Trace lithium is inversely associated with male suicide after adjustment of climatic factors.

Previously, we showed the inverse association between lithium in drinking water and male suicide in Kyushu Island. The narrow variation in meteorological factors of Kyushu Island and a considerable amount of evidence regarding the role of the factors on suicide provoked the necessities of adjusting the association by the wide variation in sunshine, temperature, rain fall, and snow fall. To keep the wide variation in meteorological factors, we combined the data of Kyushu (the southernmost city is Itoman, 26°) and Hokkaido (the northernmost city is Wakkanai, 45°). Multiple regression analyses were used to predict suicide SMRs (total, male and female) by lithium levels in drinking water and meteorological factors. After adjustment of meteorological factors, lithium levels were significantly and inversely associated with male suicide SMRs, but not with total or female suicide SMRs, across the 153 cities of Hokkaido and Kyushu Islands. Moreover, annual total sunshine and annual mean temperature were significantly and inversely associated with male suicide SMRs whereas annual total rainfall was significantly and directly associated with male suicide SMRs. The limitations of the present study include the lack of data relevant to lithium levels in food and the proportion of the population who drank tap water and their consumption habits. The present findings suggest that trace lithium is inversely associated with male but not female suicide after adjustment of meteorological factors.

Shiotsuki I ，Terao T ，Ishii N ，Takeuchi S ，Kuroda Y ，Kohno K ，Mizokami Y ，Hatano K ，Tanabe S ，Kanehisa M ，Iwata N ，Matusda S ... -  《-》

Low risk of male suicide and lithium in drinking water.

Recently, several epidemiologic studies reported that lithium in drinking water may be associated with lower rates of suicide mortality at the population level, but other studies failed to confirm the association. The objective of the present study is to determine whether lithium in drinking water is associated with lower suicide rate after adjustment of potential confounding factors. From 2010 to 2013, 274 mean lithium levels of 434 lithium samples in drinking water were examined in relation to suicide standardized mortality ratios (SMRs) in 274 municipalities of Kyushu Island in Japan. Weighted least squares regression analysis adjusted for the size of each population was used to investigate the association of lithium levels with suicide SMRs. The associations of lithium levels in drinking water with suicide SMRs (total, male, and female) were investigated adjusting for proportion of elderly people, proportion of 1-person households, proportion of people with college education or more, and proportion of people engaging in primary industry (adjusted model 1), and further adjustment was performed with overall unemployment rate, annual marriage rate, annual mean temperature, and annual postal savings per person (adjusted model 2). Lithium levels in drinking water were significantly (β = -.169, P = .019) and inversely associated with male suicide SMRs but not total or female SMRs in the adjusted model 2. The present findings suggest that lithium in drinking water may be associated with the low risk of male suicide in the general population. Further studies are required to confirm these findings and investigate gender differences.

Ishii N ，Terao T ，Araki Y ，Kohno K ，Mizokami Y ，Shiotsuki I ，Hatano K ，Makino M ，Kodama K ，Iwata N ... -  《-》

Association between lithium in tap water and suicide mortality rates in Miyazaki Prefecture.

Kozaka N ，Takeuchi S ，Ishii N ，Terao T ，Kuroda Y ... -  《-》

Lithium in drinking water and suicide prevention: The largest nationwide epidemiological study from Japan.

The aims of the present study thus were (a) to further investigate the association between lithium levels in drinking water and suicide rates by adjusting relevant factors using the so far largest available dataset in Japan, (b) to confirm sex differences, (c) to estimate the effects of long-term exposure to trace lithium, (d) to investigate the effects of drinking bottled instead of tap water, and (e) to exploratorily investigate which lithium levels may be associated with lower suicide rates. Mean lithium levels in drinking water of all 808 cities and wards (ie, 785 cities of 46 prefectures and 23 wards of Tokyo) in Japan were examined in relation to mean suicide standardized mortality ratios (SMRs) during the 7 years from 2010 to 2016. Multiple regression analyses adjusted for the size of each population were used to investigate the association of lithium levels with suicide SMRs with adjustments for relevant factors. The adjusted model showed significant inverse associations of lithium levels with total and male SMRs, but not with female SMRs. Neither the proportion of residents who continued to live in the same city nor the consumption of bottled water changed the association between lithium levels and suicide SMRs. Finally, it was 30 μg/L or more that was associated with lower suicide SMRs. The present findings reconfirm the inverse association between lithium levels in drinking water and suicide rates particularly in the male population.

Kugimiya T ，Ishii N ，Kohno K ，Kanehisa M ，Hatano K ，Hirakawa H ，Terao T ... -  《-》

Re-analysis of the association of temperature or sunshine with hyperthymic temperament using lithium levels of drinking water.

The Japanese archipelago stretches over 4000km from north to south and has four large islands: Hokkaido, Honshu, Shikoku, and Kyushu. Previously, using the Temperament Evaluation of Memphis, Pisa, Paris and San Diego-auto questionnaire version (TEMPS-A), we compared the hyperthymic scores of residents in Sapporo, Obihiro, Takaoka, Koshigaya, and Oita cities (which are located at latitudes of 43°N, 42°N, 36°N, 36°N and 33°N with various combinations of ambient temperament and sunshine in Japan, respectively). We found that latitude predicted significant variance in hyperthymic temperament, and that ambient temperature, but not sunshine, significantly affected hyperthymic temperament scores. However, the analysis failed to consider the effects of naturally occurring low-dose lithium on temperament. In addition to the TEMPS-A data previously collected, we measured lithium levels of the five cities. The effect of temperature, sunshine, and lithium levels on hyperthymic temperament was analyzed for the five cities. A stepwise multiple regression analysis revealed that lithium levels as well as latitude, but not temperature or sunshine, predicted significant variance in hyperthymic temperament scores. Hyperthymic temperament scores were significantly and positively associated with lithium levels whereas they were significantly and negatively associated with latitude. The light, temperature, lithium exposure that residents actually received was not measured. The number of regions studied was limited. The findings might not be generalized to residents across Japan or other countries. The present findings suggest that lithium in drinking water may positively maintain hyperthymic temperament, and that latitude may negatively maintain it.

Matsuzaki H ，Terao T ，Inoue T ，Takaesu Y ，Ishii N ，Kohno K ，Takeshima M ，Baba H ，Honma H ... -  《-》