Table 2.
Parkinson or Parkinson‐like symptoms and their association with previous influenza infections
| Idiopathic Parkinson’s disease | Parkinson’s disease‐like symptoms | |||||
|---|---|---|---|---|---|---|
| Cases (n = 3976) | Controls (n = 15 891) | OR (95% CI)* | Cases (n = 18 336) | Controls (n = 73 320) | OR (95% CI)* | |
| Number of influenza attacks† | ||||||
| 0 | 3753 (94·4) | 15 044 (94·6) | 1·0 | 16 794 (91·6) | 68 251 (93·1) | 1·0 |
| 1 | 196 (4·9) | 724 (4·6) | 1·08 (0·91–1·27) | 1298 (7·1) | 4426 (6·0) | 1·20 (1·12–1·28) |
| 2 | 23 (0·6) | 90 (0·6) | 1·03 (0·64–1·65) | 181 (1·0) | 498 (0·7) | 1·52 (1·28–1·81) |
| 3+ | 4 (0·1) | 33 (0·2) | 0·44 (0·14–1·32) | 63 (0·3) | 145 (0·2) | 2·00 (1·45–2·75) |
| Timing of last influenza attack† | ||||||
| 0 | 3753 (94·4) | 15 044 (94·7) | 1·0 | 16 794 (91·6) | 68 251 (93·1) | 1·0 |
| 1–29 | 5 (0·13) | 5 (0·03) | 4·33 (1·24–15·1) | 34 (0·2) | 46 (0·1) | 3·03 (1·94–4·74) |
| 30–364 | 16 (0·4) | 95 (0·6) | 0·64 (0·37–1·11) | 169 (0·9) | 509 (0·7) | 1·36 (1·14–1·63) |
| 365–729 | 22 (0·6) | 103 (0·6) | 0·84 (0·52–1·34) | 170 (0·9) | 537 (0·7) | 1·29 (1·08–1·54) |
| 730+ days | 180 (4·5) | 644 (4·1) | 1·13 (0·94–1·34) | 1169 (6·4) | 3977 (5·4) | 1·20 (1·12–1·29) |
| Severe influenza followed by clinical complications | ||||||
| 0 | 3753 (94·4) | 15 044 (94·7) | 1·0 | 16 794 (91·6) | 68 251 (93·1) | 1·0 |
| 1+ | 28 (0·7) | 126 (0·8) | 0·91 (0·60–1·38) | 255 (1·4) | 715 (1·0) | 1·45 (1·25–1·68) |
| Last severe influenza attack† | ||||||
| 0 | 3753 (94·4) | 15 044 (94·7) | 1·0 | 16 794 (91·6) | 68 251 (93·1) | 1·0 |
| 1–29 | 1 (0·03) | 1 (0·01) | 4·43 (0·27–73) | 8 (0·04) | 6 (0·01) | 5·30 (1·83–15·3) |
| 30–364 | 2 (0·05) | 19 (0·1) | 0·42 (0·10–1·82) | 29 (0·16) | 68 (0·1) | 1·76 (1·14–2·73) |
| 365–729 | 0 (0) | 13 (0·1) | – | 34 (0·2) | 93 (0·1) | 1·47 (0·99–2·18) |
| 730+ days | 25 (0·6) | 93 (0·6) | 1·09 (0·70–1·70) | 184 (1·0) | 548 (0·8) | 1·36 (1·15–1·61) |
*Adjusted for smoking status (non, current, ex, unknown) and BMI (<25, 25–29·9, 30+ kg/m2, unknown).
†Prior to the index date.