as myocardial infarction, stroke and fractured femur, were much more common. The ratios of episodes to people ranged from between 1.25 and 1.40 for subjects in all age groups over 25 and were comparable between men and women. The episode-based admission rates showed substantial increases over the time period. These increases were slightly greater for men than women and were most pronounced for health authority C. For example, the episode-based admission rate for men in authority C more than doubled from 167 per 100,000 in 1994 to 366 in 1998, while the corresponding increases for authorities A and B were 89% and 68%. Among women the percentage increases in episode-based admission rates for authorities A, B and C (68%, 53% and 74% respectively) were slightly lower. Although multiple admissions were relatively prevalent for diabetes, similar trends were apparent for person-based admissions in the three authorities. Nonetheless, the increases in

24

the person-based rates were slightly lower than for the episode-based admissions. The percentage increases in authorities A, B and C were respectively 74%, 63% and 79% for men and 66%, 50% and 60% for women. Asthma The age-specific admission rates for asthma, unlike all the other conditions considered in this Report, were highest among children aged under five. For both sexes the rates were lowest among subjects aged 20-64 and increased gradually until the 80-84 age group. The asthma admission rates were higher among boys under five than girls and were then higher in females than males in all other age groups, with the exception of the two oldest age groups where the rates were comparable. Multiple admissions for asthma were most common among children aged under five and least prevalent among the oldest age group. Unlike most of the other conditions in this Report, there was a large amount of variation in the age-specific multiple admission ratios. The episode-based admission rates for men and women in the three health authorities showed patterns of divergence over the time period. In 1994 the six admission rates were between 180 and 220 per 100,000. By 1998 the range had widened from 131 to 302 per 100,000. In particular, there were increasing admission rates for authority C and reductions for A. Although multiple admission patterns were somewhat variable across the different sex and age groupings, the trends for person-based admission rates were similar to those that were based on episodes. There were again increasing rates for authority C and decreases for A.

25