Table 4.

Noise exposure and the risk of stroke: summary of findings.

Noise Source	Outcome $	Number of Study Design (s) *	RR † per 10 dB (95% CI)	Participants (Cases)	Quality of Evidence ‡
Air traffic	Prev	2 CS	1.02 (0.80–1.28)	14,098 (151)	$\oplus$
	Inc	2 ECO	1.05 (0.96–1.15)	9,619,082 (97,949)	$\oplus$
	Mort	2 ECO	1.07 (0.98–1.17)	3,897,645 (12,086)	$\oplus$
		1 CO	0.99 (0.94–1.04)	4,580,311 (25,231)	$\oplus \oplus \oplus$
Road traffic	Prev	2 CS	1.00 (0.91–1.10)	14,098 (151)	$\oplus$
	Inc	1 CO	1.14 (1.03–1.25)	51,485 (1881)	$\oplus \oplus \oplus$
	Mort	3 CO	0.87 (0.71–1.06)	581,517 (2634)	$\oplus \oplus \oplus$
Rail traffic	Prev	1 CS	1.07 (0.92–1.25)	9365 (89)	$\oplus$

^$ Outcome: Prev = prevalence of stroke, Inc = incidence of stroke, Mort = mortality due to stroke; * ECO = ecological study, CS = cross-sectional study, CO = cohort study; ^†: RR = Relative risk per 10 decibel (dB change in noise level, 95% CI = 95% Confidence Interval. The noise levels are expressed in L_DEN; ^‡ GRADE Working Group Grades of Evidence: High quality (⊕⊕⊕⊕): Further research is very unlikely to change our confidence in the estimate of effect, Moderate Quality (⊕⊕⊕): Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate, Low Quality (⊕⊕): Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate, Very low quality (⊕): We are very uncertain about the estimate.