Estimated prevalence and incidence of diagnosed ADHD and health care utilization in adults in Sweden – a longitudinal population-based register study

Figures & data

Table 1 Independent variables used in multiple linear regression with PDD as response variable

Variable	Value	Definition	Comment
Age	≥18 years	n/a	Age was used as a continuous variable
Sex	0= female, 1= male	n/a
Drug holiday	0= no, 1= yes	Gap between observations for a patient in the PDR that exceeds 90 days (ie, the grace period, associated with the common maximum prescription length in Sweden)
Expedition year	Starting year: 2006
ADHD diagnosisa	Disturbance of activity and attention (F90.0); DAMP (F90.0A); ADHD (F90.0B); activity and attention disturbance (F90.0C); activity and attention disturbance, unspecified (F90.0X); hyperkinetic conduct disorders (F90.1); other hyperkinetic disorders (F90.8); ADHD, unspecified type (F90.9); other specified emotional disorders with an onset in childhood or adolescence (F98.8)	Presence of diagnosis code in the NPR	All patients will, by definition, have at least one of the diagnoses
Region	Stockholm, west Sweden, south Sweden, mid-Sweden, north Sweden	Region where the patient lived during the study period
Comorbiditya	Autism (F84.0); atypical autism (F84.9); anxiety (F41.2–F41.9); Asperger syndrome (F84.5); bipolar disorder (F31.0–F31.9); depression (F33.0–F33.9); eating disorders (F50.8–F50.9); impulse control disorders (F63.8–F63.9); personality disorders (F60.0–F60.9); oppositional defiant disorders (F91.3); schizophrenia (F20.0–F23.2); substance use disorders (F10.2–F19.2)	Presence of any defined comorbidity
Add-on ADHD medicationb	0= no, 1= yes	Has received any other ADHD medication during the time period of OROS-MPH use	Amphetamine (N06BA01); dexamphetamine (N06BA02); atomoxetine (N06BA09); methylphenidate (OROS-MPH, MPH-IR, MPH-MR; N06BA04); modafinil (N06BA07)
Concomitant medicationsb	Antidepressants (N06AA02, N06AA04, N06AA06, N06AA09, N06AA10, N06AA21); antipsychotics (N05A-); anxiolytics (N05BA-, N05BB-); hypnotics (N05CC-, N05CD-, N05CF-, N05CH01); SSRIs (N06AB03, N06AB04, N06AB05, N06AB06, N06AB08, N06AB10); SNRIs (N06AX16, N06AX21); other (N06AX02, N06AX03, N06AX06, N06AX11, N06AX12, NO6AX18, NO6AX22)	Presence of any defined concomitant medication

Notes:

a Defined by code from International Statistical Classification of Diseases and Related Health Problems, Tenth Revision.¹³

b Defined by codes from anatomic therapeutic chemical classification system.³¹

Abbreviations: ADHD, attention-deficit/hyperactivity disorder; DAMP, deficits in attention, motor control, and perception; MPH-IR, immediate-release methylphenidate; MPH-MR, modified-release methylphenidate; n/a, not applicable; NPR, National Patient Register; OROS-MPH, osmotic release oral system methylphenidate; PDD, dispensed patient daily dose; PDR, Prescribed Drug Register; SNRI, serotonin–norepinephrine reuptake inhibitor; SSRI, selective serotonin reuptake inhibitor.

Table 2 Estimated prevalencea of diagnosed ADHD in adults, and characteristics of adult patients with an ADHD diagnosis, 2006–2011

	2006 (n=4,149)	2007 (n=6,888)	2008 (n=11,085)	2009 (n=15,414)	2010 (n=21,389)	2011 (n=26,820)
Age in years, mean (SD); median	30.8 (10.8); 29.0	31.1 (10.8); 29.0	31.5 (11.0); 29.0	31.5 (11.1); 29.0	31.9 (12.2); 29.0	31.7 (11.6); 29.0
Sex, n (%)
Male	2,592 (62.5)	4,208 (61.1)	6,529 (58.9)	8,903 (57.8)	12,015 (56.2)	14,808 (55.2)
Female	1,557 (37.5)	2,680 (38.9)	4,556 (41.1)	6,511 (42.2)	9,374 (43.8)	12,012 (44.8)
Age group, n (%)
18–21 years	1,109 (26.7)	1,738 (25.2)	2,690 (24.3)	3,797 (24.6)	5,380 (25.2)	6,678 (24.9)
22–64 years	3,026 (72.9)	5,131 (74.5)	8,361 (75.4)	11,572 (75.1)	15,745 (73.6)	20,000 (74.6)
≥65 years	14 (0.3)	19 (0.3)	34 (0.3)	45 (0.3)	264 (1.2)	142 (0.5)
Estimated prevalence per 1,000 persons, by age group	0.58	0.95	1.51	2.07	2.85	3.54
18–21 years	2.42	3.65	5.40	7.33	10.20	12.67
22–64 years	0.59	0.99	1.61	2.22	3.01	3.81
≥65 years	0.01	0.01	0.02	0.03	0.15	0.08

Notes:

a Swedish population from November 2006–2011: Total, 2006: 7,190,792; 2007: 7,261,025; 2008: 7,342,036; 2009: 7,429,061; 2010: 7,507,516; 2011: 7,574,814; age 18–21 years, 2006: 457,478; 2007: 475,707; 2008: 497,843; 2009: 517,732; 2010: 527,248; 2011: 527,133; age 22–64 years, 2006: 5,138,439; 2007: 5,163,520; 2008: 5,185,548; 2009: 5,207,670; 2010: 5,229,188; 2011: 5,249,647; age ≥65 years, 2006: 1,594,875; 2007: 1,621,798; 2008: 1,658,645; 2009: 1,703,659; 2010: 1,751,080; 2011: 1,798,034.³³

Abbreviation: ADHD, attention-deficit/hyperactivity disorder.

Table 3 Estimated incidencea and characteristics of newly diagnosed adult patients, 2007–2011

	2007 (n=2,809)	2008 (n=4,083)	2009 (n=4,831)	2010 (n=6,382)	2011 (n=6,816)
Age in years, mean (SD); median	31.4 (10.7); 29.0	31.7 (10.8); 30.0	31.8 (11.0); 29.0	33.4 (14.0); 30.0	32.4 (11.9); 30.0
Sex, n (%)
Male	1,695 (60.3)	2,345 (57.4)	2,726 (56.4)	3,442 (53.9)	3,621 (53.1)
Female	1,114 (39.7)	1,738 (42.6)	2,105 (43.6)	2,940 (46.1)	3,195 (46.9)
Age group, n (%)
18–21 years	625 (22.2)	868 (21.3)	997 (20.6)	1,353 (21.2)	1,431 (21.0)
22–64 years	2,176 (77.5)	3,203 (78.4)	3,815 (79.0)	4,811 (75.4)	5,315 (78.0)
≥65 years	8 (0.3)	12 (0.3)	19 (0.4)	218 (3.4)	70 (1.0)
Estimated incidence per 1,000 persons, by age group	0.39	0.56	0.65	0.85	0.90
18–21 years	1.31	1.74	1.93	2.57	2.71
22–64 years	0.42	0.62	0.73	0.92	1.01
≥65 years	<0.01	0.01	0.01	0.12	0.04

Notes:

a Swedish population from November 2007–2011: Total, 2007: 7,261,025; 2008: 7,342,036; 2009: 7,429,061; 2010: 7,507,516; 2011: 7,574,814; age 18–21 years; 2007: 475,707; 2008: 497,843; 2009: 517,732; 2010: 527,248; 2011: 527,133; age 22–64 years; 2007: 5,163,520; 2008: 5,185,548; 2009: 5,207,670; 2010: 5,229,188; 2011: 5,249,647; age ≥65 years; 2007: 1,621,798; 2008: 1,658,645; 2009: 1,703,659; 2010: 1,751,080; 2011: 1,798,034.³³

Abbreviation: ADHD, attention-deficit/hyperactivity disorder.

Table 4 Most common comorbidities in adult patients with an ADHD diagnosis from 2006 to 2011 (cross-sectional dataset, N=44,364) and in newly diagnosed adult patients from 2007 to 2011 (longitudinal dataset, N=24,921)

Comorbidity, n (%)	All patients with ADHD and ≥1 comorbidity (n=23,344)				Newly diagnosed patients with ≥1 comorbidity (n=13,447)
	N	% by comorbiditya	% by patients with ≥1 comorbidityb	% by complete datasetc	N	% by comorbiditya	% by patients with ≥1 comorbidityb	% by complete datasetc
Anxiety	9,109	25.3	39.0	20.5	5,467	26.5	40.7	21.9
Substance use disorder	6,905	19.2	29.6	15.6	3,873	18.8	28.8	15.5
Depression	6,184	17.2	26.5	13.9	3,628	17.6	27.0	14.6
Personality disorder	3,835	10.6	16.4	8.6	2,262	11.0	16.8	9.1
Asperger syndrome	3,587	10.0	15.4	8.1	1,900	9.2	14.1	7.6
Bipolar disorder	3,349	9.3	14.3	7.5	1,981	9.6	14.7	7.9
Autismd	1,248	3.5	5.3	2.8	569	2.8	4.2	2.3
Schizophrenia	1,112	3.1	4.8	2.5	559	2.7	4.2	2.2
Eating disorder	611	1.7	2.6	1.4	365	1.8	2.7	1.5
Impulse control disorder	60	0.2	0.3	0.1	28	0.1	0.2	0.1
Oppositional defiant disorder	43	0.1	0.2	0.1	7	<0.1	<0.1	<0.1

Notes:

a Denominator for percentages is the total number of comorbidities (n=36,043 [all patients], n=20,639 [newly diagnosed patients]).

b Denominator for percentages is the total number of patients with ADHD and ≥1 comorbidity (n=23,344 [all patients], n=13,447 [newly diagnosed patients]).

c Denominator for percentages is the total number of patients in the dataset (n=44,364 [all patients], n=24,921 [newly diagnosed patients]).

d Includes atypical autism.

Abbreviation: ADHD, attention-deficit/hyperactivity disorder.

Table 5 Characteristics of pharmacologically treated and non-pharmacologically treated adult patients with ADHD

	All patients with diagnosed ADHD		Newly diagnosed ADHD patients
	Pharmacologically treated	No treatment	Pharmacologically treated	No treatment
Share of total, n (%)	34,987 (78.9)	9,377 (21.1)	16,365 (65.7)	8,556 (34.3)
Sex, n (%)
Male	19,989 (78.4)a	5,510 (21.6)a	8,891 (64.3)b	4,938 (35.7)b
Female	14,998 (79.5)c	3,867 (20.5)c	7,474 (67.4)d	3,618 (32.6)d
Age group, n (%)
18–21 years	11,270 (77.8)e	3,214 (22.2)e	3,349 (63.5)f	1,925 (36.5)f
22–64 years	23,611 (80.0)e	5,896 (20.0)e	12,976 (67.2)f	6,344 (32.8)f
≥65 years	106 (28.4)e	267 (71.6)e	40 (12.2)f	287 (87.8)f

Notes:

a Denominator is the total number of males (with or without treatment) for all patients.

b Denominator is the total number of males (with or without treatment) for newly diagnosed patients.

c Denominator is the total number of females (with or without treatment) for all patients.

d Denominator is the total number of females (with or without treatment) for newly diagnosed patients.

e Denominator is the total number in the age group (with or without treatment) for all patients.

f Denominator is the total number in the age group (with or without treatment) for newly diagnosed patients.

Abbreviation: ADHD, attention-deficit/hyperactivity disorder.

Table 6 Patient daily dose and defined daily dose of OROS-MPH among all adult patients with diagnosed ADHD treated with OROS-MPH during the study period (cross-sectional dataset; 2006–2011)

	Mean (SD) patient daily dose, mg	Defined daily dose, mg	95% confidence limits (mg)
Total (n=21,926)	51.5 (31.0)	1.72	51.1, 51.9
Males (n=12,025)	54.4 (33.3)a	1.81	53.8, 55.0
Females (n=9,901)	47.9 (27.7)	1.60	47.4, 48.5
Age group
18–21 years (n=4,942)	42.9 (21.5)b	1.43	42.3, 43.5
22–64 years (n=16,930)	53.9 (32.9)	1.80	53.5, 54.4
≥65 years (n=54)	53.5 (34.9)	1.78	44.0, 63.1

Notes:

a p<0.05 for comparison with females.

b p<0.05 for comparisons with 22–64 years and ≥65 years. The patient daily dose is the average daily amount of a drug that is actually prescribed. The defined daily dose is the assumed average maintenance dose per day for a drug used for its main indication in adults.³¹ The independent t-test was used to identify potential statistical differences in the mean dose between sexes, and analysis of variance was used to identify potential statistical differences in the mean dose between age groups.

Abbreviations: ADHD, attention-deficit/hyperactivity disorder; OROS-MPH, osmotic release oral system methylphenidate.

Table 7 Proportions of patients receiving OROS-MPH <1 DDD, 1–2 DDDs, and ≥2 DDDs during the study period (cross-sectional dataset)

	<1 DDD	1–2 DDDs	≥2 DDDs
N (%) of adults with diagnosed ADHD who reported use of OROS-MPH treatmenta	5,476 (25.0)	9,951 (45.4)	6,499 (29.6)
Malesb	2,716 (49.6)	5,326 (53.5)	3,983 (61.3)
Femalesb	2,760 (50.4)	4,625 (46.5)	2,516 (38.7)
Age group, n (%)a
18–21 years	1,470 (29.7)	2,587 (52.3)	885 (17.9)
22–64 years	3,992 (23.6)	7,339 (43.3)	5,599 (33.1)
≥65 years	14 (26.0)	25 (46.3)	15 (27.8)

Notes: 1 DDD³¹ =30 mg MPH.

a Denominators for percentages in this row are the total number of patients included in the row.

b Denominators for percentages in this row are the total number of patients per DDD group (<1 DDD, 1–2 DDDs, ≥2 DDDs).

Abbreviations: ADHD, attention-deficit/hyperactivity disorder; DDD, defined daily dose; OROS-MPH, osmotic release oral system methylphenidate.

Table 8 Estimates of coefficients for the estimated change in PDD of OROS-MPH (final regression model)

Variable	Change in PDD of OROS-MPH (%)a	95% CI (%)a		p-value
Age at current prescription	0.587	0.527	0.647	<0.0001
Male sex	10.783	9.453	12.113	<0.0001
Expedition year	6.545	6.032	7.057	<0.0001
Drug holidayb	15.165	13.814	16.515	<0.0001
ADHD diagnosis F90.0B	4.037	2.663	5.412	<0.0001
ADHD diagnosis F90.0C	−4.795	−6.945	−2.645	<0.0001
Region: Stockholm	−9.866	−11.422	−8.310	<0.0001
Region: West Sweden	−5.046	−6.768	−3.323	<0.0001
Anxiety	−2.115	−3.737	−0.494	0.0106
Depression	−1.931	−3.767	−0.094	0.0394
Bipolar disorder	−5.791	−8.180	−3.402	<0.0001
Personality disorder	4.803	2.549	7.057	<0.0001
Asperger syndrome	−2.840	−5.151	−0.529	0.0160
Substance use disorder	18.010	16.210	19.810	<0.0001
Add-on medication	18.392	16.867	19.917	<0.0001
Concomitant medication: antipsychotics	5.911	4.299	7.523	<0.0001
Concomitant medication: hypnotics	4.514	3.095	5.933	<0.0001
Concomitant medication: SNRI	1.750	0.108	3.393	0.0367

Notes: F90.0B: ADHD; F90.0C: Activity and attention disturbance; F90.0X: Activity and attention disturbance, unspecified.

a North Sweden and expedition year 2006 used as reference.

b A gap between observations for a patient in the Prescribed Drug Register exceeding 90 days.

Abbreviations: ADHD, attention-deficit/hyperactivity disorder; OROS-MPH, osmotic release oral system methylphenidate; PDD, dispensed patient daily dose; SNRI, serotonin–norepinephrine reuptake inhibitor.

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