Seasonal variations of lithium plasma levels

Plasma Lithium Levels in a General Population: A Cross-Sectional Analysis of Metabolic and Dietary Correlates

Initial evidence suggests that lithium might affect life expectancy and the risk for different disease conditions, but most studies were conducted in patients on lithium medication. Little is known about the association of blood lithium levels within the physiological range with cardiometabolic risk factors and diet. We measured plasma lithium in a community-based sample from Northern Germany (samples taken between 2010 and 2012). All participants (aged 25-82 years) underwent standardized examinations and completed a semi-quantitative food frequency questionnaire. Of several variables tested, the estimated glomerular filtration rate (eGFR) was statistically significantly (inversely) associated with lithium levels, mainly in individuals with slightly impaired renal function (eGFR < 75 mL/min/1.73 m²). Besides, lithium levels were positively associated with age and alcohol intake. Using reduced rank regression, we identified a dietary pattern explaining 8.63% variation in plasma lithium levels. Higher lithium levels were associated with higher intakes of potatoes, leafy vegetables, root vegetables, fruits, tea, beer, wine and dietetic products and lower intakes of pasta, rice, pork, chocolate, sweets, soft drinks, other alcoholic beverages, sauces and snacks. Our observations suggest that plasma lithium levels are associated inversely with kidney function, particularly in individuals with slightly impaired renal function, and positively with age and alcohol intake. Lithium at physiological levels was moderately related to an exploratory dietary pattern.

Seasonal and temperature effect on serum lithium concentrations

BACKGROUND

Lithium remains the gold standard treatment for bipolar disorder. However, it has a very narrow therapeutic index (0.6-0.8 mmol/L). It has been suggested that high environmental temperature can lead to dehydration, elevated plasma lithium concentration and then lithium toxicity.

OBJECTIVES

We aimed to investigate the effect of seasonal and short-term changes in temperature on serum lithium concentrations in Sydney, Australia.

METHODS

We retrospectively analysed data from all patients who had serum lithium concentrations taken from the Prince of Wales and Sutherland Hospitals between 2008 and 2018. Temperature data came from the Bureau of Meteorology. We examined correlations between lithium concentrations and the preceding 5 days maximum temperatures, month and season. We also performed a longitudinal analysis of the effect of temperature and seasons within selected patients who had repeated levels.

RESULTS

A total of 11,912 serum lithium concentrations from 2493 patients were analysed. There was no significant association between higher lithium concentration and preceding higher temperatures (r = -0.008, p = 0.399). There was also no important seasonal or monthly variation, across all patients or in the smaller cohort with longitudinal data (n = 123, r = 0.008, 95% confidence interval: [-0.04, 0.06]).

CONCLUSION

There were no clinically important differences in serum lithium concentration related to seasons, months or temperatures, which suggests that patients on lithium are able to adequately maintain hydration during hot weather in Sydney.

Effect of age on the severity of chronic lithium poisoning

Objectives: Severe lithium toxicity is commonly observed in older people. We aimed to determine the extent to which age is associated with increased severity of chronic lithium poisoning and of which a range of possible factors might explain the associations.Method: We did a retrospective review of patients aged ≥15 years old with serum lithium concentrations ≥1.3 mmol/L from three hospitals. Clinical details, treatment and outcomes were recorded. eGFR, creatinine and lithium clearance were calculated. The severity of lithium toxicity was graded into five categories (Amdisen score). ANOVA was used to quantify the association between age and severity. Spearman correlation coefficient was used to explore relationships between age and different factors expected to alter severity. Ordinal regression analysis was used to determine the interdependence of age and these factors and age on severity of lithium toxicity.Results: From 2008-2018, there were 242 patients with a median age of 56.5 years (IQR: 41-69). There were 156 females (64%). There was a statistically significant association between Amdisen severity scores and age (p = .0004). The median calculated eGFR was 65 mL/min/1.73 m² (IQR: 41-91) with a corresponding estimated lithium clearance of 18 mL/min (IQR: 13.8-22.8). There was no correlation of age with initial serum lithium concentration (p = .76). There was a strong correlation between age and estimated lithium clearance (r = -0.72, 95% CI: -0.78 to -0.66, p < .001), lithium daily dose (r = -0.65, 95% CI: -0.72 to -0.57, p < .0001) and lithium concentration/dose (r = 0.62, 95% CI: 0.53-0.69, p < .0001). There was a weak correlation between age and infection (r = 0.18, 95% CI: 0.04-0.31, p = .009) and drug interactions (r = 0.25, 95% CI: 0.11-0.37, p = .0003). Ordinal regression indicated the independent predictors for severity of lithium toxicity were lithium concentration (p < .0001) and lithium clearance (p = .03) adjusted for age and dose.Conclusions: Despite lower lithium doses, older patients had more severe toxicity. Increased severity of lithium toxicity in the elderly is largely explainable by decreased lithium clearance from multiple factors such as age-related decline in renal function, drug interactions and infection.

Is environmental temperature related to renal symptoms, serum lithium levels, and other laboratory test results in current lithium users?

OBJECTIVE

Lithium continues to be an important mood disorder treatment. Although patients exposed to higher environmental temperatures may have serum lithium level elevations due to dehydration, there is conflicting data in the literature. In addition, no study has assessed the association between temperature and other renal laboratory tests and symptoms in lithium users.

METHODS

This is a cross-sectional analysis of 63 current lithium users who participated in the McGill Geriatric Lithium-induced Diabetes Insipidus Clinical Study. The relationship between mean daily temperature with diabetes insipidus symptoms, glomerular filtration rate, urine osmolality, serum sodium, lithium level, and lithium dose-level ratio was assessed.

RESULTS

Although a higher temperature on the day of laboratory testing trended toward being independently associated with a lower lithium dose-level ratio (Beta = -0.17, p = 0.08), this was not found when using a dichotomous measure of temperature (T > 20°C). No association was observed between temperature and other renal parameters.

CONCLUSIONS

The association of temperature with lithium levels, renal symptoms, and laboratory tests appears to be of relatively little clinical importance in lithium users in temperate climates. However, future research should re-examine patients living in climates with extreme temperatures (e.g., >40°C), who may theoretically be at higher risk.

The impact of environmental temperature on lithium serum levels

OBJECTIVES

Three studies have reported a seasonal variation in lithium serum levels, with higher levels during summer. Our objective was to investigate the impact of actual environmental temperature on lithium serum levels.

METHODS

A retrospective study was conducted using available records of lithium serum levels for the period between January 1995 and July 2004, obtained from three large teaching hospitals in The Netherlands. Lithium serum levels were linked to season and average daily temperature data obtained from the Royal Netherlands Meteorological Institute. An analysis was performed on all lithium serum levels not accounting for the intra-individual dependency of lithium serum levels. The association between season, temperature and both absolute lithium serum level and the frequency of potentially toxic serum levels was investigated. A mixed model analysis, accounting for intra-individual dependency of lithium serum levels, was performed.

RESULTS

A total of 41,102 lithium serum levels (3,054 patients) were included. A significant difference in mean lithium serum levels across seasons (p < 0.001) and temperature categories (p = 0.001) was found, peaking in summer [0.761 mmol/L, +/- standard error of the mean (SEM) 0.002] and at temperatures of 15-20 degrees C [0.762 mmol/L (+/- SEM 0.005)], and at a minimum in winter [0.748 mmol/L (+/- SEM 0.002)] and at <0 degrees C [0.741 mmol/L (+/- SEM 0.005)]. The relative frequency of potentially toxic serum levels significantly differed between seasons (p = 0.023, highest in winter), but not between temperature categories (p = 0.481). A significant positive association for intra-individual lithium serum level and season (p < 0.001) and temperature (p < 0.001) was established.

CONCLUSIONS

Season and environmental temperature have a statistically significant but therapeutically irrelevant effect on lithium serum levels.

Lithium concentrations in plasma of lithium-treated psychiatric patients in the Netherlands: commentary on Cusin et al

Seasonal variations in 68 psychiatric patients receiving prophylactic lithium treatment in the Netherlands between 1974 and 1994 were analyzed and compared with findings from Italy. Although lithium doses remained stable, there was a significant change in plasma levels of lithium, with values in spring and summer tending to exceed those in autumn and winter. These findings are similar to those reported in Italy, although the maximal seasonal change was approximately 5% in the Netherlands compared with approximately 10% in Italy. The difference could reflect the hotter summer climate in Italy, associated with increased perspiration. Future studies should measure perspiration levels directly.