Month of birth and the risk of narcolepsy: a systematic review and meta-analysis

Chih-Wei Hsu; Ping-Tao Tseng; Yu-Kang Tu; Pao-Yen Lin; Liang-Jen Wang; Chi-Fa Hung; Yao-Hsu Yang; Hung-Yu Kao; Chin-Bin Yeh; Hsiao-Ching Lai; Tien-Yu Chen

doi:10.5664/jcsm.9816

Month of birth and the risk of narcolepsy: a systematic review and meta-analysis

J Clin Sleep Med. 2022 Apr 1;18(4):1113-1120. doi: 10.5664/jcsm.9816.

Authors

Chih-Wei Hsu^{1

2}, Ping-Tao Tseng^{3

4}, Yu-Kang Tu^{5

6}, Pao-Yen Lin^{1

7}, Liang-Jen Wang^{8

9}, Chi-Fa Hung¹, Yao-Hsu Yang^{10

11

12}, Hung-Yu Kao², Chin-Bin Yeh¹³, Hsiao-Ching Lai¹³, Tien-Yu Chen^{13

14}

Affiliations

¹ Department of Psychiatry, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.
² Department of Computer Science and Information Engineering, National Cheng Kung University, Tainan, Taiwan.
³ Prospect Clinic for Otorhinolaryngology and Neurology, Kaohsiung, Taiwan.
⁴ Institute of Biomedical Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan.
⁵ Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Taipei, Taiwan.
⁶ Department of Dentistry, National Taiwan University Hospital, Taipei, Taiwan.
⁷ Institute for Translational Research in Biomedical Sciences, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, Taiwan.
⁸ Department of Child and Adolescent Psychiatry, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.
⁹ Department of Chinese Medicine, College of Medicine, Chang Gung University, Taoyuan, Taiwan.
¹⁰ Health Information and Epidemiology Laboratory, Chang Gung Memorial Hospital, Chiayi County, Taiwan.
¹¹ Department of Traditional Chinese Medicine, Chang Gung Memorial Hospital, Chiayi County, Taiwan.
¹² School of Traditional Chinese Medicine, College of Medicine, Chang Gung University, Taoyuan, Taiwan.
¹³ Department of Psychiatry, Tri-Service General Hospital, School of Medicine, National Defense Medical Center, Taipei, Taiwan.
¹⁴ Institute of Brain Science, National Yang Ming Chiao Tung University, Taipei 114, Taiwan, Taiwan.

Abstract

Study objectives: The aim of this study is to evaluate the relationship between the month of birth (MOB) and the risk of narcolepsy.

Methods: We conducted a systematic review of the electronic databases PubMed, Embase, and Cochrane CENTRAL from their inception to September 30, 2021. We also added data on narcolepsy from the National Health Insurance Research Database in Taiwan. Then we extracted the relative risk (RR) ratios of narcolepsy in each month of birth to those of the general population and transformed them from MOB to season. A random-effects model was used to calculate pooled RR ratios from the meta-analysis and 95% confidence interval (CI).

Results: The meta-analysis analyzed 7 studies and included 3,776 patients from 8 areas (Canada, China, France, Germany, Hong Kong, Netherlands, Taiwan, and United States). The RR ratio was highest in March (1.11; 95% CI, 0.99-1.26) and August (1.11; 95% CI, 0.98-1.26) and lowest in April (0.90; 95% CI, 0.78-1.03). However, none of the MOBs reached statistical significance. Moreover, the narcolepsy risk patterns on the 3 continents (Asia, Europe, and North America) were different. In North America, the highest and lowest significant risks were found in March (1.47; 95% CI, 1.20-1.79) and September (0.75; 95% CI, 0.56-0.99). In Asia, the lowest notable risk was in April (0.80; 95% CI, 0.66-0.97). In Europe, the risk of narcolepsy was not significantly related to any MOB. In terms of seasons, only spring MOBs in North America had a significantly higher risk (1.21; 95% CI, 1.06-1.38).

Conclusions: The findings indicated that the risk of narcolepsy and MOB differed across the 3 continents. This study indicates the important role of environmental factors in narcolepsy.

Systematic review registration: Registry: PROSPERO; Identifier: CRD42020186660.

Citation: Hsu C-W, Tseng P-T, Tu Y-K, et al. Month of birth and the risk of narcolepsy: a systematic review and meta-analysis. J Clin Sleep Med. 2022;18(4):1113-1120.

Keywords: meta-analysis; month of birth; narcolepsy; seasonality; systematic review.

Publication types

Meta-Analysis
Systematic Review
Research Support, Non-U.S. Gov't

MeSH terms

Hong Kong
Humans
Narcolepsy* / epidemiology
Narcolepsy* / etiology
Netherlands
Odds Ratio
Seasons