Advertisement
Research Article

Incident Hip Fractures among Community Dwelling Persons with Alzheimer’s Disease in a Finnish Nationwide Register-Based Cohort

  • Anna-Maija Tolppanen mail,

    anna-maija.tolppanen@uef.fi

    Affiliation: Institute of Clinical Medicine – Neurology, University of Eastern Finland, Kuopio, Finland

    X
  • Piia Lavikainen,

    Affiliation: Kuopio Research Centre of Geriatric Care, University of Eastern Finland, Kuopio, Finland

    X
  • Hilkka Soininen,

    Affiliations: Institute of Clinical Medicine – Neurology, University of Eastern Finland, Kuopio, Finland, Department of Neurology, Kuopio University Hospital, Kuopio, Finland

    X
  • Sirpa Hartikainen

    Affiliations: Kuopio Research Centre of Geriatric Care, University of Eastern Finland, Kuopio, Finland, Pharmacology and Geriatric Pharmacotherapy Unit, University of Eastern Finland, Kuopio, Finland

    X
  • Published: March 18, 2013
  • DOI: 10.1371/journal.pone.0059124

Abstract

Background

Previous cohort studies have shown that persons with Alzheimer’s disease (AD) have a higher risk of hip fractures but recent data from large representative cohorts is scarce.

Methods

We investigated the association between AD and prevalent and incident hip fractures in an exposure-matched cohort study conducted in Finland 2002–2009 (the Medication and Alzheimer’s disease in 2005 study; MEDALZ-2005). The study population included all community-dwelling persons with verified AD diagnosis in Finland on December 31, 2005 and one matched comparison person per AD case (N = 56,186, mean age 79.9 (SD 6.8) years, range 42–101 years). The diagnosis of AD was extracted from a special reimbursement register. Data on hip fractures during 2002–2009 was extracted from the Finnish National hospital discharge register. Analyses of incident hip fractures (n = 2,861) were restricted to years 2006–2009.

Results

Persons with AD were twice as likely to have previous hip fracture in 2005 (odds ratio, 95% confidence interval 2.00, 1.82–2.20) than matched aged population without AD. They were also more likely to experience incident hip fracture during the four-year follow-up (hazard ratio, 95% confidence interval 2.57, 2.32–2.84, adjusted for health status, psychotropic drug and bisphosphonate use). The AD-associated risk increase decreased linearly across age groups. Although people with AD had higher risk of hip fractures regardless of sex, the risk increase was larger in men than women.

Conclusion

Findings from our nationwide study are in line with previous studies showing that persons with AD, regardless of sex or age, have higher risk of hip fracture in comparison to general population. Although there was some suggestion of effect modification by age or sex, AD was consistently associated with doubling of the risk of incident hip fracture.

Introduction

Alzheimer’s disease (AD) is the most common form of dementia. Although the neuropsychiatric symptoms themselves affect the quality of life, individuals with AD are at increased risk for other comorbidities which further decrease the individuals’ well-being and increase the healthcare costs. Persons with cognitive impairment [1], [2] and dementia, including AD [3] have higher risk of falls. Individual cohort studies, [1], [4][12] analyses based on US Medicare claims data [13], [14], UK electronic database of primary care data [15] and a recent meta-analysis [16] have shown that individuals with AD have 2–3 fold risk of hip fracture in comparison to dementia-free individuals. Importantly, persons with AD also have worse prognosis after hip fracture [17]: they are more likely to be immobilized [18] and have higher post-fracture mortality [15].

Majority of the previous studies have been conducted in restricted cohorts [1], [4][12] and one of the three larger studies [13][15] is based on data from the mid-1990s [13]. Thus, recent data from a large representative cohort is scarce. Higher incidence of hip fractures, especially in combination with worse outcomes following the hip fractures would emphasize the need for effective hip fracture prevention strategies. We investigated the prevalence and incidence of hip fractures among people with AD in a register-based nationwide cohort including all non-institutionalized persons with AD residing in Finland in 2005.

Participants and Methods

Study Cohort

Retrospective (years 2002–2005) and prospective (years 2006–2009) data for the Medication and Alzheimer’s Disease (MEDALZ-2005) study were used. The MEDALZ-2005 cohort includes all community-dwelling persons with a verified diagnosis of Alzheimer’s disease residing in Finland on 31 December 2005 (n = 28,093) and a single age-, sex- and region of residence- matched comparison person for each individual with AD (N = 56,186). Altogether 2,015 comparison persons converted to AD during the four-year follow-up on 2006–2009. The age range of the cohort was 42–101 years (mean 79.9 (SD 6.8) years) and 38,086 (67.8%) of the sample were women. AD diagnosis was based on the NINCS-ADRDA and DSM-IV criteria for Alzheimer’s disease.{[19], [20] Persons with AD were identified from the Special Reimbursement Register maintained by the Social Insurance Institution of Finland (SII). The Special Reimbursement Register contains records of persons who are eligible to receive reimbursement due to e.g. AD, cancer or diabetes. The comparison persons were identified from the register that contains all residents of Finland who are entitled to benefits by the Social Insurance Institution (SII). Each resident of Finland is assigned a unique social security number which was used to track participant data and link data from different national registers of hospital discharges, prescriptions and mortality. Linking was performed by SII and all data were de-identified before submission to the research team. No ethics committee approval was required as only de-identified data were used and the study participants were not contacted. Formation of the study sample is described in Figure 1.

thumbnail

Figure 1. Formation of study cohort.

doi:10.1371/journal.pone.0059124.g001

Outcomes

Hip fractures during 2002–2009 were identified from the national hospital discharge register based on the following ICD-10 codes: S72.0 (fracture of neck of femur), S72.1 (pertrochanteric fracture) and S72.2 (subtrochanteric fracture). Finnish hospital discharge register is a statutory register containing information on use of in- and outpatient healthcare services. The individual-level data is collected and updated continuously.

Confounders

Information on cardiovascular diseases, cancer, diabetes (type 1 or 2), pernicious anemia and other disturbances in absorption of vitamin B12, Parkinson’s disease, epilepsy, glaucoma and rheumatoid conditions was obtained from Finnish National Prescription Register. Details are given in Supplementary Table 1 (see file Table S1). To account for medications which may affect the susceptibility to hip fractures, we adjusted for use of psychotropic drugs (The Anatomical Therapeutic Chemical: ATC Classification system classes N05, N06A and N06B) and bisphosphonates (ATC classes M05BA and M05BB). Psychotropic and bisphosphonate use were defined as at least one filled prescription during 2005. Data on filled prescriptions were obtained from the National Prescription register, which contains records of prescription drugs purchased by all Finnish residents living in non-institutionalized settings.

thumbnail

Table 1. Association of Alzheimer’s disease with hip fractures.

doi:10.1371/journal.pone.0059124.t001

Statistical Analyses

All statistical analyses were conducted with Stata 12.0 (Stata Corp LP, College Station, TX USA). Association between prevalent hip fractures before AD diagnosis was assessed with conditional logistic regression. Figure 1 shows how the study population for incident hip fractures after AD diagnosis was derived. Due to the cohort definition, January 1st 2006 was set as a beginning of follow-up and participants who had experienced hip fracture before beginning of follow up or AD diagnosis were excluded from the incidence analyses (n = 2,027). In addition 145 comparison persons had temporarily been entitled to reimbursed AD medication before 2005 and were excluded. Because our study is an exposure-matched cohort (with AD as an exposure), we excluded those persons whose referent was excluded, leaving 25,986 AD-comparison person pairs. Altogether 1,803 comparison persons converted to AD during the follow-up and thus AD was modeled as a time-dependent covariate.

Proportional hazards for incident hip fractures were estimated with Cox regression. Matching was taken into account in the analysis. We present hazard rations for the whole study population and due to interaction (P for interaction with sex = 0.05 and P for interaction with age<0.001), sex- and age group-wise hazard ratios are also presented. Chronological age was categorized as <80, 80–84 and ≥85 years. We also present the results according to quartiles of approximate age at Alzheimer’s disease diagnosis, calculated from the diagnosis of AD or first reimbursed purchase of AD medication, depending on which one occurred first. The cutoffs for classes of age at AD diagnosis were 74, 79 and 83 years, resulting to the following categories: 38.9–73.9, 74–78.9, 79.0–82.9 and 83.0–99.0 years.

Differences in the mean age of first fracture between persons with and without AD were estimated with t-test. The age at first fracture was normally distributed.

Results

The prevalence of previous hip fractures in the full study cohort (N = 56,186) in December 2005 was 4.7% (n = 1,312) in persons with AD and 2.4% (n = 667) in those without AD. These individuals, together with 48 comparison persons who experienced a hip fracture before they converted to AD during the follow-up were excluded from the analysis of incident hip fractures. Persons with AD were more likely to have previous hip fractures (OR, 95% CI 2.00, 1.82–2.20) and they had experienced the fractures at younger age than those without Alzheimer’s disease (difference for the age at hip fracture 1.25 years, 95% CI 0.72–1.79 years). The mean age at fracture was 81.6 (SD 5.8) years for cases and 82.8 (SD 5.6) years for controls (P for difference <0.0001).

Altogether 2,861 persons (2,016 with AD and 845 with no AD) experienced an incident hip fracture during 2006–2009. The follow-up time was 87,888 person-years in the AD group and 83,324 years in the non-AD group.

Table 1 shows the association between AD and incident hip fractures. In the crude analyses, persons with Alzheimer’s disease were 2.7 times more likely to experience incident hip fractures during 2006–2009 than persons without AD (Model 1). Adjustment for comorbidities resulted in a modest strengthening in the association in the whole population and two youngest age groups while an opposite trend was observed in the oldest age group (Model 2). Further adjustment for the use of psychotropic drugs or bisphosphonates attenuated the association in all age groups (Model 3) but in the whole study population, the relative risk of hip fracture in the AD group was still 2.6 times higher in comparison to persons without AD. The magnitude of the association was stronger in the youngest age group, although AD was consistently associated with higher risk of incident hip fractures in all age groups.

Table 2 shows the association between AD and incident hip fractures in men and women. Although people with AD had higher risk of hip fractures regardless of sex, the risk increase was slightly larger in men than women when all age groups were pooled in the analyses. In the youngest age group (<80 years, the risk increase was larger in women than men while an opposite pattern was observed in the two oldest age groups (age 80–84 years and age ≥86 years).

thumbnail

Table 2. Association of Alzheimer’s disease with hip fractures in men and women.

doi:10.1371/journal.pone.0059124.t002

Association between AD and hip fracture according to AD duration are shown in Table 3. In comparison to those with no AD, risk of hip fractures was highest among those who were youngest when AD was diagnosed (38.9–73.9 years) and the relative risk difference decreased across categories of age at AD diagnosis. These findings were in line with the pattern observed with chronological age (Table 1).

thumbnail

Table 3. Hazard ratios for hip fractures according to age at AD diagnosis.

doi:10.1371/journal.pone.0059124.t003

Discussion

In this nationwide study individuals with AD had two times higher prevalence of previous hip fractures and when these individuals were excluded from the analyses, the incidence of new hip fractures was 2.6-fold in those with AD in comparison to their matched controls. These estimates are in accordance with previous studies showing a 2-3-fold increase in hip fracture risk among AD patients [1], [4], [6][8], [10][15], [21].

Strengths of our study include large, representative cohort: all AD cases entitled to special reimbursement of AD medication and residing in Finland were included. Thus our study population includes only cases that were verified by medical examination including computed tomography/magnetic resonance imaging scan, exclusion of alternative diagnoses and confirmation of the AD diagnosis by a neurologist or geriatrician. The Finnish Current Care Guidelines recommend that all persons with AD are treated with anti-dementia drugs unless there is a specific contraindication. Patients with mild or moderate AD are entitled to reimbursed anti-dementia medication, but the reimbursement is not withdrawn if/when the patient develops severe AD. Thus our study sample included persons with all stages of AD. The Finnish Hospital Discharge Register covers nearly all occurring hip fractures. A study comparing audit and register-based data showed that 98.1% of occurred hip fractures were recorded in the hospital discharge register [22]. Register-based diagnoses of dementia/AD likely underestimate the disease incidence and thus we cannot exclude the possibility that some of the persons who did not have special reimbursement for AD medication actually had AD. Thus, our results may be an underestimate of the true association although the comparison to previous studies suggests that this bias in likely to be small.

Due to the register-based approach, we were unable to adjust for lifestyle-based confounders or genetic risk factors, such as apolipoprotein E ε4-allele, which has been suggested to be a risk factor for hip fracture, independent of the effect of dementia and falling [23], [24]. However, we extracted information on co-morbidities, such as cancer, diabetes and cardiovascular diseases, which likely capture some variation in lifestyle. We acknowledge that some residual confounding is likely, although the results were in line with previous studies that were able to adjust for directly measured lifestyle factors [1], [4][12]. We were also able to adjust for the use of psychotropic and bisphosphonate medication on the basis of prescription data. In addition, the hospital discharge data were available from years 2002–2009 which may have affected our ability to strictly exclude all previous hip fractures. Our study was restricted to individuals who were non-institutionalized at the baseline, which may affect the generalisability of the results.

Although less than 10% of falls cause hip fracture, [25], [26] over 90% of hip fractures are due to falls [27], [28] and accordingly, a higher number of falls further increases the risk of hip fracture [29]. Accidental injuries, including falls are the most common adverse event among institutionalized AD patients [30]. Both cognitive impairment [1], [2] and different dementias, including AD [3] are associated with increased risk of falls. Consequently, in a prospective study of female patients with AD, those with falls were more likely to experience hip fractures [31]. The association between dementia and falls is not restricted to those living in institutionalized settings [3] and the increased risk of falling can be explained by gait and balance disorders, defective neuromuscular regulation, visual disorders, postural hypotension, depression, low body mass index or use of psychotropic drugs, all of which are more common among individuals with AD [32]. Surprisingly, findings from an older cohort suggest that too fast gait may increase the risk of falling: although frail patients with dementia walked slowly, they still walked relatively too fast considering the overall degree of physical impairment that should have warranted a slower gait [33]. Motor function is also affected and especially dual-tasking (i.e. performing a cognitive task while walking) is impaired already in the mild forms of AD [34].

Due to the definition of AD in our study (i.e. clinically verified diagnosis of AD), the increase in hip fractures could be due to adverse effects of drugs instead of risk mediated by the disease process. Use of acetylcholinesterase inhibitors is associated with higher rates of syncope, bradycardia, and hip fractures in older adults with dementia, [35] although a recent case-control study of 2258 AD patients (and 80 hip fractures) found an association between acetylcholinesterase inhibitor use and decreased risk of hip fracture [36]. In our study cohort, 86% of persons with AD used anti-dementia drugs and 71% of these used acetylcholinesterase inhibitors in 2005 [37]. However, the prevalence of hip fractures was higher among AD cases, suggesting that the increase could mainly be due to factors associated with the ongoing Alzheimer’s disease process, such as postural hypotension, perception difficulties or motor problems.

In conclusion, findings from this nationwide study are in line with previous studies showing that persons with AD, regardless of age, sex or disease duration have higher risk of hip fracture in comparison to the general population. As people with AD are known to have worse prognosis after hip fracture, these findings highlight the need for effective strategies to prevent hip fractures in this vulnerable population.

Supporting Information

Table S1.

Special reimbursement codes used for extracting information on confounders.

doi:10.1371/journal.pone.0059124.s001

(DOCX)

Author Contributions

Conceived and designed the experiments: AMT PL SH. Analyzed the data: AMT. Wrote the paper: AMT PL HS SH.

References

  1. 1. Buchner DM, Larson EB (1987) Falls and fractures in patients with Alzheimer-type dementia. JAMA : The Journal of the American Medical Association 257: 1492–1495. doi: 10.1001/jama.257.11.1492
  2. 2. Graafmans WC, Ooms ME, Hofstee HM, Bezemer PD, Bouter LM, et al. (1996) Falls in the elderly: A prospective study of risk factors and risk profiles. American Journal of Epidemiology 143: 1129–1136. doi: 10.1093/oxfordjournals.aje.a008690
  3. 3. Allan LM, Ballard CG, Rowan EN, Kenny RA (2009) Incidence and prediction of falls in dementia: A prospective study in older people. PloS One 4: e5521. doi: 10.1371/journal.pone.0005521
  4. 4. Saxena P, Shankar J (2000) Contralateral hip fractures - can predisposing factors be determined? Injury 31: 421–424. doi: 10.1016/s0020-1383(00)00012-7
  5. 5. Rapp K (2011) People with Alzheimer’s disease are at increased risk of hip fracture and of mortality after hip fracture. Evidence-Based Nursing 14: 78–79. doi: 10.1136/ebn1160
  6. 6. Weller I, Schatzker J (2004) Hip fractures and Alzheimer’s disease in elderly institutionalized Canadians. Annals of Epidemiology 14: 319–324. doi: 10.1016/j.annepidem.2003.08.005
  7. 7. Weller II (2000) The relation between hip fracture and Alzheimer’s disease in the canadian national population health survey health institutions data, 1994–1995. A cross-sectional study. Annals of Epidemiology 10: 461. doi: 10.1016/s1047-2797(00)00085-5
  8. 8. Harboun M, Dorenlot P, Cohen N, Steinhagen-Thiessen E, Ankri J (2008) Impact of hip fracture, heart failure and weight loss on the risk of institutionalization of community-dwelling patients with dementia. International Journal of Geriatric Psychiatry 23: 1245–1252. doi: 10.1002/gps.2058
  9. 9. Formiga F, Navarro M, Duaso E, Chivite D, Ruiz D, et al. (2008) Factors associated with hip fracture-related falls among patients with a history of recurrent falling. Bone 43: 941–944. doi: 10.1016/j.bone.2008.06.014
  10. 10. Trimpou P, Landin-Wilhelmsen K, Oden A, Rosengren A, Wilhelmsen L (2010) Male risk factors for hip fracture-a 30-year follow-up study in 7,495 men. Osteoporosis International : A Journal Established as Result of Cooperation between the European Foundation for Osteoporosis and the National Osteoporosis Foundation of the USA 21: 409–416. doi: 10.1007/s00198-009-0961-7
  11. 11. Melton LJ,3rd, Beard CM, Kokmen E, Atkinson EJ, O’Fallon WM (1994) Fracture risk in patients with Alzheimer’s disease. Journal of the American Geriatrics Society 42: 614–619.
  12. 12. Mitani S, Shimizu M, Abo M, Hagino H, Kurozawa Y (2010) Risk factors for second hip fractures among elderly patients. Journal of Orthopaedic Science : Official Journal of the Japanese Orthopaedic Association 15: 192–197. doi: 10.1007/s00776-009-1440-x
  13. 13. Sloan FA, Taylor DH Jr (2002) Effect of Alzheimer disease on the cost of treating other diseases. Alzheimer Disease and Associated Disorders 16: 137–143. doi: 10.1097/00002093-200207000-00002
  14. 14. Zhao Y, Kuo TC, Weir S, Kramer MS, Ash AS (2008) Healthcare costs and utilization for medicare beneficiaries with Alzheimer’s. BMC Health Services Research 8: 108. doi: 10.1186/1472-6963-8-108
  15. 15. Baker NL, Cook MN, Arrighi HM, Bullock R (2011) Hip fracture risk and subsequent mortality among Alzheimer’s disease patients in the united kingdom, 1988–2007. Age and Ageing 40: 49–54. doi: 10.1093/ageing/afq146
  16. 16. Zhao Y, Shen L, Ji HF (2012) Alzheimer’s disease and risk of hip fracture: A meta-analysis study. TheScientificWorldJournal 2012: 872173. doi: 10.1100/2012/872173
  17. 17. Holmes J, House A (2000) Psychiatric illness predicts poor outcome after surgery for hip fracture: A prospective cohort study. Psychological Medicine 30: 921–929. doi: 10.1017/s0033291799002548
  18. 18. Tanaka S, Yoshimura N, Kuroda T, Hosoi T, Saito M, et al. (2010) The fracture and immobilization score (FRISC) for risk assessment of osteoporotic fracture and immobilization in postmenopausal women–A joint analysis of the Nagano, Miyama, and Taiji cohorts. Bone 47: 1064–1070. doi: 10.1016/j.bone.2010.08.019
  19. 19. McKhann G, Drachman D, Folstein M, Katzman R, Price D, et al. (1984) Clinical diagnosis of alzheimer’s disease: Report of the NINCDS-ADRDA work group under the auspices of department of health and human services task force on Alzheimer’s disease. Neurology 34: 939–944. doi: 10.1212/wnl.34.7.939
  20. 20. American Psychiatric Association (1994) Diagnostic and statistical manual of mental disorders. Washington DC: American Psychiatric Association.
  21. 21. Formiga F, Lopez-Soto A, Duaso E, Ruiz D, Chivite D, et al. (2008) Characteristics of fall-related hip fractures in community-dwelling elderly patients according to cognitive status. Aging Clinical and Experimental Research 20: 434–438. doi: 10.1007/bf03325149
  22. 22. Sund R, Juntunen M, Luthje P, Huusko T, Hakkinen U (2011) Monitoring the performance of hip fracture treatment in Finland. Annals of Medicine 43 Suppl 1: S39–46. doi: 10.3109/07853890.2011.586360
  23. 23. Johnston JM, Cauley JA, Ganguli M (1999) APOE 4 and hip fracture risk in a community-based study of older adults. Journal of the American Geriatrics Society 47: 1342–1345.
  24. 24. Cauley JA, Zmuda JM, Yaffe K, Kuller LH, Ferrell RE, et al. (1999) Apolipoprotein E polymorphism: A new genetic marker of hip fracture risk–the study of osteoporotic fractures. Journal of Bone and Mineral Research : The Official Journal of the American Society for Bone and Mineral Research 14: 1175–1181. doi: 10.1359/jbmr.1999.14.7.1175
  25. 25. Tinetti ME, Speechley M, Ginter SF (1988) Risk factors for falls among elderly persons living in the community. N Engl J Med 319: 1701–1707. doi: 10.1056/nejm198812293192604
  26. 26. Cummings SR, Nevitt MC (1994) Non-skeletal determinants of fractures: The potential importance of the mechanics of falls. Study of osteoporotic fractures research group. Osteoporosis International : A Journal Established as Result of Cooperation between the European Foundation for Osteoporosis and the National Osteoporosis Foundation of the USA 4 Suppl 1: 67–70. doi: 10.1007/bf01623439
  27. 27. Norton R, Campbell AJ, Lee-Joe T, Robinson E, Butler M (1997) Circumstances of falls resulting in hip fractures among older people. Journal of the American Geriatrics Society 45: 1108–1112.
  28. 28. Parkkari J, Kannus P, Palvanen M, Natri A, Vainio J, et al. (1999) Majority of hip fractures occur as a result of a fall and impact on the greater trochanter of the femur: A prospective controlled hip fracture study with 206 consecutive patients. Calcified Tissue International 65: 183–187. doi: 10.1007/s002239900679
  29. 29. Cumming RG, Klineberg RJ (1994) Fall frequency and characteristics and the risk of hip fractures. Journal of the American Geriatrics Society 42: 774–778.
  30. 30. Oliveria SA, Liperoti R, L’italien G, Pugner K, Safferman A, et al. (2006) Adverse events among nursing home residents with alzheimer’s disease and psychosis. Pharmacoepidemiology and Drug Safety 15: 763–774. doi: 10.1002/pds.1274
  31. 31. Sato Y, Kanoko T, Satoh K, Iwamoto J (2004) Risk factors for hip fracture among elderly patients with alzheimer’s disease. Journal of the Neurological Sciences 223: 107–112. doi: 10.1016/j.jns.2004.03.033
  32. 32. Cummings SR, Nevitt MC, Browner WS, Stone K, Fox KM, et al. (1995) Risk factors for hip fracture in white women. Study of osteoporotic fractures research group. The New England Journal of Medicine 332: 767–773. doi: 10.1056/nejm199503233321202
  33. 33. van Iersel MB, Verbeek ALM, Bloem BR, Munneke M, Esselink RAJ, et al. (2006) Frail elderly patients with dementia go too fast. Journal of Neurology, Neurosurgery & Psychiatry 77: 874–876. doi: 10.1136/jnnp.2005.084418
  34. 34. Pettersson AF, Olsson E, Wahlund LO (2005) Motor function in subjects with mild cognitive impairment and early Alzheimer’s disease. Dementia and Geriatric Cognitive Disorders 19: 299–304. doi: 10.1159/000084555
  35. 35. Gill SS, Anderson GM, Fischer HD, Bell CM, Li P, et al. (2009) Syncope and its consequences in patients with dementia receiving cholinesterase inhibitors: A population-based cohort study. Archives of Internal Medicine 169: 867–873. doi: 10.1001/archinternmed.2009.43
  36. 36. Tamimi I, Ojea T, Sanchez-Siles JM, Rojas F, Martin I, et al. (2012) Acetylcholinesterase inhibitors and the risk of hip fracture in Alzheimer’s disease patients: A case-control study. Journal of Bone and Mineral Research : The Official Journal of the American Society for Bone and Mineral Research.
  37. 37. Laitinen ML, Bell JS, Lavikainen P, Lonnroos E, Sulkava R, et al. (2011) Nationwide study of antipsychotic use among community-dwelling persons with alzheimer’s disease in Finland. International Psychogeriatrics/IPA 23: 1623–1631. doi: 10.1017/s1041610211001621