New Opioid Analgesic Use and the Risk of Injurious Single-Vehicle Crashes in Drivers Aged 50–80 Years: A Population-based Matched Case–Control Study

Joel Monárrez-Espino; Lucie Laflamme; Christian Rausch; Berty Elling; Jette Möller

Age Ageing. 2016;45(5):628-634.

Abstract and Introduction

Abstract

Background: the increasing trend in opioid analgesic use among older drivers has raised concerns about their risk of being involved in car crashes.

Aim: to investigate if older drivers who started using opioid analgesics have a higher probability of being involved in injurious crashes.

Methods: population-based matched case–control study. Data from population registers were merged using a personal identity number. Cases were drivers aged 50–80 years responsible for a single vehicle crash between 01.07.05 and 31.12.09 that led to at least one injured passenger (n = 4,445). Four controls were randomly matched to each case by sex, birth month/year, and residence area from persons holding a valid driving license who did not crash during the study period. New use was defined as at least one dispensation within 1–30 days prior to the crash, but none within the previous 31–180 days; frequent use when ≥3 dispensations were given within 0–180 days, with at least one within 31–180 days. Individuals using 1–2 non-opioid analgesic medications were used as reference category. Conditional logistic regression was used to estimate odds ratios (OR; 95% CI) adjusting for benzodiazepine use, co-morbidity, civil status and occupation.

Results: adjusted odds for new use were two-fold that of drivers using 1–2 non-opioid analgesics medications (2.0; 1.6–2.5). For frequent use, adjusted odds were also increased regardless of number of dispensations (3–4 = 1.7; 1.3–2.1, 5–6 = 1.6; 1.2–2.3, and ≥7 = 1.7; 1.3–2.1).

Conclusion: new, but also frequent opioid analgesic use, resulted in an increased probability of single vehicle crashes. While more epidemiologic evidence is needed, patients could be advised to refrain from driving when using opioid analgesics.

Introduction

In Sweden, as in many countries, there has been a shift in the age distribution of the population, with an increasing proportion of older people. At present, 19.6% of the inhabitants is aged ≥65 years, but this percentage is expected to reach 25% by 2050.^[1] Thus, an increasing number of older adults can now live an independent and active life, which in many settings involves the use of a vehicle as a means of sustained mobility.

However, lower sensory, memory, cognition, attention and other relevant functions required to drive as well as slower physical responses are common in older persons.^[2] Also, they usually suffer from chronic medical conditions that may further limit their driving abilities.^[3] Such morbidities often require medications, some of which give side effects that can affect driving performance and increase crash risks.^[3,4]

The use of opioids under driving conditions has been^[5,6] and continues to be^[7,8] a subject of debate. While it is known that opioids can affect driving performance due to symptoms arising from their direct effect on the nervous system, some consider them to be relatively safe, at least among chronic users,^[5] possibly due to tolerance of the side effects.^[7] Some studies even report that relieving pain could actually improve cognitive function^[9] and visual and auditory reflexes.^[10] However, so far most evidence on the topic is based on cognitive^[7,11] and experimental^[5,8] or simulation studies^[12] conducted in all adults, with a number of them focusing on the treatment of addiction.

The opioid analgesics, commonly used to treat pain and other conditions of older people,^[13] is a group of medications where there is limited epidemiological evidence of their effect on the risk of road traffic crashes.

A recent meta-analysis of epidemiologic studies on the role of analgesics and the risk of road traffic crashes in senior drivers^[14] revealed a significant increase in the probability of crashing (OR 1.2; 95% CI 1.08–1.32), which could be due to the presence of new opioid analgesic users who have not developed adaptation to the medication.

We aim to investigate this further using national Swedish material focusing on older adult drivers who recently started opioid analgesic treatment and assessed whether they had a higher chance of being involved in single injurious crashes compared with frequent opioid analgesic users and non-users.

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Abstract and Introduction
Methods
Results
Discussion
References
Sidebar

Table 1. Distribution of cases and controls and matched odds ratios for exposure to medications and potential factors linked to the risk of injurious single-vehicle crashes
Exposure		Frequency (%)^a		Matched OR (95% CI)^b
Exposure		Cases	Controls	Matched OR (95% CI)^b
Opioid analgesics^c	No	4,142 (93.2)	17,419 (98.0)	1.00
Opioid analgesics^c	Yes	303 (6.8)	361 (2.0)	2.37 (2.11–2.66)
Benzodiazepines^c	No	4,115 (92.6)	16,698 (96.6)	1.00
Benzodiazepines^c	Yes	330 (7.4)	581 (3.4)	1.83 (1.63–2.05)
Nervous system medications^c	No	3,686 (82.9)	16,182 (91.0)	1.00
Nervous system medications^c	Yes	759 (17.1)	1,598 (9.0)	1.73 (1.60–1.87)
Cardiovascular medications^c	No	3,728 (83.9)	15,277 (85.9)	1.00
Cardiovascular medications^c	Yes	717 (16.1)	2,503 (14.1)	1.13 (1.04–1.23)
Number of different medications dispensed^d	0	2,657 (59.8)	12,085 (68.0)	1.00
	1–2	998 (22.5)	3,667 (20.6)	1.18 (1.10–1.27)
	3–4	430 (9.7)	1,231 (6.9)	1.43 (1.29–1.59)
	≥5	360 (8.1)	797 (4.5)	1.72 (1.54–1.92)
Marital status	Married	2,356 (53.0)	11,115 (62.5)	1.00
	Never married	632 (14.2)	2,502 (14.1)	1.15 (1.05–1.25)
	Divorced	1,093 (24.6)	3,085 (17.4)	1.49 (1.39–1.60)
	Widowed	348 (7.8)	915 (5.1)	1.57 (1.40–1.76)
Occupation	Professionals	911 (20.5)	4,117 (23.2)	1.00
	Technicians	1,381 (31.1)	6,182 (34.8)	1.00 (0.92–1.09)
	Skilled workers	1,417 (31.9)	4,964 (27.9)	1.22 (1.13–1.37)
CCI score^e	0 points	4,180 (94.0)	17,380 (97.8)	1.00
CCI score^e	≥1 point	265 (6.0)	400 (2.2)	2.05 (1.81–2.32)

^aTotals might not add up to hundred percent due to missing data.
^bConditional logistic regression for cases and controls matched by sex, birth date and place of residence.
^cExposure to at least one medication dispensed within 1–30 days prior to the index date.
^dWithin 1–30 days prior to the index date, excluding opioid analgesics and benzodiazepines.
^eWeighted Charlson Comorbidity Index.

Table 2. Distribution of cases and controls with adjusted odds ratios for opioid analgesic exposure on the risk of injurious single-vehicle crashes
Exposure definitions		Frequency (%)^a		Matched OR (95% CI)^b
Exposure definitions		Cases	Controls	Matched OR (95% CI)^b
No medications^a		1,140 (25.6)	5,766 (32.4)	0.95 (0.86–1.04)
Number of non-opioid medications^a	1–2	673 (15.1)	3,155 (17.7)	1.00
	3–4	495 (11.1)	2,102 (11.8)	1.06 (0.94–1.19)
	≥5	1,563 (35.2)	5,659 (31.8)	1.10 (0.99–1.21)
New opioid analgesics use^c		104 (2.3)	113 (0.6)	2.04 (1.63–2.55)
No new, no frequent opioid analgesic use^d		243 (5.5)	690 (3.9)	1.25 (1.08–1.46)
Frequent opioid analgesics use^e	3–4	96 (2.2)	141 (0.8)	1.71 (1.36–2.14)
	5–6	42 (0.9)	63 (0.4)	1.69 (1.22–2.34)
	≥7	89 (2.0)	91(0.5)	1.71 (1.34–2.19)

^aWithin 1–180 days prior to the index date.
^bAdjusted for benzodiazepines, nervous/cardiovascular system medications and number of different medications dispensed within 1–30 days prior to the index date, weighted Charlson Comorbidity, marital status and occupation.
^cWhen ≥1 opioid analgesic dispensed within 1–30 days, but none within 31–180 days prior to the index date.
^dWhen 1–2 opioid analgesics dispensed within 31–180 days, or when one was given within 1–30 days and another within 31–180 days prior to the index date.
^eWhen ≥3 opioid analgesics dispensed within 1–180 days, with at least one within 31–180 days prior to the index date.

Table 3. Adjusted odds ratios for the exposure of new/recent and frequent opioid analgesic use on the risk of injurious single-vehicle crashes, stratified by sex and age group
Exposure definitions		Adjusted OR (95% CI)^a
Exposure definitions		Male	Female	50–64 years	65–80 years
1–2 non-opioid dispensations^b		1.00	1.00	1.00	1.00
New use^c		3.61 (2.44–5.33)	2.32 (1.38–3.88)	2.79 (1.93–4.02)	3.75 (2.06–6.80)
Frequent use (no. of dispensations)^d	3–4	2.79 (1.93–4.01)	1.48 (0.88–2.50)	1.85(1.24–2.76)	2.87 (1.81–4.55)
	5–6	1.69 (0.94–3.04)	3.36 (1.82–6.20)	2.36 (1.42–3.91)	2.08 (0.96–4.54)
	≥7	2.49 (1.61–3.87)	2.64 (1.53–4.52)	2.78 (1.84–4.21)	1.82 (0.97–3.40)

^aAdjusted for benzodiazepines, nervous/cardiovascular system medications and number of different medications dispensed within 1–30 days prior to the index date, weighted Charlson Comorbidity, marital status and occupation.
^bWithin 1–180 days prior to the index date.
^cWhen ≥1 opioid analgesic dispensed within 1–30 days, but none within 31–180 days prior to the index date.
^dWhen ≥3 opioid analgesics dispensed within 1–180 days, with at least one within 31–180 days prior to the index date.