etters to the Editor
Letters to the Editor are welcomed and wil bepublished, iffound suitable, as space pernits. Submission of a Letter to the Editor constitutes permission for its publication in the Journal. Letters should not duplicate similar material being submitted orpublished elsewhere. Letters refemng to a recent Journal article should be received within three months of the article's publication. The editors reserve the nightto edit and abridge letters, topublish replies, and to solicit responses from authors and others. Letters should be submitted in duplicate, double-spaced (including references), and should not exceed 400 words.
Longevity and Left-Handedness There has been speculation that human dextrals (right handers) live longer than sinistrals (left handers). This supposition is based on two lines of evidence. The first is that the proportion of people professing to be dextral increases with age, presumably because sinistrals are dying at younger ages than dextrals.1 The second line of evidence is based on a study using
professional baseball players (all males) whose handedness is a matter of public record.2 From these lines of evidence, Halpem and Coren suggest that the decreased longevity in sinistrals can be explained by Increased prenatal and perinatal stressors, genetic and intrauterine hormonal effects on the immune system, and a higher incidence of accidents for sinistrals.23 The data for the first line of evidence are indirect and gleaned from the literature. Gender was ignored since genderage interactions were not significant. The Health and Nutrition Examination Survey (HANES), conducted by the National Center for Health Statistics4,5 contains April 1991, Vol. 81, No. 4
data which allow direct determination of the relationships among age, gender, laterality, and longevity. In the HANES sample, the proportion of sinistral males was higher than the proportion of sinistral females regardless of age group (overall 9.53 percent vs 7.35 percent, 95% CI for difference = 0.51%, 3.88%) although the percent of sinistrals generally declined with increasing age in both males and females. The vital status (age if living or age at death if dead) and sex were extracted for those patients for whom laterality was known and 10-year follow-up information was available. Complete infornation on these variables was known for 2,386 subjects, 93.7 percent of whom were right handed. Ambidextrous persons were excluded. At follow-up, 346 dextrals were known to be dead and, 1,889 were known to be alive. Twenty sinistrals were dead and 131 were alive at follow-up. A Cox proportional hazards model7 for laterality, after controlling for sex, was tested. This model showed that hand laterality was not a significant factor in longevity (P > 0.88) although sex was (P < .001). The HANES data, like the indirect data from the literature, show decreasing sinistrality with advancing age. This phenomenon is consistent with the hypothesis that sinistrals die at younger ages than dextrals. However, the Cox model for longevity would seem to present stronger evidence against the hypothesis that dextrals live longer than sinistrals than the changing incidence of sinistrality with increasing age presents for such a hypothesis. It seems premature to conclude that laterality is an important determinant of longevity. O K V. Kuhemeier Division of Rehabilitation Medicine, Johns Hopkins University, Baltimore, Maryland 21239
References 1. Poroc C, Coren S: Lateral Preferences and Human Behavior. New York: Springer, 1981. 2. Halpern DF, Coren S: Do right-handers live longer? Nature 1988; 333:213. 3. Coren S: Left-handedness and accidentrelated injury risk. Am J Public Health 1989; 79:1040-1041. 4. National Center for Health Statistics: DHEW Pub. No. HSM 73-1310. Washington, DC: Govt Printing Office, reprinted 1979. 5. Madans JH, Kleinman JC, Cox CS, et at 10 years after NHANES I: Report of initial follow-up, 1982-1984. Public Health Rep 1986; 101:465-473. 6. Wood EK: Nature 1988; 335:212. 7. Cox DR: Regression models and life tables. J R Stat Soc B 1972; 34:187-220.
Congenital Syphilis Not an Artifact We thank Drs. Htoo and Schultz for their letter' concerning a possible misinterpretation of our article on rates of congenital syphilis.' As in New York City, the epidenic of congenital syphilis in Los Angeles is not an artifact caused by a change in case definition. Using the 1988 Centers forDisease Control (CDC) criteria for congenital syphilis,3 cases in Los Angeles increased 92 percent to 393 between 1987 and 1988 and increased another 34 percent in 1989 to a total of 528. These figures underestimate the true number since all fetal deaths due to syphilis have not been included. Seronegative infants whose mothers had untreated syphilis at delivery (73 infants in 1989), now considered cases by the revised CDC surveillance criteria,4 were also not counted. Had Los Angeles continued to use only the modified Kaufmans' criteria and counted only symptomatic cases, a different impression of the epidemic would have emerged. Symptomatic cases de-
American Journal of Public Health 513
Letters to the Editor are welcomed and wil bepublished, iffound suitable, as space pernits. Submission of a Letter to the Editor constitutes permission for its publication in the Journal. Letters should not duplicate similar material being submitted orpublished elsewhere. Letters refemng to a recent Journal article should be received within three months of the article's publication. The editors reserve the nightto edit and abridge letters, topublish replies, and to solicit responses from authors and others. Letters should be submitted in duplicate, double-spaced (including references), and should not exceed 400 words.
Longevity and Left-Handedness There has been speculation that human dextrals (right handers) live longer than sinistrals (left handers). This supposition is based on two lines of evidence. The first is that the proportion of people professing to be dextral increases with age, presumably because sinistrals are dying at younger ages than dextrals.1 The second line of evidence is based on a study using
professional baseball players (all males) whose handedness is a matter of public record.2 From these lines of evidence, Halpem and Coren suggest that the decreased longevity in sinistrals can be explained by Increased prenatal and perinatal stressors, genetic and intrauterine hormonal effects on the immune system, and a higher incidence of accidents for sinistrals.23 The data for the first line of evidence are indirect and gleaned from the literature. Gender was ignored since genderage interactions were not significant. The Health and Nutrition Examination Survey (HANES), conducted by the National Center for Health Statistics4,5 contains April 1991, Vol. 81, No. 4
data which allow direct determination of the relationships among age, gender, laterality, and longevity. In the HANES sample, the proportion of sinistral males was higher than the proportion of sinistral females regardless of age group (overall 9.53 percent vs 7.35 percent, 95% CI for difference = 0.51%, 3.88%) although the percent of sinistrals generally declined with increasing age in both males and females. The vital status (age if living or age at death if dead) and sex were extracted for those patients for whom laterality was known and 10-year follow-up information was available. Complete infornation on these variables was known for 2,386 subjects, 93.7 percent of whom were right handed. Ambidextrous persons were excluded. At follow-up, 346 dextrals were known to be dead and, 1,889 were known to be alive. Twenty sinistrals were dead and 131 were alive at follow-up. A Cox proportional hazards model7 for laterality, after controlling for sex, was tested. This model showed that hand laterality was not a significant factor in longevity (P > 0.88) although sex was (P < .001). The HANES data, like the indirect data from the literature, show decreasing sinistrality with advancing age. This phenomenon is consistent with the hypothesis that sinistrals die at younger ages than dextrals. However, the Cox model for longevity would seem to present stronger evidence against the hypothesis that dextrals live longer than sinistrals than the changing incidence of sinistrality with increasing age presents for such a hypothesis. It seems premature to conclude that laterality is an important determinant of longevity. O K V. Kuhemeier Division of Rehabilitation Medicine, Johns Hopkins University, Baltimore, Maryland 21239
References 1. Poroc C, Coren S: Lateral Preferences and Human Behavior. New York: Springer, 1981. 2. Halpern DF, Coren S: Do right-handers live longer? Nature 1988; 333:213. 3. Coren S: Left-handedness and accidentrelated injury risk. Am J Public Health 1989; 79:1040-1041. 4. National Center for Health Statistics: DHEW Pub. No. HSM 73-1310. Washington, DC: Govt Printing Office, reprinted 1979. 5. Madans JH, Kleinman JC, Cox CS, et at 10 years after NHANES I: Report of initial follow-up, 1982-1984. Public Health Rep 1986; 101:465-473. 6. Wood EK: Nature 1988; 335:212. 7. Cox DR: Regression models and life tables. J R Stat Soc B 1972; 34:187-220.
Congenital Syphilis Not an Artifact We thank Drs. Htoo and Schultz for their letter' concerning a possible misinterpretation of our article on rates of congenital syphilis.' As in New York City, the epidenic of congenital syphilis in Los Angeles is not an artifact caused by a change in case definition. Using the 1988 Centers forDisease Control (CDC) criteria for congenital syphilis,3 cases in Los Angeles increased 92 percent to 393 between 1987 and 1988 and increased another 34 percent in 1989 to a total of 528. These figures underestimate the true number since all fetal deaths due to syphilis have not been included. Seronegative infants whose mothers had untreated syphilis at delivery (73 infants in 1989), now considered cases by the revised CDC surveillance criteria,4 were also not counted. Had Los Angeles continued to use only the modified Kaufmans' criteria and counted only symptomatic cases, a different impression of the epidemic would have emerged. Symptomatic cases de-
American Journal of Public Health 513
