a Department of Public Health and Primary Care, Institute of Public Health, Cambridge, UK.
b INSERM Unité 360, Paris, France.
c Psychiatric Services for the Elderly, Addenbrooke's NHS Trust, Cambridge, UK.
d MRC Biostatistics Unit, Institute of Public Health, Cambridge, UK.
e Department of Psychiatry, University of Cambridge, Cambridge, UK.
Reprint requests to: Dr Carol Brayne, Department of Public Health and Primary Care, Institute of Public Health, Forvie Site, Robinson Way, Cambridge CB2 2SR, UK. E-mail: carol.brayne{at}medschl.cam.ac.uk
![]() |
Abstract |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Methods A driving questionnaire was administered to surviving members of a cohort comprising a representative sample of individuals aged 84, the Cambridge City over 75 Cohort. Out of 546 survivors 404 completed the driving questionnaire at the 9-year follow-up. In addition, subjects were assessed, at baseline and at each follow-up, for cognitive performance using the Mini-Mental State Examination (MMSE) and for physical impairment using the Instrumental of Activities in Daily Living (IADL) scale.
Results Of the sample, 37% had driven in the past, and 8.4% were still driving, the majority regularly. The drivers tended to be younger (mean age 86.6 years), men (71%) and to be married (67.7%). Although physical disability and cognitive impairment are common in this age group, current drivers had few physical limitations on their daily activities and were not impaired on MMSE. None of the current drivers had visual impairment and 22.6% had hearing loss. Of those who had given up driving, 48.5% had given up at the age of 80. The commonest reasons for giving up driving were health problems (28.6%), and loss of confidence (17.9%). One-third reported giving up driving on advice.
Conclusion A process of self-selection takes place among older drivers. People over the age of 84 who are still driving have generally high levels of physical fitness and mental functioning, although some have some sensory loss. Given the likely increase in the number of older drivers over the next decades, safety will be improved most by strategies aimed at the entire driving population with older drivers in mind, rather than relying on costly screening programmes to identify the relatively small numbers of impaired older people who continue to drive.
Keywords Driving, elderly, cognitive function, physical impairment
Accepted 11 January 2000
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Population-based studies are rare and most studies have incorporated a relatively wide age range, yet it is likely to be in the very oldest age groups (80 years) that there will be a significant increase in the number of drivers or accidents.
This study examines the health and cognitive characteristics of very elderly people who are still driving, examines the reasons why individuals in this age group have given up driving and raises the question whether we require changes in policy in relation to older drivers.
![]() |
Subjects and Methods |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Medical conditions reported to the respondents by their doctors were recorded, in particular, angina and ischaemic heart disease, stroke and transient ischaemic attacks. These are conditions about which there are driving policies from the UK Driving Licensing Authority, and these conditions have been found to predict driving status.13 Level of physical impairment was assessed with the Instrumental Activities of Daily Living (IADL) scale developed by Lawton.14 For this analysis we have categorized total IADL score into four classes : 0, 1, 2, 3 impairment(s). Depressive symptoms were evaluated using ten questions extracted from the CAMDEX diagnostic interview.15 A depressive symptoms score was calculated for each subject by summing the responses to the 10 questions; the total score ranged from 0 to 11.16 Psychotropic drug use was obtained from the questionnaire on medications intake and includes the following classes of drugs: benzodiazepines, other minor tranquillizers, barbiturates, major tranquillizers and antidepressants. Cognition was assessed using the Mini-Mental State Examination (MMSE), which covers a range of cognitive functions and has been widely used in the UK as well as worldwide.17
Subjects were tested for near vision using the Snellen vision chart (wearing glasses if usually worn). Vision was classified as follows: no impairment when able to read font size 12, mild impairment when able to read only font size
14, severe impairment when able to read only font size
18. Distant vision was not tested.
The Whisper Test was used to assess hearing impairment. A subject was classified as impaired when failing on one of the hearing subtests (not being able to hear one of a sequence of three letters or numbers spoken when standing behind the respondent, with hearing aid if appropriate).
Statistical analysis
Analysis of variance and linear regression models were used to assess the relationship between driving status and continuous variables. Chi-square test was used to study the relationship between driving status and qualitative variables. Logistic regression models were used to examine variables associated with driving cessation. Analyses were done using the SAS® statistical package (version 6.12).18
![]() |
Results |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
|
Driving and physical impairments
Out of the 31 current drivers, none had near visual impairment and 7 had hearing impairment. Of the 31 drivers, 5 reported angina, 3 heart attack, 2 transient ischaemic attack and none stroke.
Driving and cognition
All of the current drivers completed the MMSE at the 9-year follow-up, and none scored below conventional cutpoints for severe cognitive impairment (17/18) whereas 17.8% of the non-driving population did. The mean MMSE of the current drivers was 27.2 (95% CI : 26.328.1). This was significantly different from the non-drivers whose mean score was 22.3 (95% CI : 21.923.2). Cognitive decline between baseline and 9-year follow-up was significantly less in current drivers (mean MMSE difference = 1.0, SD = 2.5) than in never drivers (mean MMSE difference = 3.6, SD = 5.0) or former drivers (mean MMSE difference = 3.2, SD = 5.5) (P < 0.001).
Reasons for giving up
Of the 108 individuals who reported ceasing to drive, 28.6% reported giving up because of health and 17.9% due to loss of confidence or other psychological reasons. Only one reported ceasing because of being told to by a doctor, four by relatives, five by other drivers and ten stated they found public transport to be more convenient. Forty-seven gave other reasons, largely financial, for stopping driving. Many reported a combination of these factors which were not seen as mutually exclusive. Table 2 presents factors associated with driving cessation. It shows that driving cessation is mainly related to severe physical impairment and cognitive impairment.
|
![]() |
Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
This study is hampered by the small number of drivers. However, the sample derives from a population base, rather than being selected on the basis of admission to hospital or having an accident. The non-drivers in the sample were more characteristic of the drop-outs than the drivers and, although it is possible that there were drivers in the drop-outs, it would have to be assumed that there was a difference between non-responding drivers and responding drivers. There was a high response amongst the survivors (404/546) and some of the non-response was definitely due to frailty. As far as we are aware from death certificates, no death has been due to road traffic accidents in this group.
Although MMSE can be viewed as a relatively crude instrument for measuring cognitive functions, higher levels of performances, as demonstrated by the drivers, are rarely associated with late onset of dementia. Moreover, MMSE has been found to correlate well (r = 0.71, P < 0.01) with in-traffic tests scores allocated by active observations of driving in licensed drivers.19
The study is UK based and of a particular age cohort, predominantly women. There are likely to be considerable cultural, including differential gender, effect and cohort effects which will necessitate monitoring the ways in which older populations' attitudes to driving evolve.
The proportion of drivers in this population was less than the 19% reported from a study of acute geriatric wards, but this hospital-based study included younger respondents.20 A case-control study has suggested that there was no significant difference between cases with Alzheimer's disease and controls in their accident record, probably due to the reduction in driving in the cases.20 The case-control approach led to similar findings to oursin the cases who had ceased driving, neuropsychological test scores were also consistently lower.
This UK-based study found only one individual who had been advised to stop driving by a physician; this is in marked contrast to two US studies in which between 27% and 23% were so advised.20,21 In Persson's study of ex-drivers, the proportions who reported loss of confidence and medical conditions reported these similarly as factors in their decision, but more reported advice from others.20 The main reason reported for driving cessation in another UK-based study was cost, also cited by many in our study.1
In Morgan's study, 22 out of 43 of the drivers on acute geriatric wards suffered from significant conditions which could interfere with driving.1 These were angina, transient ischaemic attacks, blackouts, poor vision and hypoglycaemia. These conditions were rare in our population sample. This difference almost certainly results from the nature of the hospital sample. It would have been of interest in the hospital sample to ascertain whether these individuals continued to drive once discharged from that episode, as these health reasons are also those which are associated with driving cessation.1
This study shows clearly that older people themselves can make the decision to stop driving, and that there are factors which influence this decision. More worryingly, however, this study suggests that the call to screen for dementia or health status in the older population will not reduce the marked rise in accidents seen with age, because those with cognitive impairment and failing health in the oldest age groups have already chosen to stop driving. Thus the bulk of accidents seen in the older age groups is likely to be the result of accidents involving fit older people, with relatively intact health and cognition. This is a finding of some public health importance and suggests that a wider-reaching strategy should be pursued to identify what prevents accidents in older age groups. Relying on costly and necessarily regular screening procedures to identify particularly high-risk individuals is unlikely to yield the greatest reduction in accidents. There will be considerable room for errorone study of selected older drivers investigated, with a computerized battery of tests, a range of cognitive functions but could identify only 80% of those who had had unsafe incidents and misclassified 20%.22,23 More research is needed to establish the processes responsible for increased accidents among older drivers. In addition, many factors related to the design of car and road safety must take the ageing population into account, otherwise the proportion of accidents due to aged drivers will increase, despite efforts to identify risky drivers. Such design features would also reduce accidents in younger age groups.
![]() |
Acknowledgments |
---|
![]() |
References |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
2 Morgan R, King D. The older drivera review. Postgrad Med J 1995; 71:52528.[Abstract]
3 O'Neill D. Physicians, elderly drivers and dementia. Lancet 1992; 339:4143.[ISI][Medline]
4 Marotolli RA, Mendes de Leon CF, Glass TA et al. Driving cessation and increased depressive symptoms: prospective evidence from the New Haven EPESE. J Am Geriatr Soc 1997;45:20206.[ISI][Medline]
5 Reuben DB. Dementia and driving. J Am Geriatr Soc 1991;39:113738.[ISI][Medline]
6 Drachman DA, Swearer JM. Driving and Alzheimer's disease: the risk of crashes. Neurology 1993;43:244856.[Abstract]
7 O'Neill D. Dementia and driving: screening, assessment and advice. Lancet 1996;348:1114.[ISI][Medline]
8 Carr D, Jackson TW, Madden DJ, Cohen HJ. The effect of age on driving skills. J Am Geriatr Soc 1992;40:56773.[ISI][Medline]
9 Perryman KM, Fitten LJ. Effects of normal aging on the performance of motor-vehicle operational skills. J Geriatr Psychiatry Neurol 1996;9:13641.[ISI][Medline]
10 Cerreli E. Older Drivers, the Age Factor in Traffic Safety. Department of Transport HS 807402 NHTSA Tech. Rep. Feb. 1989.
11 Rabbitt P, Carmichael A, Jones S, Holland C. When and Why Older Drivers Give Up Driving. AA Foundation for Road Safety Research, 1996.
12 O'Connor DW, Pollitt PA, Hyde JB, Fellows JL, Miller ND, Roth M. The prevalence of dementia as measured by the Cambridge Mental Disorders of the Elderly Examination. Acta Psychiatr Scand 1989;79:19098.[ISI][Medline]
13 Kington R, Reuben D, Rogowski J, Lillard L. Sociodemographic and health factors in driving patterns after 50 years of age. Am J Public Health 1994;84:132729.[Abstract]
14 Lawton MP, Brody EM. Assessment of older people: self-maintaining and instrumental activities of daily living. Gerontologist 1969;9: 17986.[ISI][Medline]
15 Roth M, Tym E, Mountjoy CQ et al. The CAMDEX. A standardised instrument for the diagnosis of mental disorder in the elderly with special reference to the early detection of dementia. Br J Psychiatry 1986;149:698709.[Abstract]
16 Girling DM, Huppert FA, Brayne C, Paykel ES, Gill C, Mathewson D. Depressive symptoms in the very elderly-their prevalence and significance. Int J Geriat Psychiatry 1995;10:497504.[ISI]
17 Folstein MF, Folstein SE, McHugh PR. Mini-Mental State: a practical method for grading the cognitive state of patients for the clinician. J Psychiatry Res 1975;12:189-98.[ISI][Medline]
18 SAS User's Guide. Version 6. Cary, NC: SAS Institute, 1991.
19 Odenheimer GL, Beaudet M, Jette AM, Albert MS, Grande L, Minaker KL. Performance-based driving evaluation of the elderly driver: safety, reliability, and validity. J Gerontol 1994;49:M15359.[ISI][Medline]
20 Trobe JD, Waller PF, Cook-Flannagan CA, Teshima SM, Bieliaukas LA. Crashes and violations among drivers with Alzheimer's disease. Arch Neurol 1996;53:41116.[Abstract]
21 Persson D. The elderly driver: deciding when to stop. Gerontologist 1993;33:8891.[Abstract]
22 McKnight AJ, McKnight AS. Multivariate analysis of age-related driver ability and performance deficits. Accid Anal Prev 1999;31:44554.[ISI][Medline]
23 Dobbs AR. Evaluating the driving competence of dementia patients. Alzheimer Dis Assoc Disord 1997;11:812.[ISI][Medline]