Diabetologia 9 Springer-Verlag 1983

Transcription

1 Diabetlgia (1983) 24: Diabetlgia 9 Springer-Verlag 1983 Diabetes Mrtality: New Light n an Underestimated Public Health Prblem J. H. Fuller 1, J. Elfrd*, P. Gldblatt 2 and A. M. Adelstein 3 I Department f Cmmunity Medicine, The Middlesex Hspital Medical Schl, Central Middlesex Hspital, 2Office f Ppulatin Censuses and Surveys and 3Department f Medical Statistics and Epidemilgy, The Lndn Schl f Hygiene and Trpical Medicine, Lndn, UK Summary. Mrtality frm diabetes is underestimated fur- t fivefld by methds f analysis f death certificatin data which use nly underlying cause f death. This prblem is partially vercme by cding all cnditins mentined n death certificates. Fr a sample f deaths in England and Wales ver the years , the bserved prprtin f certificates with specific underlying causes f death fr certificates mentining diabetes was cmpared with the expected prprtin fr all certificates. These bserved/expected ratis were significantly increased in each sex fr circulatry diseases and were significantly reduced fr neplasms. Fr 'ne- phritis' they were als increased, especially belw 45 years f age. These results were cnfirmed by an analysis f underlying cause f death in a chrt f nearly 6,000 members f the British Diabetic Assciatin. Of the 2,134 deaths in this chlt, diabetes was nt mentined n 33% f the death certificates. Fr the perid , death rates fr circulatry diseases assciated with diabetes increased by 6% fr males but remained cnstant fr females. Key wrds: Diabetes mrtality, circulatry diseases, ischaemic heart disease, neplasms, nephritis. Diabetes mellitus has becme an increasingly imprtant cause f mrtality and mrbidity in an ageing ppulatin [1], nnetheless it has been called ~ underestimated public health prblem' [2]. This underestimatin ccurs partly because, in mst cuntries, mrtality statistics are based upn the disease cnsidered t be the 'underlying' cause f death and disregard ther, ften re.. lated, diseases diagnsed in the same patient. Anther reasn is that diabetes, being a chrnic disease, is assciated with ther cnditins, such as ischaemic heart disease, which may be mre 'visible' t the certifying physician and thus selected as the underlying cause f death in preference t diabetes. The frequency with which diabetes has been cited as the underlying cause f death has varied cnsiderably with time and place, and diabetes is nt mentined at all n the death certificates f a substantial prprtin f diabetic subjects [3-5]. Analysis f all cnditins mentined n death certificates may give a clearer picture f the magnitude f diabetes mrtality; such data can be used t examine bth the distributin f causes f death assciated with diabetes and their time trends. * Present address: Department f Clinical Epidemilgy and General Practice, The Ryal Free Hspital Medical Schl, Pnd Street, Hampstead, Lndn NW3 2QG, UK Methds All cnditins mentined n death certificates were cded by the Office f Ppulatin Censuses and Surveys (OPCS) fr a randm sample f natinal data fr England and Wales frm 1972 t 1977, excluding The percentage f death certificates cded in this way varied frm 10% in 1972 t 100% in 1975 and 1976, with 25% samples in 1973 and In the present analysis, fr certificates mentining diabetes, bserved frequencies f particular underlying causes f death were cmpared with expected frequencies. As shwn in the Appendix, the rati f bserved t expected prprtins has been calculated excluding certificates with diabetes as the underlying cause f death, and the rati s btained is termed a cnditinal prprtinal registratin rati (CPRR=bserved/expected prprtins xl00). Where the frequency f a specific underlying cause f death amng certificates mentining diabetes is the same as fr the general ppulatin, the CPRR equals 100. The CPRRs fr varius underlying causes f death have been calculated by year f death, sex, and brad age grups. The statistical significance f deviatins f the CPRR frm 100 was calculated using a Chi-squared test n ne degree f freedm [6]. In the calculatin f the CPRR, certificates giving rise t the bserved deaths must have at least tw mentined causes f death, ne f which is diabetes. Hwever, in the calculatin f the expected deaths, all certificates have been used, sme f which nly specify ne cause f death. It has been calculated that CPRRs based n all certificates d nt differ significantly frm thse derived nly frm certificates with tw r mre causes f death mentined n them. Fr certificates mentining diabetes, underlying cause death rates fr circulatry diseases, ischaemic heart disease, diabetes and all causes have been estimated fr the years and the rates age-standardised t the year 1975 [7].

2 J. H. Fuller et al.: Diabetes Mrtality 337 ~q -e-. r cxl ~-, ~q v-. Further infrmatin n mrtality amng diabetic subjects has been btained frm a prspective study f 5,971 members f the British Diabetic Assciatin resident in England and Wales and recruited between 1965 and The chrt cmprised males and 2968 females, f whm 35% and 30% respectively were belw the age f 40 years [8]. Questinnaire respnses frm a sample f 100 f the chrt indicated that 99% f the grup suffered frm diabetes. The study members were 'flagged' at the Natinal Health Service Central Register and the present analysis is based n deaths ccurring t this chrt befre 1 January Causes f death were classified accrding t the eighth revisin f the Internatinal Classificatin f Diseases (ICD). Results [ e- --&..= e. 9 L~ 9._= 0.,~ [,- tt-3 tt%,,--. t-q ~, cq c I t-e5 < < I r ~- t'-- r Z c-i er [ E..~ t-~ r p-. O ee3 re5 O ~ Multiple Causes n Death Certificatin Of a ttal f 1,181,357 death certificates fr England and Wales in 1975 and 1976, 3.7% mentined diabetes (3.1% fr males and 4.3% fr females). Table 1 shws the distributin f underlying causes f death amng certificates mentining diabetes fr 1975 and 1976 cmbined where 100% f certificates were multiple-cause cded. The prprtin f certificates giving diabetes as the underlying cause f death declined with age, frm abut 70% fr deaths under 15 years t just ver 20% fr deaths 65 years and ver. Fr persns ver 45 years, circulatry diseases cmprised just ver 50% f underlying causes f death. There were n majr sex differences in these prprtins fr any age grup. The CPRRs fr selected underlying causes f death are shwn in Table 2 fr the years 1975 and 1976 cmbined. Fr all circulatry diseases, CPRRs were significantly greater than 100 in bth sexes and all age grups, being particularly high fr ages 15-44years. Wmen aged years had cnsiderably higher CPRRs fr ischaemic heart disease cmpared t men, whereas CPRRs fr cerebrvascular disease were higher in men than wmen fr all except the lwest age grup. The CPRRs fr all neplasms were significantly lwer than 100 fr men and fr wmen. A ntable exceptin was pancreatic cancer where the CPRR fr men was 117 (p < 0.05), but nt significantly different frm 100 fr wmen. CPRRs were als significantly lwer than 100 fr brnchitis fr all age grups except the yungest, whereas all the CPRRs fr pneumnia were significantly increased. Fr 'nephritis' (ICD ) the CPRRs were cnsistently increased and were particularly high fr the age range years, althugh numbers f expected deaths were small. The variatin in age-adjusted death rates fr diabetes as the underlying cause f death ver the perid is shwn fr males and females separately in Figure 1. Rates have remained steady fr males but have fallen by 19% fr females ver the same perid. Fr certificates mentining diabetes, nt just as the underlying cause f death, Figure i als shws underlying cause death rates fr circulatry diseases, ischaemic heart disease and all causes. The death rates fr certificates mentining diabetes are just ver fur times great-

3 338 J.H. Fuller et al.: Diabetes Mrtality Table 2. Cnditinal prprtinal registratin ratis by selected underlying causes f death ( ) (Excluding certificates with diabetes as underlying cause) Cause ICD a Age (years) All ages cde (Ttal number f deaths) (8th revisin) M F M F M F M F All circulatry diseases d 253 d 138 d 191 d 123 d 119 d 1270 (9,251) 125 d (13,168) Ischaemic heart disease d 473 d 130 d 231 d 123 d 130 d 125 d (5,491) 140 d (6,372) Cerebrvascular disease d 237 d 173 d 145 d 124 d 152 d (2,280) 127 d (4,110) Otherheart disease b d 170 d 113 d d (635) 102 (1,184) All neplasms d 30 d 45 d 28 d 53 d 46 d 51 d (1,641) 41 d (1,494) All respiratry diseases d 226 d 9] (2,291) 104 (2,939) Pneumnia d 322 b d 133 d d (1,544) 115 d (2,338) Brnchitis b 136 b 45 d 49 d 53 d 64 d 52 d (495) 62 d (261) Nephritis b 277 b 16V 203 d 177 d 148 d 185 d (135) 159 d (150) All causes 100 t (ttal number f deaths) (178) (112) (2,958) (2,291) (10,982) (16,627) (14,125) (19,040) a Internatinal Classificatin f Diseases; b expected number f certificates < 5; significance f deviatin f CPRR frm 100:- c p < 0.05, d p < 0.01 ; ttal number f deaths in parentheses er ver the perid than the rates fr diabetes cded as the underlying cause f death and they have risen by 12% fr males and fallen by 6% fr females. Fr persns with diabetes mentined n the death certificate, the changes in underlying cause death rates fr all circulatry diseases were + 6% (males) and 0% (females) and, fr ischaemic heart disease, + 20% (males) and - 7% (females). Study f British Diabetic Assciatin Members The chrt f 5,971 members f the British Diabetic Assciatin has been fllwed up fr mrtality fr between 11 and 14years. Fr deaths ver that perid, 2,134 death certificates were traced and cded fr cause f death. Of these, 1,436 (67%) had diabetes mentined n them, either as the underlying cause r a cntributry cause f death. The distributin f majr underlying causes f death is shwn in Table 3 fr (A) all cded death certificates and (B) thse certificates mentining diabetes. When certificates giving diabetes as the underlying cause were excluded, diabetes was mentined as a cntributry cause n 60% f the remaining 1,742 certificates. This prprtin varied with the underlying cause f death, being highest fr respiratry diseases (69%), and lwest fr accidents (18%). The prprtin fr neplasms (51%) was lwer than that fr circulatry diseases (62%). Mrtality f the British Diabetic Assciatin chrt has been cmpared with that f the general ppulatin f England and Wales fr 1972 by calculating standardised mrtality ratis (bserved/expected deaths x 100) fr specific underlying causes f death by sex and age (Table 4). The standardised mrtality ratis fr all causes, all circulatry diseases and ischaemic heart disease were significantly greater than 100, the values fr wmen being higher than thse fr men fr all age grups. Fr wmen in the British Diabetic Assciatin chrt aged years, the particularly high standardised mrtality rati f 1,145 fr ischaemic heart disease indicates that they are mre than 11 times mre likely t die f ischaemic heart disease than wmen f the general ppulatin in the same age range. The standardised mrtality ratis fr neplasms as a whle were nt significantly different frm 100 fr men r fr wmen. Fr all respiratry diseases, the standardised mrtality ratis were significantly lwer than 100 fr men and higher than 100 fr wmen. Discussin The intrductin f insulin therapy in resulted in a prmpt fall in diabetes death rates in England and Wales fr the age range years [9]. Hwever, Reid and Evans [10] pinted ut that the impact f insulin therapy n the verall mrtality f diabetic patients was slight, since there was little benefit fr the lder age grups where mst deaths ccur. One cnsequence f the prlngatin f the diabetic life, mainly as a result f insulin therapy, has been the grwing cntributin f

4 J. H. Fuller et al.: Diabetes Mrtality 339 I I I I I f 1972 '73 '74 '75 '76 '77 YEAIt FEMALES [ I I [ I I 1979 '73 "/4 '75 '76 '77 Fig 1. Death rates per 10,000 ppulatin fr England and Wales , age-standardised t the year 1975, fr death certificates mentining diabetes and the fllwing underlying causes f death: diabetes (O), i schaemic heart disease (O), all circulatry diseases (zx) and all causes ([]). Internatinal Classificatin f Diseases categries as in tables Table 3. British Diabetic Assciatin chrt : prprtin f death certificates mentining diabetes Underlying cause All cded Death (B) as a death certificates % f (A) certificates mentining (A) diabetes (B) YEAR All circulatry diseases 1, All neplasms All respiratry diseases Accidents Other Ttal (excluding diabetes as an underlying cause) 1,742 1, Diabetes Ttal 2,134 1, macrvascular cmplicatins t mrtality [3, 11]. This changing pattern f diabetic fatality, and the certifying physician's appreciatin f it, have been assciated with substantial changes in mrtality statistics ver the last half century. In England and Wales during the perid , diabetes was classified as the underlying cause f death in 91% f certificates mentining diabetes [9] but in nly 60% in 1939 [12], 33% in 1955 [13], and is nw dwn t 22% fr men and 24% fr wmen. A similar fall in the prprtin f deaths assigned t diabetes as underlying cause was nted in a 26-year fllw-up study f patients attending the Jslin Clinic [14]. Since rutine mrtality statistics nly cnsider the underlying cause f death, this trend has resulted in an increasing underestimatin f the cntributin f diabetes t verall mrtality, particularly fr the middleand lder-age ranges. A clearer picture f the pattern f mrtality in diabetic subjects can be btained by cding all cnditins mentined n death certificates. Data frm England and Wales cnfirm the findings in ther develped cuntries [2, 11, 15] that circulatry diseases are the underlying cause f death in just ver 50% f certificates mentining diabetes. The high tll f circulatry diseases recently reprted fr diabetic patients under the age f 50 years [16] is reflected in the high CPRRs fr ttal circulatry diseases and ischaemic heart disease fr the age range years. The increased cardivascular risk f yunger diabetic wmen, shwn in several studies [17-19], is cnfirmed here by the high CPRRs fr the natinal data and high standardised mrtality ratis fr the British Diabetic Assciatin chrt, and is s far unexplained in terms f established cardivascular risk factrs [31. The relatinship between cerebrvascular disease and diabetes is unclear, with sme studies shwing an increased incidence f strke amngst diabetic subjects and thers nt [3]. The current analysis shws significantly raised CPRRs fr cerebrvascular disease fr all except the lwest age grup fr men (Table 1). Standardised mrtality ratis fr cerebrvascular disease were als increased in the British Diabetic Assciatin chrt (Table 3). The excess risk f the diabetic fr death frm renal disease is well dcumented [3, 11] and cnfirmed by the increased CPRRs fr 'nephritis' fr all age-ranges, but particularly fr the year age grup. The CPRRs fr all respiratry diseases were nt significantly different frm 100 but the crrespnding standardised mrtality ratis were increased fr the wmen in the British Diabetic Assciatin chrt. An excess f deaths due t respiratry infectin in diabetics has been reprted elsewhere [19] and is cnfirmed by the increased CPRRs fr pneumnia in all age grups, but the cntrasting lw CPRRs fr brnchitis have nt previusly been nted. A striking feature f the multiple-cause analysis was the lw CPRRs fr mst cancers. Many previus studies shwing an excess cancer mrtality assciated with diabetes have been criticised by Kessler [20] fr their lax definitins f diabetes and the inadequacy f cntrl grups. Kessler's wn study f a chrt f diabetic patients attending the Jslin Clinic shwed a reduced standardised mrtality rati fr all cancers cmbined in men (particularly cancer f the lung), but nt in wmen, and there was a significantly increased risk f pancreatic cancer fr bth men and wmen [21]. A lwered cancer risk, particularly fr wmen, was als fund in Edinburgh [19], but nt in Birmingham, UK [22]. With an excess f early deaths in diabetic patients frm circulatry diseases, part f the lwered mrtality frm cancer and brnchitis may be due t the phenmenn f 'cmpeting risk', since with a prprtinal analysis, an excess f ne particular underlying cause f death must lead t a deficit in thers. Hwever, this is unlikely t be the whle explanatin f the generally lw CPRRs fr

5 340 J.H. Fuller et al. : Diabetes Mrtality Table 4. British Diabetic Assciatin chrt : standardised mrtality ratis by selected underlying causes f death Cause ICD a Age (years) All ages cde (Number f deaths) (8th revisin) M F M F M F M F All circulatry diseases b 631 b 210 d 319 d 149 d 187 d 164 d (542) Ischaemic heart disease b 1,154 b 384 a 432 d 174 d 257 a 187 d (367) Cerebrvascular disease b 541 b a 138 a 142 a (105) All neplasms b 224 b (132) All respiratry diseases b 667 b d 78 c 158 d 81 c (89) All causes 306 d 525 d 198 d 272 d 138 d 197 d 153 d 209 a (Number f deaths) (43) (34) (255) (166) (717) (914) (1,016) (1,115) 199 a (586) 274 d (346) 142 d (131) 109 (115) 173 ~ (119) a Internatinal Classificatin f Diseases b Expected number f deaths < 5. Significance f deviatin f standardised mrtality rati frm 100:- r p < 0.05, d p< Ttal number f deaths in parentheses cancers and brnchitis since they remain lw even in the ldest age range where the CPRRs fr circulatry diseases have cme significantly clser t 100. The British Diabetic Assciatin chrt analysis als indicates that diabetes may nt be mentined s frequently n death certificates with cancer as the underlying cause (51% versus 60% fr all causes except diabetes). Hwever, this degree f under-reprting des nt seem likely t be the whle explanatin f the generalised lw CPRRs fr cancers which deserves further study. The interpretatin f epidemilgical research based n death certificatin data has been questined by sme [23], mainly in terms f the accuracy f the infrmatin. A recent autpsy study shwed that the underlying cause f death, assigned by the pathlgist, was mentined n the death certificates in 72% f cases [24]. Multiple-cause analysis, where all cnditins mentined n. the certificate, and nt just the underlying cause, are analysed, has bvius advantages fr a cnditin such as diabetes. As a measure f the impact f a disease n the cmmunity, mrtality infrmatin based n death certificatin has several advantages ver clinical chrt studies. These include its relative ease f prcessing, the cmprehensive nature f its data-base and its usefulness fr indicating lng-term trends [25]. The trends f diabetic death rates, even thugh analysed ver a relatively shrt perid, certainly give n indicatin that recent develpments in the management f diabetes, particularly cncern ver the quality f diabetic cntrl [26], are having a rapid impact n diabetic mrtality. What is certain is that diabetes, as a cntributr t verall mrtality, is being underestimated at least fur- r fivefld when reliance is placed n underlying cause f death alne and this emphasizes the need fr cntinued mnitring f all cnditins mentined at death in diabetic subjects. Acknwledgements. JE was supprted by a research grant frm the British Diabetic Assciatin. We thank Miss S. Dlley and Mr. S. Edmeades fr their skilled assistance. References 1. Keen H, Fuller JH (1980) The epidemilgy f diabetes. In: Extn-Smith AN, Caird FI (eds) Metablic and nutritinal disrders in the elderly. Jhn Wright, Bristl, pp Tkuhata GK, Miller W, Dign E, Hartman T (1975) Diabetes mellitus: an underestimated public health prblem. J Chrn Dis 28: West KM (1978) Epidemilgy f diabetes and its vascular lesins. Elsevier, New Yrk 4. Tkuhata GK (1976) Reprt f the wrkgrup n mrtality f the cmmittee n scpe and impact t the Natinal Cmmissin n Diabetes. Natinal Institutes f Health, Bethesda, NIH Publicatin N , 3 (Part 1), pp O'Sullivan JB, Mahan CM (1982) Mrtality related t diabetes and bld glucse levels in a cmmunity study. Am J Epidemil 116: Annitage P (1971) Statistical methds in medical research. Blackwell Scientific Publicatins, Oxfrd 7. Office f Ppulatin Censuses and Surveys (1983) Supplement DH2. Her Majesty's Statinery Office Lndn (in press) 8. Armstrng B, Lea A J, Adelstein AM, Dnvan JW, White GC, Ruttle S (1976) Cancer mrtality and saccharin cnsumptin in diabetics. Br J Prey Sc Med 30: Stcks P (1944) Diabetes mrtality in and sme f the factrs affecting it. J Hyg 43 : , Reid DD, Evans JG (1970) New drugs and changing mrtality frm nn-infectius disease in England and Wales. Br Med Bull 26: Marks HH, Krall LP (1971) Onset, curse, prgnsis and mrtality in diabetes mellitus. In: Marble A, White P, Bradley RF, Krall LP (eds) Jslin's Diabetes Mellitus, llth edn. Lea & Febiger, Philadelphia, pp Registrar General (1947) Registrar General's statistical review f England and Wales fr the years 1938 and Her Majesty's Statinery Office, Lndn 13. Registrar General (1957) Registrar General's statistical review f England and Wales fr the year Part 3: Cmmentary. Her Majesty's Statinery Office, Lndn

6 J. H. Fuller et al.: Diabetes Mrtality Kessler II (1971) Mrtality experience f diabetic patients. A twenty-six year fllw-up study. Am J Med 51: Sasaki A, Kamad K, Hruchi N (1978) A changing pattern f causes f death in Japanese diabetics. Observatins ver fifteen years. J Chrn Dis 31 : Tunbridge WMG (1981) Factrs cntributing t deaths f diabetics under fifty years f age. Lancet 2: Entmacher PS, Rt HF, Marks HH (1964) Lngevity f diabetic patients in recent years. Diabetes 13: Ka-lewski AS, Czyzyk A, Janeczk D, Lpcynski J (1977) Mrtality frm cardivascular disease amng diabetics. Diabetlgia 13: Shenfield GM, Eltn RA, Bhalla IP, Duncan LJP (1979) Diabetic mrtality in Edinburgh. Diabete Metab 5: Kessler II (1971) Cancer and diabetes mellitus. A review f the literature. J Chrn Dis 23 : Kessler II (1970) Cancer mrtality amng diabetics. J Natl Cancer Inst 44: Hayward RE, Lucena BC (1965) An investigatin int the mrtality f diabetics. J Inst Act 91 : Medical Services Study Grup f the Ryal Cllege f Physicians f Lndn (1978) Death certificatin and epidemilgical research. Br Med J 2: Engel LW, Strauchen JA, Chiazze L, Heid M (1980) Accuracy f death certificatin in an autpsied ppulatin with specific attentin t malignant neplasms and vascular diseases. Am J Epidemil 111: Adelstein AM (1978) Death certificatin and epidemilgical research. Br Med J 2: Tchbrutsky G (1978) Relatin f diabetic cntrl t develpment f micr-vascular cmplicatins. Diabetlgia 15: Received: 12 July 1982 and in revised frm: 3 February 1983 Appendix Calculatin f cnditinal prprtinal registratin ratis (CPRR) In this article the cnditinal prprtinal registratin rati (CPRR) fr a specific cause f death is calculated as: (O/E) x 100 where O = bserved number f certificates which are assigned t the cnditin as underlying cause f death and which cntain a mentin f diabetes; E = number expected amng all certificates which cntain a mentin f diabetes (but nt as underlying cause), if it is assumed that such certificates have the same distributin by underlying cause as is fund amng all ther certificates registered in the same year (fr each sex and brad age grup). Thus, frmally, fr each sex and year f registratin: E = sum ver brad age grups f D x (C/T) where D = Number f certificates which mentin diabetes but are nt assigned t diabetes as underlying cause; C=Ttal number f certificates assigned t the cnditin f interest as underlying cause; T = Ttal number f certificates registered excluding thse assigned t diabetes as underlying cause f death. Dr. J. H. Fuller Department f Cmmunity Medicine Central Middlesex Hspital Lndn NW10 7NS, UK