Publications

The Study of Dementia in Swedish Twins 

Balbag MA, Pedersen NL, Gatz M (2014). Playing a musical instrument as a protective factor against dementia and cognitive impairment: A population-based twin study. International Journal of Alzheimer's Disease, Vol. 2014, Article ID 836748. article

Iacono D, Volkman I, Nennesmo I, Pedersen NL, Fratiglioni L, Johansson B, Karlsson D, Winblad B, Gatz M (2014). Neuropathologic assessment of dementia markers in identical and fraternal twins. Brain Pathology, 24, 317-333. article

Bokenberger K, Pedersen NL, Gatz M, Dahl AK (2013). The Type A behavior pattern and cardiovascular disease as predictors of Dementia. Health Psychology. [Epub ahead of print] abstract

Caracciolo B, Gatz M, Xu W, Marengoni A, Pedersen NL, Fratiglioni L (2013). Relationship of subjective cognitive impairment and cognitive impairment no dementia to chronic disease and multimorbidity in a nation-wide twin study. Journal of Alzheimer’s Disease, 36, 275-284. article

Pedersen NL, Christensen K, Dahl AK, Finkel D, Franz CE, Gatz M, Horwitz BN, Johansson B, Johnson W, Kremen WS, Lyons MJ, Malmberg B, McGue M, Neiderhiser JM, Petersen I, Reynolds CA (2013). IGEMS: the consortium on Interplay of Genes and Environment across Multiple Studies. Twin Research and Human Genetics, 16, 481-489. article

Gatz M, Pedersen NL (2013). Study of dementia in Swedish twins. Twin Research and Human Genetics, 16, 313-316. article

Dahl AK, Hassing LB, Fransson EI, Gatz M, Reynolds CA, Pedersen NL (2012). Body mass index across midlife and cognitive change in late life. International Journal of Obesity. [Epub ahead of print] article

Caracciolo B, Gatz M, Xu W, Marengoni A, Pedersen NL, Fratiglioni L (2012). Differential distribution of subjective and objective cognitive impairment in the population: A nation-wide twin-study. Journal of Alzheimer’s Disease, 29, 393-403. article

Andel R, Crowe M, Hahn E, Mortimer J, Pedersen N, Fratiglioni L, Johansson B, Gatz M (2012) Work-related stress may increase the risk of vascular dementia. Journal of the American Geriatrics Society, 60, 60-67. article

Feldman AL, Johansson ALV, Gatz M, Pedersen NL, Wirdefeldt K (2012). Accuracy and sensitivity of Parkinsonian disorder diagnoses in two Swedish national health registers. Neuroepidemiology, 38, 186–193. article

Brommelhoff JA, Spann BM, Go JL, Mack WJ, Gatz M (2011). Striatal hypodensities, not white matter hypodensities on CT, are associated with late-onset depression in Alzheimer‘s disease. Journal of Aging Research. [Epub ahead of print] article

Kurita K, Meyerowitz BE, Hall P, Gatz M (2011). Long-term cognitive impairment in older adult twins discordant for gynecologic cancer treatment. Journals of Gerontology: Medical Sciences, 66, 1343–1349. article

Wirdefeldt K, Gatz M, Reynolds CA, Prescott CA, Pedersen NL (2011). Heritability of Parkinson disease in Swedish twins: a longitudinal study. Neurobiology of Aging, 32, 1923. article

Reynolds CA, Gatz M, Pedersen NL, Prince JA (2011). An assessment of CETP sequence variation in relation to cognitive decline and dementia risk. International Journal of Molecular Epidemiology and Genetics, 2, 122–129. article 

Xu W, Atti AR, Gatz M, Pedersen NL, Johansson B, Fratiglioni L (2011). Midlife overweight and obesity increase late-life dementia risk: a population-based twin study. Neurology, 76, 1568-1574. article

Finkel D, Reynolds CA, Larsson M, Gatz M, Pedersen NL (2011). Both odor identification and ApoE contribute to normative cognitive aging. Psychology & Aging, 26, 872-883. article

Bennet AM, Reynolds CA, Eriksson UK, Hong MG, Hong MG, Blennow K, Gatz M, Alexeyenko A, Pedersen NL, Prince JA (2011). Genetic association of sequence variants near AGER/NOTCH4 and dementia. Journal of Alzheimer's Disease, 24, 475-484. article

Eriksson UK, Pedersen NL, Reynolds CA, Hong MG, Prince JA, Gatz M, Dickman PW, Bennet AM (2011). Associations of gene sequence variation and serum levels of C-reactive protein and interleukin-6 with Alzheimer's disease and dementia. Journal of Alzheimer's Disease 23, 361-369. article

Gatz M, Reynolds CA, Finkel D, Pedersen NL, Walters E (2010). Dementia in Swedish twins: Predicting incident cases. Behavior Genetics 40, 768-775. article

Bennet AM, Reynolds CA, Gatz M, Blennow K, Pedersen NL, Prince JA (2010). Pleiotropy in the presence of allelic heterogeneity: Alternative genetic models for the influence of APOE on serum LDL, CSF amyloid-β42, and dementia. Journal of Alzheimer's Disease 22, 129-134. article

Andel R, Crowe M, Feychting M, Pedersen NL, Fratiglioni L, Johansson B, Gatz M (2010). Work-related exposure to extremely low-frequency magnetic fields and dementia: Results from the population-based study of dementia in Swedish twins. The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences, 65, 1220-1227. article

Eriksson UK, Bennet AM, Gatz M, Dickman PW, Pedersen NL (2010). Nonstroke cardiovascular disease and risk of Alzheimer disease and dementia. Alzheimer Disease & Associated Disorders, 24, 213-219. article

Reynolds CA, Gatz M, Prince JA, Berg S, Pedersen NL (2010). Serum lipid levels and cognitive change in late life. Journal of the American Geriatrics Society, 58, 501-509. article

Reynolds CA, Hong MG, Eriksson UK, Blennow K, Wiklund F, Johansson B, Malmberg B, Berg S, Alexeyenko A, Gronberg H, Gatz M, Pedersen NL, Prince JA (2010). Analysis of lipid pathway genes indicates association of sequence variation near SREBF1/TOM1L2/ATPAF2 with dementia risk. Human Molecular Genetics, 19, 2068-2078 article

Hughes TF, Andel R, Small BJ, Borenstein AR, Mortimer JA, Wolk A, Johansson B, Fratiglioni L, Pedersen NL, Gatz M (2010). Midlife Fruit and Vegetable Consumption and Risk of Dementia in Late Life in Swedish Twins. American Journal of Geriatric Psychiatry, 18, 413-420. article

Reynolds CA, Hong MG, Eriksson UK, Blennow K, Johansson B, Malmberg B, Berg S, Gatz M, Pedersen NL, Bennet AM, Prince JA (2009). Sequence variation in SORL1 and dementia risk in Swedes. Neurogenetics, 11, 139-142. article

Kendler KS, Gardner CO, Fiske A, Gatz M (2009). Major depression and coronary artery disease in the Swedish twin registry: phenotypic, genetic, and environmental sources of comorbidity. Archives of General Psychiatry, 66, 857-863. article

Hassing LB, Dahl A, Thorvaldsson B, Berg S, Gatz M, Pedersen NL, Johansson B (2009). Overweight in midlife and risk of dementia: A 40-year follow-up study. International Journal of Obesity, 33, 893-898. article

Reynolds CA, Hong MG, Eriksson UK, Blennow K, Bennet AM, Johansson B, Malmberg B, Berg S, Wiklund F, Gatz M, Pedersen NL, Prince JA (2009). A survey of ABCA1 sequence variation confirms association with dementia. Human Mutation, 30, 1348-1354. article

Brommelhoff JA, Gatz M, Johansson B, McArdle JJ, Fratiglioni L, Pedersen NL (2009). Depression as a risk factor or prodromal feature for dementia? Findings in a population-based sample of Swedish twins. Psychology and Aging, 24, 373-384. article

Dahl A, Hassing LB, Fransson E, Berg S, Gatz M, Reynolds CA, Pedersen NL (2009). Being overweight in midlife is associated with lower cognitive ability and steeper cognitive decline in later life. The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences, 65, 57-62. article

Xu W, Qiu C, Gatz M, Pedersen NL, Johansson B, Fratiglioni L (2009). Mid-and late-life diabetes in relation to the risk of dementia: A population-based twin study. Diabetes, 58, 71-77. article

Wirdefeldt K, Gatz M, Bakaysa SL, Fiske A, Glensburg M, Petzinger GM, Widner H, Lew MF, Welsh M, Pedersen NL (2008). Complete ascertainment of Parkinson disease in the Swedish Twin Registry. Neurobiology of Aging, 29, 1765-1773. article

Hong M, Reynolds C, Gatz M, Johansson B, Palmer JC, Gu HF, et al. (2008). Evidence that the gene encoding insulin degrading enzyme influences human lifespan. Human Molecular Genetics, 17, 2370-2378. article

Andel R, Crowe M, Pedersen NL, Fratiglioni L, Johansson B, Gatz M (2008). Physical exercise at midlife and risk of dementia three decades later: A population-based study of Swedish twins. The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences, 63, 62-66. article

Blom ES, Holmans P, Arepalli S, Adighibe O, Hamshere ML, Gatz M, Pedersen NL, Bergem AL, Owen MJ, Hollingworth P, Goate A, Williams J, Lannfelt L (2008). Does APOE explain the linkage of Alzheimer's disease to chromosome 19q13? American Journal of Medical Genetics Part B: Neuropsychiatric Genetics, 147B, 778-783. article

Eriksson UK, Gatz M, Dickman PW, Fratiglioni L, Pedersen NL (2008). Asthma, eczema, rhinitis and the risk for dementia. Dementia & Geriatric Cognitive Disorders, 25, 148-156. article

Fiske A, Gatz M (2007). The Apartment Test: Validity of a memory measure. Aging, Neuropsychology and Cognition, 14, 441-461. article

Crowe M, Andel R, Pedersen NL, Gatz M (2007). Do work-related stress and reactivity to stress predict dementia more than 30 years later? Alzheimer Disease and Associated Disorders, 21, 205-209. abstract

Gatz M, Mortimer JA, Fratiglioni L, Johansson B, Berg S, Andel R, Crowe M, Fiske A, Reynolds CA, Pedersen NL (2007). Accounting for the relationship between low education and dementia: A twin study. Physiology & Behavior, 92, 232-237. article

Gatz M (2007). Genetics, dementia and the elderly. Current Directions in Psychological Science, 16, 123-127. article

Crowe M, Andel R, Pedersen NL, Fratiglioni L, Gatz M (2006). Personality and risk of cognitive impairment 25 years later. Psychology and Aging, 21, 573-580. abstract

Gatz M, Prescott CA, Pedersen NL (2006). Lifestyle risk and delaying factors. Alzheimer Disease and Associated Disorders, 20, S84-S88. abstract

Gatz M, Mortimer JA, Fratiglioni L, Johansson B, Berg S, Reynolds CA, Pedersen NL (2006). Potentially modifiable risk factors for dementia in identical twins. Alzheimer's & Dementia, 2, 110-117. article

Gatz M, Pedersen NL (2006). Commentary on "The NIH cognitive and emotional health project: Report of the critical evaluation study committee." What can be concluded? Alzheimer's & Dementia, 2, 91-92. article

Reynolds CA, Fiske A, Fratiglioni L, Pedersen NL, Gatz M (2006). Heritability of an age-dependent categorical phenotype: Cognitive dysfunction. Twin Research and Human Genetics, 9, 17-23. abstract

Reynolds CA, Prince JA, Feuk L, Gatz M, Brookes AJ, Pedersen NL (2006). Longitudinal memory performance during normal aging: twin association models of APOE and other Alzheimer candidate genes. Behavior Genetics, 36, 1-10. article

Gatz M, Reynolds CA, Fratiglioni L, Johansson B, Mortimer JA, Berg S, Fiske A, Pedersen NL (2006). Role of genes and environments for explaining Alzheimer’s disease. Archives of General Psychiatry, 63, 168-174. article

Read S, Pedersen NL, Gatz M, Berg S, Vuoksimaa E, Malmberg B, Johansson B, McClearn GE (2006). Sex differences after all those years? Heritability of cognitive abilities in old age. Journal of Gerontology: Psychological Sciences, 61B, P137-P143. article

Reynolds CA, Jansson M, Gatz M, Pedersen NL (2006). Longitudinal change in memory performance associated with HTR2A polymorphism. Neurobiology of Aging, 27, 150-154. article

Gatz M, Fiske A, Reynolds CA, Johansson B, Fratiglioni L, Pedersen NL (2005). Performance on neurocognitive tests by co-twins to dementia cases compared to normal control twins. Journal of Geriatric Psychiatry and Neurology, 18, 202-207. article

Andel R, Crowe M, Pedersen NL, Mortimer J, Crimmins E, Johansson B, Gatz M (2005). Complexity of work and risk of Alzheimer's disease: A population-based study of Swedish twins. Journals of Gerontology: Psychology Sciences, 60, 251-258. article

Fiske A, Gatz M, Aadnoy B, Pedersen NL(2005). Assessing age of dementia onset: Validity of informant reports. Alzheimer Disease and Associated Disorders, 19, 128-134. abstract

Rasgon NL, Magnusson C, Johansson ALV, Pedersen NL, Elman S, Gatz M (2005). Endogenous and exogenous hormone exposure and risk of cognitive impairment in Swedish twins: A preliminary study. Psychoneuroendocrinology, 30, 558-567. article

Heflin LH, Meyerowitz BE, Hall P, Lichtenstein P, Johansson B, Pedersen NL, Gatz M (2005). Re: Cancer as a risk factor for long-term cognitive deficits and dementia. Journal of the National Cancer Institute, 97, 1550-1551. article

Reynolds CA, Turner A, Gatz M, Pedersen NL (2005). Comparative rating measures of health and environmental exposures: how well do twins agree. Twin Research and Human Genetics, 8, 113-119. abstract

Gatz M (2005). Educating the brain to avoid dementia: Can mental exercise prevent Alzheimer disease? PLoS Medicine, 2, 38-40. article

Wirdefeldt K, Gatz M, Pawitan Y, Pedersen NL (2005). Risk and protective factors for Parkinson's disease: A study in Swedish twins. Annuals of Neurology, 57, 27-33. article

Reynolds CA, Finkel D, McArdle JJ, Gatz M, Berg S, Pedersen NL (2005). Quantitative genetic analysis of latent growth curve models of cognitive abilities in adulthood. Developmental Psychology, 41, 3-16. abstract

Gatz M, Fratiglioni L, Johansson B, Berg S, Mortimer JA, Reynolds CA, Fiske A, Pedersen NL (2005). Complete ascertainment of dementia in the Swedish Twin Registry: the HARMONY study.  Neurobiology of Aging, 26, 439-447. article

Katzov H, Bennet A, Kehoe P, Wiman B, Gatz M, Blennow K, Lenhard B, Pedersen NL, deFaire U, Prince JA (2004). A cladistic model of ACE sequence variation with implications for myocardial infarction, Alzheimer’s disease, and obesity. Human Molecular Genetics, 13, 2647-2657. article

Blomqvist M, Silburn PA, Buchanan DD, Andreasen N, Blennow K, Pedersen NL, Brookes AJ, Mellick GD, Prince JA (2004). Sequence variation in the proximity of IDE may impact age at onset of both Parkinson's disease and Alzheimer's disease. Neurogenetics, 5, 115-119. article

Jin Y-P, Gatz M, Johansson B, Pedersen NL (2004). Sensitivity and specificity of dementia coding in two Swedish disease registries. Neurology, 63, 739-741. article

Pedersen NL, Gatz M, Berg S, & Johansson B (2004).  How heritable is Alzheimer's disease late in life? Findings from Swedish Twins.  Annuals of Neurology, 55, 180-185. article

Kehoe PG, Katzov H, Andreasen N, Gatz M, Wilcock GK, Cairns NJ, Palmgren J, deFaire U, Brookes AJ, Pedersen NL, Blennow K, Prince JA (2004). Common variants of ACE contribute to variable age-at-onset of Alzheimer’s disease. Human Genetics, 114, 478-483. article

Katzov H, Chalmers K, Palmgren J, Andreasen N, Johansson B, Cairns NJ, Gatz M, Wilcock GK, Love S, Pedersen NL, Brookes AJ, Blennow K, Kehoe PG, Prince JA (2004).  Genetic variants of ABCA1 modify Alzheimer disease risk and quantitative traits related to beta-amyloid metabolism. Human Mutation, 23, 358-367. article

Johansson A, Katzov H, Zetterberg H, Feuk L, Johansson B, Bogdanovic N, Andreasen N, Lenhard B, Brookes AJ, Pedersen NL, Blennow K, Prince JA (2004). Variants of CYP46A1 may interact with age and APOE to influence CSF Abeta42 levels in Alzheimer's disease. Human Genetics, 114, 581-587. article

Prince JA, Feuk L, Gu HF, Johansson B, Gatz M, Blennow K, Brookes AJ (2003).  Genetic variation in a haplotype block spanning IDE influences Alzheimer disease.  Human Mutation, 22, 363-371. article

Finkel D, Reynolds CA, McArdle JJ, Gatz M, Pedersen NL (2003). Latent growth curve analyses of accelerating decline in cognitive abilities in adulthood. Developmental Psychology, 39, 535-550. abstract

Crowe M, Andel R, Pedersen NL, Johansson B, Gatz M (2003). Does participation in leisure activities lead to reduced risk of Alzheimer's disease? A Prospective study of Swedish twins. Journals of Gerontology: Psychological Sciences, 58B, P249-P255. article

Gatz M, Fiske A, Reynolds CA, Wetherell JL, Johansson B, Pedersen NL (2003). Sex differences in genetic risk for dementia. Behavior Genetics, 33, 95-105. article

Ripatti S, Gatz M, Pedersen NL, Palmgren J (2003).  A three-state frailty model for age at onset of dementia and death in Swedish twins. Genetic Epidemiology, 24, 139-149. article

Hassing LB, Johansson B, Nilsson SE, Berg S, Pedersen NL, Gatz M, McClearn G (2002).  Diabetes mellitus is a risk factor for vascular dementia, but not for Alzheimer's disease: A population-based study of the oldest-old. International Psychogeriatrics, 14, 239-248. abstract

Gatz M, Reynolds CA, John R, Johansson B, Mortimer JA, Pedersen NL (2002). Telephone screening to identify potential dementia cases in a population-based sample of older adults. International Psychogeriatrics, 14, 273-289. abstract

Reynolds CA, Finkel D, Gatz M, Pedersen NL (2002). Sources of influences on rate of cognitive change over time in Swedish twins: An application of latent growth models. Experimental Aging Research, 28, 407-433. article

Watari K, Gatz M (2002). Dementia: Cross-cultural perspective on risk factors. Generations, 26, 32-38.

Wetherell JL, Reynolds CA, Gatz M, Pedersen NL (2002). Anxiety, cognitive performance and cognitive decline in normal aging. Journals of Gerontology: Psychological Sciences, 57B, P246-P255. article

Reynolds CA, Gatz M, Pedersen NL (2002). Individual variation for cognitive decline: Quantitative methods for describing patterns of change. Psychology and Aging, 17, 271-287. abstract

Pedersen NL, Posner SF, Gatz M (2001). Multiple threshold models for genetic influences on age of onset for Alzheimer’s disease: Findings in Swedish twins. American Journal of Medical Genetics, 105, 724-728. article

Andel R, Gatz M, Pedersen NL, Reynolds CA, Johansson B, Berg S (2001). Deficits in controlled processing may predict dementia: A twin study. Journals of Gerontology: Psychological Sciences, 56, P347-P355. article

Gatz M, Svedberg P, Pedersen NL, Mortimer JA, Berg S, Johansson B (2001). Education and the risk of Alzheimer's disease: Findings from the Study of Dementia in Swedish Twins. Journals of Gerontology: Psychological Sciences, P292-P300. article

Gatz M, Pedersen NL, Crowe M, Fiske A (2000). Defining discordance in twin studies of risk and protective factors for late life disorders.  Twin Research, 3, 159-164. abstract

Rowe JW, Gatz M (2000). Implications of genetic knowledge for public policy. Generations, 24, 79-83.

Reynolds CA, Wetherell JL, Gatz M (1999). Heritability of Alzheimer's disease.  In B.Vellas & L.J. Fitten (Eds.), Research and practice in Alzheimer's disease and other dementias (Vol. 2) (pp. 175-191) New York: Springer Publishing.

Posner SF, Pedersen NL, Gatz M (1999). Application of life table analysis to the onset of dementia in a genetically informative design. Neuropsychiatric Genetics, 88, 207-210. article

Pedersen NL, Miller BL, Wetherell JL, Vallo J, Toga AW, Knutson N, Mehringer CM, Small GW, Gatz M (1999).  Neuroimaging findings in twins discordant for Alzheimer's disease.  Dementia and Geriatric Cognitive Disorders, 10, 51-58. article

Wetherell JL, Gatz M, Johansson B, Pedersen NL (1999).  History of depression and other psychiatric illness as risk factors for Alzheimer's disease in a twin sample.  Alzheimer Disease and Associated Disorders, 13, 47-52. abstract

Pedersen NL, Berg S, Johansson B, Johansson K, Viitanen M, Winblad B, Gatz M (1998).  Genetiska Faktorer ligger ofta bakom Alzheimer's sjukdom: Stor tvillingstudie skall klarlagga sambanden arv-miljo. [Genetic factors are often found in Alzheimer disease. An extensive twin study to clarify the heredity-environment relationship].  Lakartindningen, 95, 2585-2588. abstract

Feychting M, Pedersen NL, Svedberg P, Floderus B, Gatz M (1998).  Dementia and occupation exposure to magnetic fields.  Scandinavian Journal of Work, Environment & Health, 24, 46-53. abstract

Gatz M, Pedersen NL, Berg S, Johansson B, Johannson K, Mortimer JA, Posner SF, Viitanen M, Winblad B, Ahlbom A (1997). Heritability for Alzheimer's Disease: The study of dementia in Swedish twins. Journal of Gerontology: Medical Sciences, 52A, M117-125. article

Gatz M, Pedersen NL (1996).  Use of twin samples to estimate the heritability of Alzheimer's disease:  A methodological note.  Alzheimer's Research, 2, 229-231.

Pedersen NL, Reynolds CA, Gatz M (1996). Sources of covariation among Mini-Mental State Examination scores, education and cognitive abilities. Journal of Gerontology: Psychological Sciences, 51B, P55-P63. article

Pedersen NL (1996). Gerontological behavior genetics. In J. E. Birren & K. W. Schaie (Eds.), Handbook of the psychology of aging, Fourth edition. (pp. 59-77). San Diego: Academic Press.

Pedersen NL, Posner SF, Gatz M (1995). Twin studies as tools for bridging the gap between genetics and epidemiology of dementia. In M. Bergener & S. I. Finkel (Eds.), Treating Alzheimer's and other dementias: Clinical application of recent research advances. (pp.527-544). New York: Springer Publishing Co.

Lannfelt L, Pedersen NL, Lilius L, Axelman K, Johansson K, Viitanen M, Gatz M (1995). Apolipoprotein epsilon 4 allele in Swedish twins and siblings with Alzheimer's disease. Alzheimer Disease & Associated Disorders, 9, 166-169. abstract

Johansson B, Gatz M, Berg S, Pedersen N (1995). Heterogeneity of impairment in dementia: Data from the Study of Dementia in Swedish Twins. In M. Bergener, Brocklehurst, J. C., & Finkel, S. I. (Ed.), Aging, health, and healing. (pp. 74-79). New York: Springer Publishing Co.

Gatz M, Reynolds C, Nikolic J, Lowe B, Karel M, Pedersen N (1995). An empirical test of telephone screening to identify potential dementia cases. International Psychogeriatrics, 7, 429-437. abstract

Gatz M (1995). Questions that aging puts to preventionists. In L. Bond, S. Cutler & A. Grams (Eds.), Promoting successful and productive aging (pp. 36-50). Newbury Park: Sage.

Gatz M, Lowe B, Berg S, Mortimer J, Pedersen N (1994). Dementia: Not just a search for the gene. The Gerontologist, 34, 251-255. article

Breitner JCS, Gatz M, Bergem ALM, Christian JC, Mortimer JA, McClearn GE, Heston LL, Welsh KA, Anthony JC, Folstein MF, Radebaugh TS (1993). Use of twin cohorts for research in Alzheimer's disease. Neurology, 43, 261-267. abstract

Pedersen NL, Gatz M, Winblad B, Pearson CG, Berg S (1989). Dementias in Swedish twins. In K. Iqbal, H. M. Wisniewski, & B. Winblad (Eds.), Alzheimer's disease and related disorders (Vol. 317, pp. 217 222). New York: Alan R. Liss.