Frozen Shoulder and the Risk of Parkinson’s Disease: A Danish Registry-Based Cohort Study

Figures & data

Table 1 Characteristics of the Frozen Shoulder Cohort, the General Population Comparison Cohort, and the Back Pain Comparison Cohort

	Frozen Shoulder Cohort	General Population Cohort	Back Pain Cohort
No. of observations	37,041 (100.0)	370,410 (100.0)	111.101 (100.0)
Sex
Male	15,991 (43.2)	159,910 (43.2)	47,962 (43.2)
Female	21,050 (56.8)	210,500 (56.8)	63,139 (56.8)
Age in years
0–39		973 (0.3)	317 (0.3)
40–59	25,311 (68.3)	252,003 (68.0)	75,580 (68.0)
60–69	7,700 (20.8)	77,070 (20.8)	23,130 (20.8)
70–79	2995 (8.1)	29,959 (8.1)	8983 (8.1)
80 +	1035 (2.8)	10,405 (2.8)	3091 (2.8)
Index year
1995–2004	9403 (25.4)	94,030 (25.4)	28,196 (25.4)
2005–2013	18,884 (51.0)	188,840 (51.0)	56,646 (51.0)
2014–2016	8754 (23.6)	87,540 (23.6)	26,259 (23.6)
Type of hospital diagnosis of frozen shoulder
Primary diagnosis	33,237 (89.7)	–	–
Secondary diagnosis	3804 (10.3)	–	–
Inpatient	2765 (7.5)	–	–
Outpatient	34,173 (92.3)	–	–
Half day patient	103 (0.3)	–	–
Comorbidities
Chronic obstructive pulmonary disease	2368 (6.4)	17,633 (4.8)	10,953 (9.9)
Myocardial infarction	1108 (3.0)	7875 (2.1)	3665 (3.3)
Stroke	1481 (4.0)	10,906 (2.9)	5249 (4.7)
Thyroid disease	1091 (2.9)	7878 (2.1)	3632 (3.3)
Shoulder trauma	10,696 (28.9)	17,076 (4.6)	11,300 (10.2)
Shoulder surgery	5794 (15.6)	8935 (2.4)	5747 (5.2)
Autoimmune disease	4238 (11.4)	28,803 (7.8)	18,583 (16.7)
Dementia	108 (0.3)	1403 (0.4)	697 (0.6)
Diabetes	3987 (10.8)	13,592 (3.7)	6908 (6.2)
Congestive heart failure	649 (1.8)	4623 (1.2)	2721 (2.4)
Peripheral vascular disease	949 (2.6)	6248 (1.7)	4225 (3.8)
Cerebrovascular disease	1752 (4.7)	13,079 (3.5)	6496 (5.8)
Ulcer disease	880 (2.4)	6141 (1.7)	4439 (4.0)
Mild liver disease	295 (0.8)	3020 (0.8)	1886 (1.7)
Hemiplegia	75 (0.2)	591 (0.2)	384 (0.3)
Moderate to severe renal disease	400 (1.1)	2908 (0.8)	1790 (1.6)
Any tumor	2040 (5.5)	18,629 (5.0)	7057 (6.4)
Leukemia	62 (0.2)	432 (0.1)	209 (0.2)
Lymphoma	118 (0.3)	1174 (0.3)	719 (0.6)
Moderate to severe liver disease	63 (0.2)	657 (0.2)	414 (0.4)
Metastatic solid tumor	181 (0.5)	1695 (0.5)	1104 (1.0)
AIDS	26 (0.1)	337 (0.1)	94 (0.1)

Figure 1 Cumulative incidence plot. Cumulative incidence of death from index date and over 20 years of follow up for the cohort of population comparators, the frozen shoulder cohort, and the back pain cohort. Curves were smoothed for data protection.

Table 2 Cumulative Incidence of Parkinson’s Disease

Follow up Period	No. of individuals at Risk at the Beginning of the Period	No. of Incident Parkinson’s Disease Diagnoses	Cumulative risk (%)^a	95% confidence Interval (%)
Frozen shoulder cohort
0–1 years	37,041	21	0.06	0.04–0.09
1–3 years	33,929	44	0.14	0.10–0.19
1–6 years	33,929	75	0.27	0.21–0.34
1–10 years	33,929	117	0.55	0.45–0.67
1–22 years	33,929	163	1.47	1.15–1.85
0–22 years	37,041	184	1.51	1.19–1.89
General population cohort
0–1 years	370,410	101	0.03	0.02–0.03
1–3 years	338,581	246	0.08	0.07–0.09
1–6 years	338,581	534	0.20	0.19–0.22
1–10 years	338,581	796	0.38	0.35–0.41
1–22 years	338,581	1128	1.01	0.92–1.11
0–22 years	370,410	1229	1.03	0.94–1.13
Back pain cohort
0–1 years	111,101	71	0.07	0.05–0.08
1–3 years	100,262	115	0.13	0.11–0.15
1–6 years	100,262	233	0.30	0.26–0.34
1–10 years	100,262	337	0.52	0.47–0.59
1–22 years	100,262	450	1.28	1.11–1.48
0–22 years	111,101	521	1.32	1.15–1.51

Note: ^aTreating death as a competing risk.

Figure 2 Cumulative incidence plot. Cumulative incidence Parkinson’s disease from index date and over 20 years of follow up for the cohort of population comparators, the frozen shoulder cohort, and the back pain cohort. Curves were smoothed for data protection.

Table 3 Incidence Rates and Hazard Ratios for Parkinson’s Disease, Comparing the Frozen Shoulder Cohort to the General Population and Back Pain Cohorts

	Follow-up Period	No. of Incident Parkinson’s Disease Diagnoses ^a	Incidence Rate (per 1000PYRs) (95% CI)	Unadjusted Hazard Ratio (95% CI)	Adjusted Hazard Ratio (95% CI) ^b	Adjusted Hazard Ratio (95% CI) ^c
FROZEN SHOULDER COHORT VS GENERAL POPULATIO COHORT	General population cohort
	0–1 year	100	0.28 (0.23–0.34)	-	-	-
	1–3 years	245	0.41 (0.36–0.46)	-	-	-
	3–6 years	290	0.43 (0.38–0.48)	-	-	-
	6–10 years	260	0.48 (0.42–0.54)	-	-	-
	10–22 years	330	0.69 (0.61–0.76)	-	-	-
	1–22 years	1130	0.49 (0.46–0.52)	-	-	-
	0–22 years	1230	0.46 (0.44–0.49)	-	-	-
	Frozen shoulder cohort
	0–1 year	20	0.59 (0.37–0.87)	2.09 (1.31–3.35)	1.94 (1.20–3.13)	1.92 (1.19–3.12)
	1–3 years	45	0.72 (0.53–0.95)	1.79 (1.30–2.48)	1.78 (1.28–2.46)	1.77 (1.28–2.46)
	3–6 years	30	0.46 (0.31–0.64)	1.08 (0.74–1.57)	1.04 (0.71–1.52)	1.04 (0.71–1.52)
	6–10 years	40	0.77 (0.55–1.01)	1.66 (1.19–2.32)	1.62 (1.15–2.27)	1.60 (1.14–2.25)
	10–22 years	45	0.96 (0.71–1.26)	1.34 (0.97–1.84)	1.26 (0.91–1.75)	1.28 (0.92–1.78)
	1–22 years	165	0.71 (0.60–0.82)	1.44 (1.22–1.71)	1.40 (1.19–1.66)	1.40 (1.18–1.66)
	0–22 years	185	0.69 (0.60–0.80)	1.50 (1.28–1.76)	1.45 (1.24–1.70)	1.44 (1.23–1.69)
FROZEN SHOULDER COHORT VS BACK PAIN COHORT	Back pain cohort
	0–1 year	70	0.67 (0.53–0.84)	-	-	-
	1–3 years	115	0.64 (0.53–0.77)	-	-	-
	3–6 years	120	0.61 (0.51–0.73)	-	-	-
	6–10 years	105	0.67 (0.55–0.80)	-	-	-
	10–22 years	115	0.84 (0.69–1.00)	-	-	-
	1–22 years	450	0.68 (0.62–0.74)	-	-	-
	0–22 years	520	0.68 (0.62–0.74)	-	-	-
	Frozen shoulder cohort
	0–1 year	20	0.59 (0.37–0.87)	0.87 (0.53–1.41)	0.89 (0.54–1.46)	0.94 (0.56–1.58)
	1–3 years	45	0.72 (0.53–0.95)	1.09 (0.77–1.55)	1.09 (0.76–1.55)	1.08 (0.75–1.56)
	3–6 years	30	0.46 (0.31–0.64)	0.75 (0.50–1.14)	0.76 (0.50–1.15)	0.77 (0.50–1.17)
	6–10 years	40	0.77 (0.55–1.01)	1.17 (0.80–1.71)	1.20 (0.81–1.76)	1.25 (0.84–1.86)
	10–22 years	45	0.96 (0.71–1.26)	1.14 (0.78–1.67)	1.24 (0.82–1.87)	1.26 (0.83–1.90)
	1–22 years	165	0.71 (0.60–0.82)	1.03 (0.85–1.24)	1.03 (0.85–1.25)	1.04 (0.86–1.26)
	0–22 years	185	0.69 (0.60–0.80)	1.01 (0.84–1.20)	1.01 (0.84–1.21)	1.02 (0.85–1.22)

Notes: ^a Rounded to nearest 5, ^b Adjusted for chronic obstructive pulmonary disease, autoimmune disease, thyroid disease, dementia, and diabetes, ^c Adjusted for chronic obstructive pulmonary disease, autoimmune disease, thyroid disease, dementia, diabetes, and Charlson comorbidity index.

Abbreviations: PYRs, Person-years; CI, Confidence interval.

Data Sharing Statement

To protect the privacy of patients, it is by Danish law prohibited to make individual-level data publicly available.