Table 2.

Association of changes in sleep quality and duration between the baseline and follow-up visit, and risk of parkinsonism and Parkinson’s disease

Determinant (unit)	Parkinsonism		Parkinson’s disease
	Cases/n	HR (95% CI)	Cases/n	HR (95% CI)
Change in sleep quality (worse sleep)	25/5206	1.23 (0.83–1.83)	17/5244	1.76 (1.12–2.78)
Change in sleep duration (shorter sleep)	25/5244	1.45 (0.99–2.13)	17/5238	1.72 (1.08–2.72)

Changes in sleep quality were modelled per standard deviation increase (‘worsening’) of global PSQI score, and changes for sleep duration were modeled as standard deviation decrease (‘shortening’) of sleep duration from the baseline visit to the follow-up visit. HR estimates are adjusted for age at baseline, sex, educational level, smoking status and time interval between measurements. Additional adjustment for depressive symptoms at baseline minimally changed point and interval estimates (data not shown). After additional adjustment for the average level of sleep quality or sleep duration of the two measurements, point and interval estimates for the relation with parkinsonism barely changed. Estimates for associations of change in sleep quality (HR 1.87, 95% CI 1.12–3.10) and change in sleep duration (HR 1.85, 95% CI 1.14–2.98) with risk of Parkinson’s disease increased. Estimates in bold indicate statistically significant results at P < 0.05.