Psychiatric comorbidity as predictor of costs in back pain patients undergoing disc surgery: a longitudinal observational study

Transcription

1 Konnopk et l. BMC Musculoskeletl Disorders 2012, 13:165 RESEARCH ARTICLE Open Access Psychitric comoridity s predictor of in ck pin ptients undergoing disc surgery: longitudinl oservtionl study Alexnder Konnopk 1*, Mrgrit Löner 2, Melnie Lupp 2, Dirk Heider 1,2, Sven Heinrich 1, Steffi Riedel-Heller 2, Hns Jörg Meisel 3, Lutz Günther 4, Jürgen Meixenserger 5 nd Hns-Helmut König 1 Astrct Bckground: Psychitric comoridity is common in ck pin ptients undergoing disc surgery nd increses economic in mny res of helth. The ojective of this study ws to nlyse psychitric comoridity s predictor of direct nd indirect in ck pin ptients undergoing disc surgery in longitudinl study design. Methods: A smple of 531 ck pin ptients ws interviewed fter n initil disc surgery (T0), 3 months (T1) nd 15 months (T2) using the Composite Interntionl Dignostic Interview to ssess psychitric comoridity nd modified version of the Client Sociodemogrphic nd Service Receipt Inventory to ssess resource utiliztion nd lost productivity for 3-month period prior interview. Helth cre utiliztion ws monetrily vlued y unit nd productivity y lour. Costs were nlysed using rndom coefficient models nd ootstrp techniques. Results: Psychitric comoridity ws ssocited with significntly (p < 0.05) incresed direct (+664 Euro) nd indirect (+808 Euro) t T0. The direct cost difference predominntly resulted from medicl helth cre utiliztion nd ws nerly unchnged t T2. Further importnt cost predictors were clinicl vriles like the presence of chronic medicl disese, the numer of previous disc surgeries, nd time nd gender. Conclusion: Psychitric comoridity presents n importnt predictor of direct nd indirect in ck pin ptients undergoing disc surgery, even if ptients do not utilize mentl helth cre. This effect seems to e stle over time. More ttention should e given to psychitric comoridity nd cost-effective tretments should e pplied to tret psychitric comoridity in ck pin ptients undergoing disc surgery to reduce helth cre utiliztion nd ssocited with psychitric comoridity. Keywords: Bck pin, Disc surgery, Psychitric comoridity, Cost, Economic Bckground In industrilized societies, ck pin presents common helth prolem, which is often ssocited with disc hernition [1]. While most ck pin ptients with disc hernition profit from conservtive tretment surgicl interventions re performed in the most severe cses, when pin nd sensory or motor deficits persist under conservtive tretment [2]. It is well known tht ck pin nd ck pin tretment outcome re strongly influenced y psychologicl fctors including psychitric * Correspondence:.konnopk@uke.de 1 Deprtment of Medicl Sociology nd Helth Economics, University Medicl Centre Hmurg-Eppendorf, Hmurg, Germny Full list of uthor informtion is ville t the end of the rticle comoridity [3-5]. Common psychitric comoridities in ck pin ptients with prevlence rtes exceeding prevlence rtes in the generl popultion re ffective disorders, nxiety disorders nd sustnce use/dependency disorders [6,7]. Not only tretment outcome is ssocited with psychitric comoridity, ut lso helth cre. Severl studies hve found ssocitions etween psychitric comoridity nd incresed helth cre for different diseses, like dementi, sustnce use, hert filure or internl diseses [8-11]. In recent study, Holmerg nd Thelin [12] found tht psychitric comoridity is ssocited with incresed helth cre utiliztion in ck pin ptients. However, so fr no study hs nlysed the effect of psychitric 2012 Konnopk et l.; licensee BioMed Centrl Ltd. This is n Open Access rticle distriuted under the terms of the Cretive Commons Attriution License ( which permits unrestricted use, distriution, nd reproduction in ny medium, provided the originl work is properly cited.

2 Konnopk et l. BMC Musculoskeletl Disorders 2012, 13:165 Pge 2 of 10 comoridity on helth cre in ptients undergoing disc surgery in prospective study design. Estimting the of n illness is useful to inform decision mkers out the economic relevnce of helth prolem nd fesile ojectives for interventions. Additionlly, cost-of-illness studies provide input dt for further reserch, in prticulr for studies modelling cost-effectiveness of interventions. In generl, of illness cn e distinguished into direct nd indirect. Wheres direct refer to the monetry vlue of utilized resources (e.g. for hospitl stys, physicin visits or drugs), indirect refer to productivity lost due to moridity or premture mortlity. The im of our study ws to nlyse predictors for direct nd indirect in ck pin ptients undergoing disc surgery, nd in prticulr the effect of psychitric comoridity in prospective study design. Therey, we hypothesised tht psychitric comoridity is connected to incresed direct s well s indirect. Methods Study design nd smple Our study referred to 620 consecutive ck pin ptients who underwent n index tretment of surgery for hernited disc etween April 2007 nd Octoer The study received ethics committee pprovl y the ethics committee of the University of Leipzig. We included ptients who provided informed consent, were etween the ge of 18 nd 55 yers, spoke Germn sufficiently nd hd rdiologicl determined hernited disc of the luml or cervicl spine. Study prticiption ws declined y 86 (14%) of the 620 ptients nd 3 ptients were excluded due to missing dt on psychitric comoridity, resulting in finl smple of 531 ptients. Disc surgery ws either conducted t the Deprtment of Neurosurgery t the University Hospitl of Leipzig (N = 149, 28%), the Deprtment of Neurosurgery t the Hospitl St. Georg, Leipzig (N = 153, 29%) or the Deprtment of Neurosurgery t the Hospitl Bergmnnstrost, Hlle (N = 229, 43%). After disc surgery, ll ptients were offered rehilittion to prepre return to work which ws rejected y 33 ptients (7%) of 485 non-drop-out ptients ville t T1. Included ptients were interviewed fce-to-fce y experienced nd trined psychologists out psychitric comoridity nd helth cre utiliztion pproximtely 3.63 (SD 2.83) dys fter disc surgery (T0). Follow up interviews were conducted 3 months (T1) nd 15 months (T2) post tretment vi telephone. Instruments Socio-demogrphic nd illness-relted vriles As sociodemogrphic vriles, ge, gender, eduction, living sitution, mritl nd employment sttus were ssessed. Ptients were clssified ccording to the type of disc hernition (cervicl or lumr) nd were sked out the numer of previous disc hernitions s well s previous disc surgeries in their cse history. Furthermore, presence nd nture of other chronic medicl diseses were ssessed. Psychitric comoridity We ssessed psychitric comoridity with Germn version of the Composite Interntionl Dignostic Interview (CIDI) [13]. The CIDI is stndrdized, fully structured dignostic interview for the ssessment of mentl disorders tht provides current nd lifetime dignoses ccording to the definitions of ICD-10 nd DSM-IV. For the purpose of our study retrospective 6-month prevlence dt were ssessed t seline. We ssessed the CIDI sections for ffective, nxiety nd sustnce relted disorders s the most common comorid conditions in ckpin ptients, s descried y Härter et l. [14]. Ptients were sked proe questions on core symptoms of these psychitric disorder groups. If such symptom required medicl ttention or ws sufficiently severe to ffect dily life, it ws scored s present, nd more detiled investigtion ws conducted. Finlly, informtion on the onset nd the recent nture of the prticulr cluster of symptoms were ssessed to generte prevlence dt. Resource utiliztion nd loss of productivity At every mesurement, resource utiliztion nd loss of productivity were retrospectively mesured for the preceding three months using stndrdized questionnire tht ws dpted from questionnires used in erlier studies [15-23]. Hence T0 covered 3 month period prior the surgicl intervention, T1 covered the 3 months following the surgicl intervention nd T2 covered 3 month period strting 1 yer fter the surgicl intervention. We ssessed utiliztion of inptient tretment, rehilittion, outptient physicin nd non-physicin services, medicl goods nd dentures, drugs, trnsports to medicl tretment nd informl cre y reltives nd/ or friends. We further ssessed loss of productivity due to sickness sence dys, erly retirement, time spent for tretments nd productivity reduction t work. Ptients were sked to indicte their disese relted productivity reduction t work on scle rnging from no reduction of productivity to unle to work. Cost clcultion Costs were clculted from societl perspective y vluing resource utiliztion y corresponding unit nd productivity losses y ge nd gender specific lour. For index tretment individul hospitl illing informtion were ville nd used to clculte rtes for dignoses relted groups (DRG) [24,25]. Other hospitl

3 Konnopk et l. BMC Musculoskeletl Disorders 2012, 13:165 Pge 3 of 10 tretments nd the post-surgery rehilittion were vlued y hospitl-type specific men rtes per diem [26,27]. Outptient physicin nd non-physicin visits were vlued y type specific per contct [26,28]. Drug were clculted using prices from the Germn ctlogue of drugs red list [29]. For drugs not listed in the red list, s well s medicl goods nd dentures we used mrket prices. Informl cre ws vlued y verge Germn net ernings [26] representing the opportunity of leisure time. Costs for trnsporttion were sked from the ptients, except for cr use which ws vlued y 0.30 Euro per kilometre ccording to the Germn income tx ct [30]. Lost productivity ws vlued y ge nd gender specific gross ernings [31] plus dditionl employer pyments for socil insurnces [32]. Except for medicl goods, dentures nd phrmceuticls not listed in the red list, ll refer to the yer 2007 (yer of mesurement). For medicl goods, dentures nd phrmceuticls not listed in the red list, prices were otined from n internet sed reserch for ctul mrket prices. These prices refer to 2008 nd 2009, corresponding to the specific time point of the serches. Unit originlly estimted efore 2007 were inflted to 2007 vlues using the Germn consumer price index [33] for direct nd the growth rte of ernings in Germny [34] for indirect. Lost to follow up nlyses From the 531 ptients included t T0, 485 (91%) were ville for interviews t T1 nd 286 t T2 (54%). All ptients lost t T1 nd 88 of the ptients lost t T2 were drop outs, wheres 157 of the ptients lost t T2 were not interviewed ecuse of study end. There were no significnt differences etween complete follow up prticipnts (N = 286) nd ptients lost to follow up (N = 245) regrding disc loction, gender, ge, psychitric comoridity, presence of chronic medicl disese, the numer of previous disc hernitions or surgeries, numer of children, eduction, mritl sttus, living sttus or employment sttus t seline. The only significnt (p <.05) difference ws for type of helth cre insurnce with ptients lost to follow up eing more often memers of the sttutory helth insurnce. Missing vlues To e le to clculte overll direct nd indirect for sufficient smple size, we were forced to replce missing vlues for single vriles. Tle 1 shows mximum percentges of missing vlues for single cost ctegories. For most vriles mximum of three percent of vlues ws missed, except for the DRG rtes of index tretment (21% missings) nd the numer of drug pckges used (9.6% missings t T1, 7.0% missings t T2). Missed DRG rtes were replced y the dignosisspecific (luml or cervicl) men. Due to the very lrge heterogeneity of drugs consumed, we decided to sty conservtive nd replced missing numers of drug pckges y vlue of one. For ll other vriles, missing vlues of n indicted utiliztion were replced y the men utiliztion of respective users. If, for exmple, ptient indicted outptient physicin visits ut not the numer of visits, we replced this missing vlue y the verge numer of visits of physicin visitors. Sttisticl nlysis Differences in sociodemogrphic vriles etween ptients with/without psychitric comoridity were nlysed vi t-test nd chi-squre test s pproprite. We used rndom coefficient models to test our hypothesis nd to identify explntory vriles of direct, indirect nd totl. Since cost dt re often chrcterized y nonnormlity nd right-skewness, we used ootstrp techniques (4,000 replictions) to estimte stndrd s [35]. Explntory vriles used were type of disc hernition, psychitric comoridity, time of mesurement, the interction effect of psychitric comoridity nd time, presence of other chronic medicl diseses, the numer of previous disc surgeries, ge, gender, eduction, mritl sttus, living sitution, employment sttus, type of helth insurnce (sttutory helth insurnce or privte helth insurnce) nd the numer of children. In se cse scenrio, we nlysed direct without informl cre (due to the hypothetic nture of informl cre ) nd indirect without reduction of productivity in work (due to limited vlidity of our ssessment method). Anlyses including informl cre nd reduced productivity were conducted s lterntive scenrio. Significnce level ws set t p < Cost were clculted using PASW (PASW Sttistics 18), sttisticl nlyses were performed using STATA (STATA, Relese 10.0). Results Smple chrcteristics Smple chrcteristics re shown in Tle 2. Overll, men ge ws 42.4 yers, 57% of ptients were mle, 16.2% hd psychitric comoridity nd 38.8% hd comorid chronic medicl diseses. On verge, every fifth ptient hd received former disc surgery in the pst. The most prevelnt comoridity ws depression (11%) followed y nxiety disorders (9%) nd sustnce use disorders (2%). There were no relevnt differences in comoridity etween ptients with luml nd ptients with cervicl disc hernition. We found severl sttisticlly significnt differences etween ptients with nd without psychitric comoridity. Overll, ptients with psychitric comoridity were more often femle, single, living lone, were more often unemployed nd memers of sttutory helth insurnce. Further, in luml disc hernition ptients with psychitric

4 Konnopk et l. BMC Musculoskeletl Disorders 2012, 13:165 Pge 4 of 10 Tle 1 Missing vlues of resource utiliztion T0 T1 T2 N Mx % missings N Mx % missings N Mx % missings Hospitl fee dt for DRG clcultion of index tretment Other hospitl relted vriles Rehilittion relted vriles Outptient physicin visits Outptient non-physicin visits Numer of drug units consumed 1, Medicl goods consumed Informl cre relted vriles Trnsports relted vriles Loss of productivity relted vriles numer nd percentge refer to the overll numer of drug lels reported; percentge refers to the numer of employed. comoridity hd sttisticlly significnt more previous disc hernition thn ptients without psychitric comoridity. Costs Overll, men 3-month direct were 5,403 Euro (SD: 2,238 Euro) t T0, 2,862 Euro (SD: 1,932 Euro) t T1 nd 811 Euro (SD: 2,191 Euro) t T2, wheres men 3-month indirect were 4,130 Euro (SD: 4,083 Euro) t T0, 6,629 Euro (SD: 4,861 Euro) t T1 nd 1,623 Euro (SD: 3,673 Euro) t T2. The results of our se cse regression nlysis re shown in Tle 3. Direct were strongly predicted y time nd clinicl vriles (disc loction, psychitric comoridity, chronic medicl disese, numer of previous disc surgeries). Time ws the most prominent cost predictor due to chnges in therpy over time (T1: -2,456 Euro; T2: -4,634 Euro). Psychitric comoridity t T0 ws the second strongest predictor of direct (+664 Euro), even stronger thn the presence of chronic medicl disese (+467 Euro). Interction effects of time nd psychitric comoridity t T0 were not sttisticlly significnt for direct. Also with indirect, clinicl vriles like psychitric comoridity t T0 (+808 Euro), chronic medicl disese (+951 Euro) nd the numer of previous disc surgeries (+1,142 Euro) were importnt cost predictors. However, the most importnt cost predictors were employment sttus ( 4,502 Euro if unemployed) nd time (T1: +3,028 Euro; T2: -2,370 Euro). At T1, the interction of time nd psychitric comoridity t T0 reched significnce level for indirect. Here psychitric comoridity t T0 ws ssocited with reduction in indirect ( 1,248 Euro). Further significnt predictors of indirect were the numer of children ( 249 Euro), privte helth insurnce ( 759 Euro) nd gender (+1,572 Euro). For totl psychitric comoridity t T0 (+1,469 euro), chronic medicl disese (+1,417 Euro), the numer of previous disc surgery (+1,645 Euro) nd mle gender (+1,203 Euro) were lmost eqully strong explntory vriles. In the lterntive scenrio with informl cre included in direct nd reduction of productivity in work included in indirect, only few chnges occurred (Tle 4). There were no chnges in signs of ny sttisticl significnt explntory vrile, ut psychitric comoridity ws not significnt predictor of indirect ny more. For oth direct s well s indirect, inclusion of the two dditionl cost ctegories resulted in lrger constnt, nd in prtilly lrger effects in prticulr of employment sttus nd gender. Discussion The im of this study ws to investigte whether psychitric comoridity predicts direct nd indirect cost in ck pin ptients undergoing disc surgery nd to estimte other predictors for direct nd indirect, in prospective study design. Summrized, we found tht direct s well s indirect were strongly predicted y time nd clinicl vriles including psychitric comoridity. We found tht psychitric comoridity is ssocited with incresed direct, though we found lmost no mentl helth cre utiliztion t ll mesurements, i.e. psychitric comoridity incresed non-mentl helth cre utiliztion, which hs lso een found in other diseses [8-11]. There re severl possile explntions for this finding. One my e, tht psychitric comoridity is often either not dignosed or not treted with psychitric services, s shown in other studies [36,37]. Another possile explntion my e underreporting of this specific type of helth cre due to fer of stigm. Finlly, stigm my lso e reson why ptients do not utilize psychitric tretment. As result of the therpeutic pthwy, time ws very strong predictor of. At T0 direct were strongly

5 Tle 2 Smple chrcteristics t T0 Without psychitric comoriditiy (N = 445) Overll (N = 531) Luml disc (N = 419) Cervicl disc (N = 112) With psychitric comoridity (N = 86) Age (men (SD)) 42.6 (7.87) 41.4 (8.34) Numer of children (men 1.41 (0.98) 1.43 (2.28) (SD) Numer of previous disc hernitions (men (SD)) Numer of previous disc surgery (men (SD)) 1.61 (1.62) 2.70 (10.3) 0.22 (0.58) 0.29 (0.62) Without psychitric comoriditiy (N = 352) With psychitric comoridity (N = 67) 41.8 (8.05) 40.5 (8.78) 1.37 (1.00) 1.13 (0.99) 1.64 (1.73) 3.00 (11.6) 0.22 (0.58) 0.37 (0.68) * Without psychitric comoriditiy (N = 93) With psychitric comoridity (N = 19) 45.5 (6.35) 44.6 (5.63) 1.55 (0.89) 2.47 (4.41) 1.51 (1.12) 1.59 (1.33) 0.18 (0.57) 0 (0) Psychitric comoridity ICD-10 chpter F0 (N (%)) - 3 (1) - 3 (1) - 0 (0) ICD-10 chpter F1 (N (%)) - 11 (2) - 7 (2) - 4 (4) ICD-10 chpter F3 (N (%)) - 56 (11) - 44 (11) - 12 (11) ICD-10 chpter F4 (N (%)) - 47 (9) - 38 (9) - 9 (8) Self reported chronic medicl disese (N (%)) Yes (ref: No) 170 (38) 36 (42) 229 (65) 45 (67) 46 (49) 5 (26) Gender (N (%) Mle 179 (60) 47 (45) Eduction (N (%)) ISCED level 2 or lower 7 (2) 4 (5) * 214 (61) 32 (48) 6 (2) 4 (6) * 52 (56) 7 (37) 1 (1) 0 (0) ISCED level (69) 57 (66) 240 (68) 48 (72) 66 (71) 9 (47) ISCED level 5 or higher 132 (30) 25 (29) 106 (30) 15 (22) 26 (28) 10 (53) Mritl sttus (N (%)) Mrried (ref: lone) 264 (59) 35 (41) ** 205 (58) 23 (34) *** 59 (63) 12 (63) Living sitution (N (%)) Living lone 68 (15) 24 (28) ** 53 (15) 19 (28) * 15 (16) 5 (26) ** Konnopk et l. BMC Musculoskeletl Disorders 2012, 13:165 Pge 5 of 10

6 Tle 2 Smple chrcteristics t T0 (Continued) Living with prtner/ 364 (82) 58 (67) 290 (82) 45 (67) 74 (80) 13 (68) prents Other living sitution 13 (3) 4 (5) 9 (3) 3 (4) 4 (4) 1 (%) Employment sttus (N (%)) Employed (ref: unemployed) 371 (83) 54 (63) *** 296 (84) 40 (59) *** 75 (81) 14 (74) Type of helth insurnce (N (%)) Sttutory helth insurnce 381 (86) 81 (94) * 308 (87) 62 (93) 73 (78) 19 (100) Privte helth insurnce 64 (14) 5 (6) 44 (13) 5 (7) 20 22) 0 (0) T-test; Chi-squre test; ISCED: interntionl stndrd clssifiction of eduction; SD: stndrd devition; * p <.05; ** p <.01; *** p <.001. * Konnopk et l. BMC Musculoskeletl Disorders 2012, 13:165 Pge 6 of 10

7 Konnopk et l. BMC Musculoskeletl Disorders 2012, 13:165 Pge 7 of 10 Tle 3 Predictors of direct, indirect nd totl ; se cse scenrio Prmeter Direct Stndrd Indirect Stndrd Totl Stndrd Constnt 4, *** 3, *** 8, *** Dignosis *** Psychitric comoridity * * 1, ** T1 2, *** 3, *** * T1 x psychitric comoridity , * 1, * T2 4, *** 2, *** 6, *** T2 x psychitric comoridity , ,355 1,089 Chronic medicl disese ** *** 1, *** Numer of previous disc surgeries *** 1, *** 1, *** Age (centrlized to men) *** * Gender (ref: femle) ** 1, *** 1, *** Being mrried ISCED eductionl level 3 (ref 2) ISCED eductionl level 5 (ref 2) Living sitution: with prtner (ref: lone) Living sitution: others (ref: lone) ,060 Numer of children * Privte helth insurnce (ref: sttutory helth insurnce) ** * Being not employed (ref: eing employed) , *** 4, *** Model sttistics R2 within R2 etween R2 overll * p <.05; ** p <.01; *** p <.001. influenced y cute disese nd in prticulr y disc surgery resulting in the highest three month helth cre of ll mesurements. Acute disese nd disc surgery were oth lso ssocited with sickness sence cusing high indirect t T0. At T1 direct primrily resulted from inptient rehilittion nd susequent outptient tretments, resulting in considerly lower direct compred to T0. Indirect strongly incresed t T1 due to more sickness sence dys resulting from postopertive sick leve nd inptient rehilittion which lsted severl weeks. At T2 cute tretment nd rehilittion hd een completed nd direct preliminry consisted of outptient tretment, resulting in the lowest three month helth cre of ll periods nlysed. Accordingly, most ptients were ck to work gin nd sickness sence (nd indirect ) declined considerly. Though mostly not significnt, the interction term of time nd psychitric comoridity showed n identicl interesting course over time for direct nd indirect : t T0 ptients with psychitric comoridity showed higher thn ptients without; t T1 this difference diminished, ut ws found gin t T2. In our opinion, this course could e seen s n rtefct resulting from the rther strictly orgnised therpy flow during the 3-month intervl preceding the T1 ssessment. This intervl ws chrcterized y the postopertive therpy nd n inptient rehilittion lsting mostly three to four weeks, which oth re highly stndrdized. On the one hnd this limited ptient s choice of helth cre utiliztion nd thus equlized direct of ptients with nd without psychitric comoridity. On the other hnd, reltive stndrdized durtions of postopertive sick leve nd rehilittion, my lso hve equlized indirect of ptients with nd without psychitric comoridity. However, t T2 this effect of therpy ws not present nymore; hence the impct of psychitric comoridity on direct s well s indirect ws oservle gin. In conclusion the impct of psychitric comoridity on cost seems to hve persisted fter disc surgery nd rehilittion. Besides time nd psychitric comoridity, direct nd indirect were lso significntly ssocited with the numer of previous disc surgeries: the more disc surgeries ptients received in the pst, the higher occurred. Hving multiple disc surgeries indictes worse

8 Konnopk et l. BMC Musculoskeletl Disorders 2012, 13:165 Pge 8 of 10 Tle 4 Predictors of direct, indirect nd totl including monetrily vlued informl cre nd reduced productivity t work Prmeter Direct Stndrd Indirect Stndrd Totl Stndrd Constnt 6, *** 6, *** 13,269 1,176 *** Dignosis * Psychitric comoridity * , * T1 2, *** *** 1, *** T1 x psychitric comoridity , T2 5, *** 3, *** 8, *** T2 x psychitric comoridity , * 1,643 1,133 Chronic medicl disese *** *** 1, *** Numer of previous disc surgeries *** 1, ** 1, *** Age (centrlized to men) *** ** Gender (ref: femle) *** 2, *** 1, *** Being mrried ISCED eductionl level 3 (ref 2) ISCED eductionl level 5 (ref 2) ,009 Living sitution: with prtner (ref: lone) Living sitution: others (ref: lone) ,333 1,233 Numer of children *** Privte helth insurnce (ref: sttutory helth insurnce) ** * Being not employed (ref: eing employed) * 7, *** 6, *** Model sttistics R2 within R2 etween R2 overll * p <.05; ** p <.01; *** p <.001. helth stte, e.g. due to chronic ck pin disese with more severe spine involvement or more complicted surgery conditions. This my result in higher direct due to more tretments nd higher indirect due to more sickness sence. Our regression nlysis showed significnt ssocitions of direct nd indirect with gender. Femle gender ws ssocited with higher direct ut lower indirect. A deeper view into direct showed tht women hd higher in lmost ll cost ctegories for luml nd cervicl disc hernitions regrdless of psychitric comoridity eing present or not. One possile explntion for this finding my e tht women in our smple were in worse helth sttes. Women hd more often comorid chronic medicl conditions (44% vs. 35%) nd received on verge more previous disc surgeries (0.29 vs. 0.19). Both vriles were ssocited with higher direct in the regression nlysis which my prtilly explin the gender effect. For indirect, we interpret the finding of lower in women - t lest in prt - s n rtefct resulting from lower productivities pplied for the monetry vlution of lost productivity time. Interestingly, indirect were significntly (p < 0.05) negtively ssocited with the numer of children nd privte helth insurnce. We interpret these two findings s results of selection is. On the one hnd, one could ssume tht ptients with children hve more pressure to return to work, which my result in reduced indirect. On the other hnd memers of privte helth insurnce tend to e helthier due to risk selection of privte insurers. Further, memers of privte helth insurnce in Germny often ern higher income or re self-employed which oth my e incentives to return to work fst. In our se cse nlysis we excluded direct informl cre nd indirect resulting from reduced productivity t work. Costs of informl cre were excluded ecuse they re somewht hypothetic: informl cre present monetrily vlued cre time of reltives or friends [38]. Thus in contrst to ll other direct no rel money is pid. Insted, informl cre represent

9 Konnopk et l. BMC Musculoskeletl Disorders 2012, 13:165 Pge 9 of 10 the opportunity of leisure time lost y reltives or friends. Productivity reduction t work ws ssessed y ten step Likert scle rnging from no reduction of productivity to unle to work on which ptients were sked to rte themselves. This scle hs not een vlidted yet, therefore we excluded productivity reduction t work from our se cse nlysis too. Including these two cost ctegories in lterntive nlyses primrily resulted in clerly lrger constnts nd lrger effects of employment sttus nd gender ut no fundmentl differences in results like sign chnges. Our sttisticl models explined gret shre of the overll vrince in, with coefficients of delimintion (R 2 ) rnging from 0.34 to One must note tht these high vlues of R 2 re in prt result of pseudovrince generted y the vriles disc loction nd employment sttus. Wheres verge of disc surgery were 3,572 Euro for luml disc hernition, they were 5,618 Euro for cervicl disc hernition. Indirect predominntly occurred in employed ptients resulting in verge 3-month indirect of 5,338 Euro for those employed compred to 1,907 Euro for those unemployed. Thus the reltive high vlues of R 2 generted y our models should e seen with cution. Our study hs some limittions. We found reltive high portions of missing vlues in DRG rtes nd the numer of drug pckges used. DRG coding required complete set of vriles, including hospitl record dt which were often not ville, wheres the high portion of missings for drug pckges my e due to memory effects. Our smple contined ptients with cervicl nd luml disc hernitions, which my is our results. However, disese specific nd sociodemogrphic chrcteristics were similr in oth ptient groups; furthermore we controlled for disc loction in our regression nlysis. Our ssessment of psychitric comoridity ws restricted to the most importnt CIDI sections (ffective, nxiety nd sustnce use disorders) tht represent the most prevlent nd costly psychitric disorders. Further, the ssessment of psychitric comoridity took plce fter the surgicl intervention nd my e influenced y this cute event, resulting in n overestimtion of prevlence rtes. Finlly, some prices were not from our se yer 2007, ecuse no prices for this yer were ville. Insted we were forced to use prices of 2008 nd 2009 for some goods. However, the portion of ffected y this is ws very low und should not hve significnt effect on the results. Implictions for clinicl prctice Our findings imply tht more ttention should e given to psychitric comoridity in the ck pin ptients undergoing disc surgery. Clinicins should e wre of the high prevlence rtes of psychitric comoridity in ck pin ptients, in prticulr in the most severe cses which re treted vi surgery. If pplicle, they should consider the ssessment of psychitric distress nd support of mentl helth professionls [39]. Multimodl dignostic nd therpy pproches tht py ttention to psychitric comoridity my help to improve the outcomes of surgicl therpy nd to reduce the connected to psychitric comoridity. Conclusion We found strong effect of psychitric comoridity on direct s well s indirect in ck pin ptients undergoing disc surgery. Yet utiliztion of psychitric tretments ws negligile. The cost effect of psychitric comoridity decresed during the rehilittion period ut ws present gin t follow up. More ttention should e given to psychitric comoridity in disc surgery ptients nd mentl helth cre services should e offered to these ptients. Competing interest The uthors declre tht they hve no competing interests. Authors contriutions AK clculted nd nlysed the cost dt, prticipted in the interprettion of results nd prepred the mnuscript. MZ nd ML prepred clinicl questionnires, collected dt nd prticipted in the interprettion of results. DH ws the primry sttisticin nd conducted ll finl sttisticl nlyses. SH contriuted to the helth economic study design nd designed the helth economic questionnire. HJM, LG nd JM contriuted to the study design nd recruited study ptients. SRH contriuted to the clinicl study design nd mngement, nd contriuted to the interprettion of results. HHK contriuted to the helth economic study design nd mngement, nd interprettion of results. All uthors red nd pproved the finl mnuscript. Acknowledgement This study hs een supported y the Deprtment of Neurosurgery t the University Hospitl Leipzig, the Division of Neurosurgery Hospitl St. Georg Leipzig nd the Deprtment of Neurosurgery t the Hospitl Bergmnnstrost Hlle (Sle) nd received finncil support y the Deutsche Rentenversicherung Bund (reference numer /31.81). Author detils 1 Deprtment of Medicl Sociology nd Helth Economics, University Medicl Centre Hmurg-Eppendorf, Hmurg, Germny. 2 Institute of Socil Medicine, Occuptionl Helth nd Pulic Helth, University of Leipzig, Leipzig, Germny. 3 Deprtment of Neurosurgery, Berufsgenossenschftliche Kliniken Bergmnnstrost, Hlle (Sle), Germny. 4 Deprtment of Neurosurgery, Hospitl St. Georg ggmh, Leipzig, Germny. 5 Deprtment of Neurosurgery, University of Leipzig, Leipzig, Germny. Received: 12 Septemer 2011 Accepted: 21 August 2012 Pulished: 3 Septemer 2012 References 1. vn Dieen JH, Weinns H, Toussint HM: Frctures of the lumr verterl endplte in the etiology of low ck pin: hypothesis on the custive role of spinl compression in specific low ck pin. Medicl Hypothesis 1999, 53: Krämer J: Bndscheienedingte Erkrnkungen. Stuttgrt: Thieme; Pincus T, Burton AK, Vogel S, Field AP: A systemtic review of psychologicl fctors s predictors of chronicity/disility in prospective cohorts of low ck pin. Spine (Phil P 1976) 2002, 27:E109 E120.

10 Konnopk et l. BMC Musculoskeletl Disorders 2012, 13:165 Pge 10 of Linton SJ: A review of psychologicl risk fctors in ck nd neck pin. Spine (Phil P 1976) 2000, 25: vn der Hulst M, Vollenroek-Hutten MM, Ijzermn MJ: A systemtic review of sociodemogrphic, physicl, nd psychologicl predictors of multidisciplinry rehilittion-or, ck school tretment outcome in ptients with chronic low ck pin. Spine (Phil P 1976) 2005, 30: Zieger M, Schwrz R, König HH, Hrter M, Riedel-Heller SG: Depression nd nxiety in ptients undergoing hernited disc surgery: relevnt ut underreserched - systemtic review. Cent Eur Neurosurg 2010, 71: Demyttenere K, Brufferts R, Lee S, Posd-Vill J, Kovess V, AngermeyerMC,LevinsonD,deGirolmoG,NkneH,MneimnehZ, Lr C, de Grf R, Scott KM, Gureje O, Stein DJ, Hro JM, Bromet EJ, Kessler RC, Alonso J, Von Korff M: Mentl disorders mong persons with chronic ck or neck pin: results from the World Mentl Helth Surveys. Pin 2007, 129: Hochlehnert A, Niehoff D, Herzog W, Lowe B: Elevted of tretment in medicl inptients with psychitric comoridity re not reflected in the Germn DRG-system. Psychother Psychosom Med Psychol 2007, 57: Currn GM, Sullivn G, Willims K, Hn X, Allee E, Kotrl KJ: The ssocition of psychitric comoridity nd use of the emergency deprtment mong persons with sustnce use disorders: n oservtionl cohort study. BMC Emerg Med 2008, 8: Kunik ME, Snow AL, Molinri VA, Menke TJ, Souchek J, Sullivn G, Ashton CM: Helth cre utiliztion in dementi ptients with psychitric comoridity. Gerontologist 2003, 43: Syers SL, Hnrhn N, Kutney A, Clrke SP, Reis BF, Riegel B: Psychitric comoridity nd greter hospitliztion risk, longer length of sty, nd higher hospitliztion in older dults with hert filure. J Am Geritr Soc 2007, 55: Holmerg SA, Thelin AG: Primry cre consulttion, hospitl dmission, sick leve nd disility pension owing to neck nd low ck pin: 12-yer prospective cohort study in rurl popultion. BMC Musculoskelet Disord 2006, 7: Wittchen HU, Pfister E: Instruktionsmnul zur Durchführung von DIA-X Interviews. Swets Test Services, Frnkfurt: Swets & Zeitlinger B.V; Hrter M, Reuter K, Weisser B, Schretzmnn B, Aschenrenner A, Bengel J: A descriptive study of psychitric disorders nd psychosocil urden in rehilittion ptients with musculoskeletl diseses. Arch Phys Med Rehil 2002, 83: Strk R, König HH, Leidl R: Costs of inflmmtory owel disese in Germny. PhrmcoEconomics 2006, 24: Neuuer S, Holle R, Menn P, Grssel E: A vlid instrument for mesuring informl cre time for people with dementi. Int J Geritr Psychitry 2009, 24: Lupp M, Heinrich S, Angermeyer MC, König HH, Riedel-Heller SG: Helthcre ssocited with recognized nd unrecognized depression in old ge. Int Psychogeritr 2008, 20: Lupp M, Heinrich S, Mtschinger H, Hensel A, Luck T, Riedel-Heller SG, König HH: Direct ssocited with mild cognitive impirment in primry cre. Int J Geritr Psychitry 2008, 23: Heinrich S, Lupp M, Mtschinger H, Angermeyer MC, Riedel-Heller SG, König HH: Service utiliztion nd helth-cre in the dvnced elderly. Vlue Helth 2008, 11: Lupp M, Heinrich S, Mtschinger H, Sndholzer H, Angermeyer MC, König HH, Riedel-Heller SG: Direct ssocited with depression in old ge in Germny. J Affect Disord 2008, 105: Becker A, Seitz R, Jcoi E, Leidl R: Cost evlution y ptient questionnire: pilot study of weekly cost diry. Rehilittion (Stuttg) 2001, 40: Rosch M, Leidl R, Tirpitz C, Reinshgen M, Adler G, König HH: Cost mesurement sed on cost diry in ptients with inflmmtory owel disese. Z Gstroenterol 2002, 40: Roick C, Kilin R, Mtschinger H, Bernert S, Mory C, Angermeyer MC: Germn dpttion of the client sociodemogrphic nd service receipt inventory - n instrument for the cost of mentl helth cre. Psychitr Prx 2001, 28(Suppl 2):S84 S AOK Bundesvernd: Krnkenhusezogene Zusmmenstellung der vereinrten Bsisfllwerte, Stnd 10. Septemer Berlin: AOK Bundesvernd; Medizincontrolling/DRG Reserch Group UM: DRG-Wegrouper. University of Münster: (Access Severl Times During 2009). 26. Kruth C, Hessel F, Hnsmeier T, Wsem J, Seitz R, Schweikert B: Empiricl stndrd for helth economic evlution in Germny - proposl y the working group methods in helth economic evlution. Gesundheitswesen 2005, 67: Vernd deutscher Rentenversicherungsträger VDR: Sttistik der Deutschen Rentenversicherung, Rehilittion Bnd 169. Würzurg: Vernd Deutscher Rentenversicherungsträger; Vernd der Angestelltenkrnkenkssen e.v: VDAK: Vergütungslisten für mulnte Leistungen, Anlge zum Vertrg üer die Erringung mulnter Leistungen. InVernd Deutscher Angestelltenkrnkenkssen E.V. (Access My 11, 2009). 29. Rote Liste 2007 Arzneimittelverzeichnis für Deutschlnd: Rote Liste Service GmH. Frnkfurt m Min: ECV Editic Cntor Verlg; Einkommensteuergesetzuch (EStG): Bundesgesetzltt Teil 1. Berlin: Bundesministerium der Justiz; Bundesmt S: Verdienste und Areitskosten Wiesden: Sttistisches Bundesmt; Bundesmt S: Areitskostenerheungen - Areitskosten im Produzierenden Gewere und im Dienstleistungsereich, Ergenisse für Deutschlnd Wiesden: Sttistisches Bundesmt; Bundesmt S: Sttistisches Jhruch 2008 für die Bundesrepulik Deutschlnd. Wiesden: Sttistisches Bundesmt; Bundesmt S: Verdienste und Areitskosten, Indizes der Areitnehmerverdienste Wiesden: Sttistisches Bundesmt; Efron B, Tishirni R: Bootstrp Methods for Stndrd Errors, Confidence Intervls, nd Other Mesures of Sttisticl Accurcy. Stt Sci 1986, 1: Hrter M, Woll S, Reuter K, Wunsch A, Bengel J: Recognition of psychitric disorders in musculoskeletl nd crdiovsculr rehilittion ptients. Arch Phys Med Rehil 2004, 85: Tiemens BG, Ormel J, Simon GE: Occurrence, recognition, nd outcome of psychologicl disorders in primry cre. Am J Psychitry 1996, 153: Koopmnschp MA, vn Exel JN, vn den Berg B, Brouwer WB: An overview of methods nd pplictions to vlue informl cre in economic evlutions of helthcre. PhrmcoEconomics 2008, 26: Zieger M, Lupp M, Mtschinger H, Meisel HJ, Günther L, Meixenserger J, Toussint R, Angermeyer MC, König HH, Riedel-Heller SG: Affective, nxiety, nd sustnce-relted disorders in ptients undergoing hernited disc surgery. Soc Psychitry Psychitr Epidemiol 2010, doi: /s doi: / Cite this rticle s: Konnopk et l.: Psychitric comoridity s predictor of in ck pin ptients undergoing disc surgery: longitudinl oservtionl study. BMC Musculoskeletl Disorders :165. Sumit your next mnuscript to BioMed Centrl nd tke full dvntge of: Convenient online sumission Thorough peer review No spce constrints or color figure chrges Immedite puliction on cceptnce Inclusion in PuMed, CAS, Scopus nd Google Scholr Reserch which is freely ville for redistriution Sumit your mnuscript t