Table 1.

Summary of case‐control studies on dietary exposure in essential tremor

Categories	Authors	Year	Sample size	Country	Exposure	Results
Antioxidants	Scarmeas & Louis 52	2007	148 ET, 250 controls	USA	Mediterranean diet	Higher adherence to diet was associated with lower odds for ET [0.78 (0.61–0.99); P = 0.042]. Compared to lowest adherence tertile, middle tertile [0.41 (0.16–1.05)], and highest tertile [0.29 (0.10–0.82)] had a lower ET odds [P for trend 0.021]
	Louis et al. 51	2005	156 cases, 220 controls	USA	Vitamin E, vitamin C	No significant difference in vitamin E and C consumption between ET cases and controls
Meat (harmane)	Louis et al. 46	2008	125 cases, 125 controls	USA	Meat consumptions, meat doneness level	Higher total current meat consumption was associated with ET (OR = 1.006, P = 0.04) only in male ET cases. Male cases had higher odds of being in the highest than lowest quartile of total current meat consumption (adjusted OR = 21.36, P = 0.001). No significant difference between meat doneness level in cases and controls.
	Louis et al. 45	2005	106 cases, 161 controls	USA	Blood harmane concentration, animal protein intake	Higher log (blood harmane concentration) in ET cases than controls. Similar amounts of animal protein consumption and caloric intakes in ET cases and controls.
Harmane	Louis et al. 38	2013	130 cases, 138 controls	Spain	Blood harmane concentration	Blood harmane concentrations higher in ET compared to controls, but did not reach statistical significance
	Louis et al. 40	2013	70 cases, 27 controls	USA	Brain harmane concentration	Mean brain harmane concentration was higher in ET than controls. Mean concentration was 35% higher in ET cases compared to controls after adjustment for postmortem interval and freezer time.
	Louis et al. 37	2008	150 cases, 135 controls	USA	Blood harmane concentration	Higher Log (blood harmane concentration) in ET compared to controls (ORadjusted 1.56, 95% CI 1.01–2.42, P = 0.04) Higher odds of ET OR 1.90 (95% CI 1.07–3.39, P = 0.029) in highest vs. lowest log (blood harmane concentration) tertile.
	Louis et al. 36	2002	100 cases, 100 controls	USA	Blood harmane concentration	Higher mean log (blood harmane concentration) in cases than controls. Median harmane = 5.21 g(−10)/mL in cases and 2.28 g(−10)/mL in controls) (P = 0.005).
Caffeine	Prakash et al. 66	2006	79 cases, 100 controls	Singapore	Caffeine consumption	Caffeine consumption in ET patients higher than control group (nonsignificant in multivariate analysis). No significant correlation with disease duration or total tremor score in ET patients
	Louis et al. 57	2004	130 cases, 175 controls	USA	Caffeine consumption	No correlation between daily caffeine intake in milligrams and disease duration, total tremor score, or performance‐based test score in ET cases.